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  • 1
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    American Physical Society (APS)
    Publikationsdatum: 2014-12-18
    Beschreibung: Author(s): Aurélien Barrau, Carlo Rovelli, and Francesca Vidotto Quantum gravity effects could make a black hole explode in a time shorter than the Hawking radiation time, via local tunneling through a white hole solution. Here we estimate the size of a primordial black hole exploding today via this process, using a simple generic model. Fast radio bursts, strong... [Phys. Rev. D 90, 127503] Published Wed Dec 17, 2014
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  • 2
    Publikationsdatum: 2014-11-08
    Beschreibung: Author(s): Kōji Uryū, Eric Gourgoulhon, Charalampos M. Markakis, Kotaro Fujisawa, Antonios Tsokaros, and Yoshiharu Eriguchi Stationary and axisymmetric solutions of relativistic rotating stars with strong mixed poloidal and toroidal magnetic fields are obtained numerically. Because of the mixed components of the magnetic field, the underlying stationary and axisymmetric spacetimes are no longer circular. These configurat... [Phys. Rev. D 90, 101501] Published Fri Nov 07, 2014
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  • 3
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    American Physical Society (APS)
    Publikationsdatum: 2014-12-04
    Beschreibung: Author(s): Antonin Coutant and Renaud Parentani To identify what replaces the key notion of black hole horizon when working with theories which break Lorentz invariance at high energy, we study the modes responsible for the Hawking effect in the presence of high frequency dispersion. We show that they are regularized across the horizon over a sho... [Phys. Rev. D 90, 121501] Published Wed Dec 03, 2014
    Schlagwort(e): General relativity, gravitation
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  • 4
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    American Physical Society (APS)
    Publikationsdatum: 2014-01-23
    Beschreibung: Author(s): José Luis Jaramillo Black hole horizon sections, modeled as marginally outer trapped surfaces (MOTS), possess a notion of stability admitting a spectral characterization. Specifically, the “principal eigenvalue” λo of the MOTS-stability operator (an elliptic operator on horizon sections) must be nonnegative. We discuss... [Phys. Rev. D 89, 021502] Published Wed Jan 22, 2014
    Schlagwort(e): General relativity, gravitation
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  • 5
    Publikationsdatum: 2014-01-23
    Beschreibung: Author(s): D. Glavan, T. Prokopec, and V. Prymidis In this paper we study a massless, minimally coupled scalar field in a Friedmann-Lemaître-Robertson-Walker space-time with periods of different constant deceleration parameter. We assume the Bunch-Davies vacuum during inflation and then use a sudden matching approximation to match it onto a radiatio... [Phys. Rev. D 89, 024024] Published Wed Jan 22, 2014
    Schlagwort(e): General relativity, gravitation
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  • 6
    Publikationsdatum: 2014-01-23
    Beschreibung: Author(s): Anna Heffernan, Adrian Ottewill, and Barry Wardell In a previous paper, we computed expressions for the Detweiler-Whiting singular field of point scalar, electromagnetic and gravitational charges following a geodesic of the Schwarzschild spacetime. We now extend this to the case of equatorial orbits in Kerr spacetime, using coordinate and covariant ... [Phys. Rev. D 89, 024030] Published Wed Jan 22, 2014
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  • 7
    Publikationsdatum: 2014-03-14
    Beschreibung: Author(s): Andrea Taracchini, Alessandra Buonanno, Yi Pan, Tanja Hinderer, Michael Boyle, Daniel A. Hemberger, Lawrence E. Kidder, Geoffrey Lovelace, Abdul H. Mroué, Harald P. Pfeiffer, Mark A. Scheel, Béla Szilágyi, Nicholas W. Taylor, and Anil Zenginoglu Gravitational waves emitted by black-hole binary systems have the highest signal-to-noise ratio in LIGO and Virgo detectors when black-hole spins are aligned with the orbital angular momentum and extremal. For such systems, we extend the effective-one-body inspiral-merger-ringdown waveforms to gener... [Phys. Rev. D 89, 061502] Published Thu Mar 13, 2014
    Schlagwort(e): General relativity, gravitation
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  • 8
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    American Physical Society (APS)
    Publikationsdatum: 2014-03-21
    Beschreibung: Author(s): William E. East, Fethi M. Ramazanoğlu, and Frans Pretorius We study the superradiant scattering of gravitational waves by a nearly extremal black hole (dimensionless spin a=0.99) by numerically solving the full Einstein field equations, thus including backreaction effects. This allows us to study the dynamics of the black hole as it loses energy and angular... [Phys. Rev. D 89, 061503] Published Thu Mar 20, 2014
    Schlagwort(e): General relativity, gravitation
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  • 9
    Publikationsdatum: 2014-02-25
    Beschreibung: Author(s): Hirotada Okawa, Vitor Cardoso, and Paolo Pani The nonlinear instability of anti-de Sitter spacetime has recently been established with the striking result that generic initial data collapse to form black holes. This outcome suggests that confined matter might generically collapse, and that collapse could only be halted—at most—by nonlinear boun... [Phys. Rev. D 89, 041502] Published Mon Feb 24, 2014
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  • 10
    Publikationsdatum: 2014-02-25
    Beschreibung: Author(s): Raissa F. P. Mendes, George E. A. Matsas, and Daniel A. T. Vanzella General-relativistic stable spacetimes can be made unstable under the presence of certain nonminimally coupled free scalar fields. In this paper, we analyze the evolution of linear scalar-field perturbations in spherically symmetric spacetimes and compare the classical stability analysis with a rece... [Phys. Rev. D 89, 047503] Published Mon Feb 24, 2014
    Schlagwort(e): General relativity, gravitation
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  • 11
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    American Physical Society (APS)
    Publikationsdatum: 2014-04-01
    Beschreibung: Author(s): Sourav Bhattacharya and Hideki Maeda It is shown that, under the separability assumption for the metric, the slow-rotation approximation for the Bocharova-Bronnikov-Melnikov-Bekenstein black hole in general relativity with a conformally coupled scalar field does not work outside the event horizon. Suggestions indicated by our present a... [Phys. Rev. D 89, 087501] Published Mon Mar 31, 2014
    Schlagwort(e): General relativity, gravitation
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  • 12
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    American Physical Society (APS)
    Publikationsdatum: 2014-04-03
    Beschreibung: Author(s): Ted Jacobson We show that Hořava gravity can be obtained from Einstein-aether theory in the limit that the twist coupling constant goes to infinity, while holding fixed the expansion, shear and acceleration couplings. This limit helps to clarify the relation between the two theories, and allows Hořava results to... [Phys. Rev. D 89, 081501] Published Wed Apr 02, 2014
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  • 13
    Publikationsdatum: 2014-04-04
    Beschreibung: Author(s): Eugeny Babichev and Alessandro Fabbri We consider the analytic solutions of massive (bi)gravity which can be written in a simple form using advanced Eddington-Finkelstein coordinates. We analyze the stability of these solutions against radial perturbations. First we recover the previously obtained result on the instability of the bidiag... [Phys. Rev. D 89, 081502] Published Thu Apr 03, 2014
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  • 14
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    American Physical Society (APS)
    Publikationsdatum: 2014-08-30
    Beschreibung: Author(s): Alexander A. H. Graham and Rahul Jha It has been well known since the 1970s that stationary black holes do not generically support scalar hair. Most of the no-hair theorems which support this depend crucially upon the assumption that the scalar field has no time dependence. Here we fill in this omission by ruling out the existence of s... [Phys. Rev. D 90, 041501] Published Fri Aug 29, 2014
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  • 15
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    American Physical Society (APS)
    Publikationsdatum: 2014-10-21
    Beschreibung: Author(s): Xian Gao A general framework for effective theories propagating two tensor and one scalar degrees of freedom is investigated. Geometrically, it describes dynamical foliation of spacelike hypersurfaces coupled to a general background, in which the scalar mode encodes the fluctuation of the hypersurfaces. With... [Phys. Rev. D 90, 081501] Published Mon Oct 20, 2014
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  • 16
    Publikationsdatum: 2014-08-29
    Beschreibung: Author(s): Kenta Kiuchi, Koutarou Kyutoku, Yuichiro Sekiguchi, Masaru Shibata, and Tomohide Wada We perform high-resolution magnetohydrodynamics simulations of binary neutron star mergers in numerical relativity on the Japanese supercomputer K. The neutron stars and merger remnants are covered by a grid spacing of 70 m, which yields the highest-resolution results among those derived so far. By ... [Phys. Rev. D 90, 041502] Published Thu Aug 28, 2014
    Schlagwort(e): General relativity, gravitation
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  • 17
    Publikationsdatum: 2014-11-25
    Beschreibung: Author(s): Riccardo Moriconi, Giovanni Montani, and Salvatore Capozziello We study the asymptotic dynamics of the mixmaster universe, near the cosmological singularity, considering f(R) gravity up to a quadratic correction in the Ricci scalar R. The analysis is performed in the scalar-tensor framework and adopting Misner-Chitré-like variables to describe the mixmaster uni... [Phys. Rev. D 90, 101503] Published Mon Nov 24, 2014
    Schlagwort(e): General relativity, gravitation
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  • 18
    Publikationsdatum: 2014-11-25
    Beschreibung: Author(s): John T. Giblin, Jr. and Eric Thrane The recent claim by BICEP2 of evidence for primordial gravitational waves has focused interest on the potential for early-Universe cosmology using gravitational waves. In addition to cosmic microwave background detectors, efforts are underway to carry out gravitational-wave astronomy with pulsar tim... [Phys. Rev. D 90, 107502] Published Mon Nov 24, 2014
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  • 19
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    American Physical Society (APS)
    Publikationsdatum: 2014-11-05
    Beschreibung: Author(s): J. R. Morris Four-dimensional scalar-tensor theory is considered within two conformal frames, the Jordan frame (JF) and the Einstein frame (EF). The actions for the theory are equivalent and equations of motion can be obtained from each action. It is found that the JF equations of motion, expressed in terms of E... [Phys. Rev. D 90, 107501] Published Tue Nov 04, 2014
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  • 20
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    American Physical Society (APS)
    Publikationsdatum: 2014-11-27
    Beschreibung: Author(s): O. B. Zaslavskii If two particles moving towards a black hole collide near the horizon, their energy in the center-of-mass frame can grow unbounded. This is the so-called Bañados-Silk-West effect. Previously, it was shown that in the 3+1 space-time, this effect has a universal nature. We show that for a wide class o... [Phys. Rev. D 90, 107503] Published Wed Nov 26, 2014
    Schlagwort(e): General relativity, gravitation
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  • 21
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    American Physical Society (APS)
    Publikationsdatum: 2014-12-03
    Beschreibung: Author(s): S. Latifah, A. Sulaksono, and T. Mart By using a simple thermodynamical method, we confirm the finding of Chavanis and Harko that stable Bose-Einstein condensate stars can form. However, by using a thermodynamically consistent boson equation of state, we obtain a less massive Bose-Einstein condensate star compared to the one predicted b... [Phys. Rev. D 90, 127501] Published Tue Dec 02, 2014
    Schlagwort(e): General relativity, gravitation
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  • 22
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    American Physical Society (APS)
    Publikationsdatum: 2014-09-04
    Beschreibung: Author(s): Richard T. Hammond The probability of spin flip of an electron due to a torsional wave is calculated. It is compared to the electromagnetic case, and ways to detect torsion are discussed. [Phys. Rev. D 90, 067501] Published Wed Sep 03, 2014
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  • 23
    Publikationsdatum: 2014-09-05
    Beschreibung: Author(s): I. V. Tanatarov and O. B. Zaslavskii If two particles collide near a black hole, the energy in their center of mass can, under certain conditions, grow unbounded. This is Bañados-Silk-West effect. We show that this effect retains its validity even if some force acts on a particle, provided some reasonable and weak restrictions are impo... [Phys. Rev. D 90, 067502] Published Thu Sep 04, 2014
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  • 24
    Publikationsdatum: 2014-09-06
    Beschreibung: Author(s): Burkhard Kleihaus, Jutta Kunz, and Sindy Mojica We consider rapidly rotating black holes and neutron stars in dilatonic Einstein-Gauss-Bonnet (EGBd) theory and determine their quadrupole moments, which receive a contribution from the dilaton. The quadrupole moment of EGBd black holes can be considerably larger than the Kerr value. For neutron sta... [Phys. Rev. D 90, 061501] Published Fri Sep 05, 2014
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  • 25
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    American Physical Society (APS)
    Publikationsdatum: 2014-09-12
    Beschreibung: Author(s): Amir Ghalee We consider a scalar field with a kinetic term nonminimally coupled to gravity in an anisotropic background. Various potentials for the scalar field are considered. By explicit examples, we show how the anisotropy can change the dynamics of the scalar field compared with the isotropic background. [Phys. Rev. D 90, 067503] Published Thu Sep 11, 2014
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  • 26
    Publikationsdatum: 2014-09-12
    Beschreibung: Author(s): Tolga Birkandan and Mirjam Cvetič We obtained retarded Green’s functions for massless scalar fields in the background of near-extreme, near-horizon rotating charged black hole of five-dimensional minimal gauged supergravity in Phys. Rev. D 84 , 044018 (2011). For general nonextreme black holes, we also derived the radial part of the ... [Phys. Rev. D 90, 067504] Published Thu Sep 11, 2014
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  • 27
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    American Physical Society (APS)
    Publikationsdatum: 2014-12-10
    Beschreibung: Author(s): Matt Visser Event horizons are (generically) not physically observable. In contrast, apparent horizons (and the closely related trapping horizons) are generically physically observable—in the sense that they can be detected by observers working in finite-size regions of spacetime. Consequently event horizons ar... [Phys. Rev. D 90, 127502] Published Fri Dec 05, 2014
    Schlagwort(e): General relativity, gravitation
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  • 28
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    American Physical Society (APS)
    Publikationsdatum: 2014-10-11
    Beschreibung: Author(s): S. Habib Mazharimousavi and M. Halilsoy We reconsider the generalized flare-out conditions in static wormhole throats given by Hochberg and Visser. We show that, due to the presence of matter sources on the throat, these conditions are not applicable to the thin-shell wormholes. [Phys. Rev. D 90, 087501] Published Fri Oct 10, 2014
    Schlagwort(e): General relativity, gravitation
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  • 29
    Publikationsdatum: 2014-09-25
    Beschreibung: Author(s): J. Fernando Barbero G., Tomasz Pawłowski, and Eduardo J. S. Villaseñor We discuss, within the simplified context provided by the polymeric harmonic oscillator, a construction leading to a separable Hilbert space that preserves some of the most important features of the spectrum of the Hamiltonian operator. This construction may be applied to other polymer quantum mecha... [Phys. Rev. D 90, 067505] Published Wed Sep 24, 2014
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  • 30
    Publikationsdatum: 2014-05-23
    Beschreibung: Author(s): K. A. Bronnikov, J. C. Fabris, R. Silveira, and O. B. Zaslavskii We consider Einstein-Maxwell-dilaton gravity with charged dust and interaction of the form P(χ)F μν F μν , where P(χ) is an arbitrary function of the dilaton field χ that can be normal or phantom. For any regular P(χ), static configurations are possible with arbitrary functions g 00 =exp(2γ(x i )) (i=1, 2, ... [Phys. Rev. D 89, 107501] Published Thu May 22, 2014
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  • 31
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    American Physical Society (APS)
    Publikationsdatum: 2014-06-21
    Beschreibung: Author(s): Térence Delsate, Jorge V. Rocha, and Raphael Santarelli We construct exact solutions describing the motion of rotating thin shells in a fully backreacted five-dimensional rotating black hole spacetime. The radial equation of motion follows from the Darmois-Israel junction conditions, where both interior and exterior geometries are taken to be equal angul... [Phys. Rev. D 89, 121501] Published Fri Jun 20, 2014
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  • 32
    Publikationsdatum: 2014-02-21
    Beschreibung: Author(s): Shao-Wen Wei and Yu-Xiao Liu Black hole lensing and gravitational waves are, respectively, closely dependent on the property of the lens and radiation source. In this paper, a universal relation between them is established for a rotating, asymptotically flat black hole acting simultaneously as a lens and a gravitational wave so... [Phys. Rev. D 89, 047502] Published Thu Feb 20, 2014
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  • 33
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    American Physical Society (APS)
    Publikationsdatum: 2014-02-21
    Beschreibung: Author(s): Lawrence M. Krauss and Frank Wilczek While many aspects of general relativity have been tested, and general principles of quantum dynamics demand its quantization, there is no direct evidence for that. It has been argued that development of detectors sensitive to individual gravitons is unlikely, and perhaps impossible. We argue here, ... [Phys. Rev. D 89, 047501] Published Thu Feb 20, 2014
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  • 34
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    American Physical Society (APS)
    Publikationsdatum: 2014-04-10
    Beschreibung: Author(s): Manuel Hohmann We present a static, spherically symmetric, traversable wormhole solution to multimetric gravity which is sustained by only nonexotic matter, i.e., matter which satisfies all energy conditions. The possibility of this solution arises from the fact that under certain conditions the multimetric gravit... [Phys. Rev. D 89, 087503] Published Wed Apr 09, 2014
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  • 35
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    American Physical Society (APS)
    Publikationsdatum: 2014-04-09
    Beschreibung: Author(s): Wenbin Lin and Chunhua Jiang We present an exact and close-form harmonic metric for Kerr-Newman black hole, and demonstrate it is unique in the harmonic coordinates. [Phys. Rev. D 89, 087502] Published Tue Apr 08, 2014
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  • 36
    Publikationsdatum: 2014-04-09
    Beschreibung: Author(s): Thibault Damour, Federico Guercilena, Ian Hinder, Seth Hopper, Alessandro Nagar, and Luciano Rezzolla We probe the gravitational interaction of two black holes in the strong-field regime by computing the scattering angle χ of hyperboliclike, close binary-black-hole encounters as a function of the impact parameter. The fully general-relativistic result from numerical relativity is compared to two ana... [Phys. Rev. D 89, 081503] Published Tue Apr 08, 2014
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  • 37
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    American Physical Society (APS)
    Publikationsdatum: 2014-11-15
    Beschreibung: Author(s): Saoussen Mbarek and M. B. Paranjape We study the possibility of the existence of negative mass bubbles within a de Sitter spacetime background with matter content corresponding to a perfect fluid. It is shown that there exist configurations of the perfect fluid that satisfy everywhere the dominant energy condition, the Einstein equati... [Phys. Rev. D 90, 101502] Published Fri Nov 14, 2014
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  • 38
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    American Physical Society (APS)
    Publikationsdatum: 2014-12-31
    Beschreibung: Author(s): Burkhard Kleihaus and Jutta Kunz We present rotating wormhole solutions in general relativity, which are supported by a phantom scalar field. These solutions evolve from the static Ellis wormhole, when the throat is set into rotation. As the rotational velocity increases, the throat deforms until, at a maximal value of the rotation... [Phys. Rev. D 90, 121503] Published Tue Dec 30, 2014
    Schlagwort(e): General relativity, gravitation
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  • 39
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    American Physical Society (APS)
    Publikationsdatum: 2014-07-12
    Beschreibung: Author(s): Shahar Hod The hydrodynamic vortex, an effective spacetime geometry for propagating sound waves, is studied analytically. In contrast with the familiar Kerr black hole spacetime, the hydrodynamic vortex model is described by an effective acoustic geometry which has no horizons. However, this acoustic spacetime... [Phys. Rev. D 90, 027501] Published Fri Jul 11, 2014
    Schlagwort(e): General relativity, gravitation
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  • 40
    Publikationsdatum: 2014-08-13
    Beschreibung: Author(s): V. S. Manko and H. García-Compeán The Gaussian curvature of the two-surface r=0, t=const is calculated for the Kerr–de Sitter and Kerr–Newman–de Sitter solutions, yielding nonzero analytical expressions for both cases. The results obtained on the one hand exclude the possibility for that surface to be a disk and, on the other hand, ... [Phys. Rev. D 90, 047501] Published Tue Aug 12, 2014
    Schlagwort(e): General relativity, gravitation
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  • 41
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    American Physical Society (APS)
    Publikationsdatum: 2014-08-19
    Beschreibung: Author(s): Cosimo Bambi The construction of a generic parametrization to describe the spacetime geometry around astrophysical black hole candidates is an important step to test the Kerr black hole hypothesis. In the last few years, the Johannsen-Psaltis metric has been the most common framework to study possible deviations... [Phys. Rev. D 90, 047503] Published Mon Aug 18, 2014
    Schlagwort(e): General relativity, gravitation
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  • 42
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    American Physical Society (APS)
    Publikationsdatum: 2014-08-14
    Beschreibung: Author(s): Prasant Samantray and T. Padmanabhan Field theories in black hole spacetimes undergo dimensional reduction near horizon (in the Rindler limit) to two-dimensional conformal field theories. We investigate this enhancement of symmetries in the context of gauge/gravity duality by considering Rindler space as the boundary of anti-de Sitter ... [Phys. Rev. D 90, 047502] Published Wed Aug 13, 2014
    Schlagwort(e): General relativity, gravitation
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  • 43
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    American Physical Society (APS)
    Publikationsdatum: 2014-07-11
    Beschreibung: Author(s): José Barrientos O. and Guillermo F. Rubilar In Phys. Rev. D 84 , 024020 (2011) Harko, Lobo, Nojiri and Odintsov presented a modified theory of gravitation, f(R,T) gravity, where the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and of the trace of the stress-energy tensor. In this Comment we correct the conserv... [Phys. Rev. D 90, 028501] Published Thu Jul 10, 2014
    Schlagwort(e): General relativity, gravitation
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  • 44
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2014-12-18
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉England -- Nature. 2014 Dec 18;516(7531):S72. doi: 10.1038/516S72a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25517243" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry ; China ; Cities ; Periodicals as Topic/statistics & numerical data ; Research/standards/*statistics & numerical data/trends ; Universities/statistics & numerical data
    Print ISSN: 0028-0836
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  • 45
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2014-12-18
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉England -- Nature. 2014 Dec 18;516(7531):S69. doi: 10.1038/516S69a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25517242" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry ; China ; Cities ; Periodicals as Topic/statistics & numerical data ; Physics ; Research/standards/*statistics & numerical data/trends ; Universities/statistics & numerical data
    Print ISSN: 0028-0836
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  • 46
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    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 2014-01-18
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brenner, Sydney -- New York, N.Y. -- Science. 2014 Jan 17;343(6168):262. doi: 10.1126/science.1249912.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore, 138673.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24436413" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Chemistry ; England ; History, 20th Century ; History, 21st Century ; Molecular Biology/*history ; *Nobel Prize ; Sequence Analysis, DNA/*history/methods
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 47
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    American Physical Society (APS)
    Publikationsdatum: 2014-06-26
    Beschreibung: Author(s): L. Herrera, A. Di Prisco, and J. Ospino We study the general properties of axially symmetric dissipative configurations under the shear-free condition. The link between the magnetic part of the Weyl tensor and the vorticity is clearly exhibited, as well as the role of the dissipative fluxes. As a particular case, we examine the geodesic f... [Phys. Rev. D 89, 127502] Published Wed Jun 25, 2014
    Schlagwort(e): General relativity, gravitation
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  • 48
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    American Physical Society (APS)
    Publikationsdatum: 2014-05-09
    Beschreibung: Author(s): Idan Talshir We prove that there are energetically stable bimetric theories. These theories satisfy a positive energy theorem. We construct a model example. [Phys. Rev. D 89, 101501] Published Thu May 08, 2014
    Schlagwort(e): General relativity, gravitation
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  • 49
    Publikationsdatum: 2014-03-06
    Beschreibung: Author(s): Yi Pan, Alessandra Buonanno, Andrea Taracchini, Michael Boyle, Lawrence E. Kidder, Abdul H. Mroué, Harald P. Pfeiffer, Mark A. Scheel, Béla Szilágyi, and Anil Zenginoglu The detection of gravitational waves and the extraction of physical information from them requires the prediction of accurate waveforms to be used in template banks. For that purpose, the accuracy of effective-one-body (EOB) waveforms has been improved over the last years by calibrating them to nume... [Phys. Rev. D 89, 061501] Published Wed Mar 05, 2014
    Schlagwort(e): General relativity, gravitation
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  • 50
    Publikationsdatum: 2014-07-29
    Beschreibung: Author(s): Bruno F. Rizzuti, Everton M. C. Abreu, and Péricles V. Alves The description of the Zitterbewegung at a classical level indicates possible predictions of the electron quantum properties even before quantization: this quivering motion is restricted to a plane, which leads us to only two possible orientations of the corresponding angular momentum, even in the a... [Phys. Rev. D 90, 027502] Published Thu Jul 24, 2014
    Schlagwort(e): General relativity, gravitation
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  • 51
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    American Physical Society (APS)
    Publikationsdatum: 2014-07-30
    Beschreibung: Author(s): Jai-chan Hwang, Hyerim Noh, and Chan-Gyung Park Einstein’s gravity has the exact Newtonian limit as we take the infinite-speed-of-light limit in the zero-shear gauge and the uniform-expansion gauge. Although lacking proper Newtonian gravitational potential, here we show that Newtonian hydrodynamics for density and velocity is also recovered in th... [Phys. Rev. D 90, 027503] Published Tue Jul 29, 2014
    Schlagwort(e): General relativity, gravitation
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  • 52
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    American Physical Society (APS)
    Publikationsdatum: 2014-02-04
    Beschreibung: Author(s): Alexander J. Silenko and Oleg V. Teryaev We consider the dynamics of Dirac particles moving in the curved spaces with one coordinate subjected to compactification and thus interpolating smoothly between three- and two-dimensional spaces. We use the model of compactification, which allows us to perform the exact Foldy-Wouthuysen transformat... [Phys. Rev. D 89, 041501] Published Mon Feb 03, 2014
    Schlagwort(e): General relativity, gravitation
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  • 53
    Publikationsdatum: 2014-02-07
    Beschreibung: Author(s): J. L. Blázquez-Salcedo, L. M. González-Romero, and F. Navarro-Lérida In this paper, we analyze the quasinormal mode spectrum of realistic neutron stars by studying the polar modes. In particular, we calculate the fundamental mode (f mode), the fundamental pressure mode (p mode), and the fundamental curvature mode (wI mode) for 15 different equations of state satisfyi... [Phys. Rev. D 89, 044006] Published Thu Feb 06, 2014
    Schlagwort(e): General relativity, gravitation
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  • 54
    Publikationsdatum: 2014-02-25
    Beschreibung: Author(s): T. C. Adorno, D. M. Gitman, and A. E. Shabad It is demonstrated, owing to the nonlinearity of QED, that a static charge placed in a strong magnetic field B is a magnetic dipole (besides remaining an electric monopole, as well). Its magnetic moment grows linearly with B as long as the latter remains smaller than the characteristic value of 1.2×... [Phys. Rev. D 89, 047504] Published Mon Feb 24, 2014
    Schlagwort(e): General relativity, gravitation
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  • 55
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    American Physical Society (APS)
    Publikationsdatum: 2014-02-26
    Beschreibung: Author(s): Máximo Bañados and Diego Cohen We consider gravity coupled to a second metric in the strong coupling limit, where the second kinetic term is absent. This system belongs to the recently discussed class of models of “gravity with auxiliary fields” by Pani et al. We prove that, in vacuum, these theories are always equivalent to gene... [Phys. Rev. D 89, 047505] Published Tue Feb 25, 2014
    Schlagwort(e): General relativity, gravitation
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  • 56
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    American Physical Society (APS)
    Publikationsdatum: 2014-12-24
    Beschreibung: Author(s): Athanasios Chatzistavrakidis It is shown that a matrix model with SO(d,d) global symmetry is derived from a generalized Yang-Mills theory on the standard Courant algebroid. This model keeps all the positive features of the well-studied type IIB matrix model, and it has many additional welcome properties. We show that it not onl... [Phys. Rev. D 90, 121502] Published Tue Dec 23, 2014
    Schlagwort(e): General relativity, gravitation
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  • 57
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    In:  CASI
    Publikationsdatum: 2018-06-11
    Beschreibung: The Human Exploration Science Office supports human spaceflight, conducts research, and develops technology in the areas of space orbital debris, hypervelocity impact technology, image science and analysis, remote sensing, imagery integration, and human and robotic exploration science. NASA's Orbital Debris Program Office (ODPO) resides in the Human Exploration Science Office. ODPO provides leadership in orbital debris research and the development of national and international space policy on orbital debris. The office is recognized internationally for its measurement and modeling of the debris environment. It takes the lead in developing technical consensus across U.S. agencies and other space agencies on debris mitigation measures to protect users of the orbital environment. The Hypervelocity Impact Technology (HVIT) project evaluates the risks to spacecraft posed by micrometeoroid and orbital debris (MMOD). HVIT facilities at JSC and White Sands Test Facility (WSTF) use light gas guns, diagnostic tools, and high-speed imagery to quantify the response of spacecraft materials to MMOD impacts. Impact tests, with debris environment data provided by ODPO, are used by HVIT to predict risks to NASA and commercial spacecraft. HVIT directly serves NASA crew safety with MMOD risk assessments for each crewed mission and research into advanced shielding design for future missions. The Image Science and Analysis Group (ISAG) supports the International Space Station (ISS) and commercial spaceflight through the design of imagery acquisition schemes (ground- and vehicle-based) and imagery analyses for vehicle performance assessments and mission anomaly resolution. ISAG assists the Multi-Purpose Crew Vehicle (MPCV) Program in the development of camera systems for the Orion spacecraft that will serve as data sources for flight test objectives that lead to crewed missions. The multi-center Imagery Integration Team is led by the Human Exploration Science Office and provides expertise in the application of engineering imagery to spaceflight. The team links NASA programs and private industry with imagery capabilities developed and honed through decades of human spaceflight, including imagery integration, imaging assets, imagery data management, and photogrammetric analysis. The team is currently supporting several NASA programs, including commercial demonstration missions. The Earth Science and Remote Sensing Team is responsible for integrating the scientific use of Earth-observation assets onboard the ISS, which consist of externally mounted sensors and crew photography capabilities. This team facilitates collaboration on remote sensing and participates in research with academic organizations and other Government agencies, not only in conjunction with ISS science, but also for planetary exploration and regional environmental/geological studies. Human exploration science focuses on science strategies for future human exploration missions to the Moon, Mars, asteroids, and beyond. This function provides communication and coordination between the science community and mission planners. ARES scientists support the operation of robotic missions (i.e., Mars Exploration Rovers and the Mars Science Laboratory), contribute to the interpretation of returned mission data, and translate robotic mission technologies and techniques to human spaceflight.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 51-52; JSC-CN-30442
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  • 58
    Publikationsdatum: 2018-06-11
    Beschreibung: The GeoLab glovebox was, until November 2012, fully integrated into NASA's Deep Space Habitat (DSH) Analog Testbed. The conceptual design for GeoLab came from several sources, including current research instruments (Microgravity Science Glovebox) used on the International Space Station, existing Astromaterials Curation Laboratory hardware and clean room procedures, and mission scenarios developed for earlier programs. GeoLab allowed NASA scientists to test science operations related to contained sample examination during simulated exploration missions. The team demonstrated science operations that enhance theThe GeoLab glovebox was, until November 2012, fully integrated into NASA's Deep Space Habitat (DSH) Analog Testbed. The conceptual design for GeoLab came from several sources, including current research instruments (Microgravity Science Glovebox) used on the International Space Station, existing Astromaterials Curation Laboratory hardware and clean room procedures, and mission scenarios developed for earlier programs. GeoLab allowed NASA scientists to test science operations related to contained sample examination during simulated exploration missions. The team demonstrated science operations that enhance the early scientific returns from future missions and ensure that the best samples are selected for Earth return. The facility was also designed to foster the development of instrument technology. Since 2009, when GeoLab design and construction began, the GeoLab team [a group of scientists from the Astromaterials Acquisition and Curation Office within the Astromaterials Research and Exploration Science (ARES) Directorate at JSC] has progressively developed and reconfigured the GeoLab hardware and software interfaces and developed test objectives, which were to 1) determine requirements and strategies for sample handling and prioritization for geological operations on other planetary surfaces, 2) assess the scientific contribution of selective in-situ sample characterization for mission planning, operations, and sample prioritization, 3) evaluate analytical instruments and tools for providing efficient and meaningful data in advance of sample return and 4) identify science operations that leverage human presence with robotic tools. In the first year of tests (2010), GeoLab examined basic glovebox operations performed by one and two crewmembers and science operations performed by a remote science team. The 2010 tests also examined the efficacy of basic sample characterization [descriptions, microscopic imagery, X-ray fluorescence (XRF) analyses] and feedback to the science team. In year 2 (2011), the GeoLab team tested enhanced software and interfaces for the crew and science team (including Web-based and mobile device displays) and demonstrated laboratory configurability with a new diagnostic instrument (the Multispectral Microscopic Imager from the JPL and Arizona State University). In year 3 (2012), the GeoLab team installed and tested a robotic sample manipulator and evaluated robotic-human interfaces for science operations.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 40-44; JSC-CN-30442
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  • 59
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    In:  CASI
    Publikationsdatum: 2018-06-11
    Beschreibung: No abstract available
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 30-32; JSC-CN-30442
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  • 60
    Publikationsdatum: 2018-06-11
    Beschreibung: No abstract available
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 26-27; JSC-CN-30442
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  • 61
    Publikationsdatum: 2018-06-11
    Beschreibung: No abstract available
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 20-21; JSC-CN-30442
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  • 62
    Publikationsdatum: 2018-06-11
    Beschreibung: Our work has elucidated a new analog for the formation of giant polygons on Mars, involving fluid expulsion in a subaqueous environment. That work is based on three-dimensional (3D) seismic data on Earth that illustrate the mud volcanoes and giant polygons that result from sediment compaction in offshore settings. The description of this process has been published in the journal Icarus, where it will be part of a special volume on Martian analogs. These ideas have been carried further to suggest that giant polygons in the Martian lowlands may be the signature of an ancient ocean and, as such, could mark a region of enhanced habitability. A paper describing this hypothesis has been published in the journal Astrobiology.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 12-14; JSC-CN-30442
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  • 63
    Publikationsdatum: 2018-06-11
    Beschreibung: As of 2013, about 60 meteorites from the planet Mars have been found and are being studied. Each time a new Martian meteorite is found, a wealth of new information comes forward about the red planet. The most abundant type of Martian meteorite is a shergottite; its lithologies are broadly similar to those of Earth basalts and gabbros; i.e., crustal igneous rocks. The entire suite of shergottites is characterized by a range of trace element, isotopic ratio, and oxygen fugacity values that mainly reflect compositional variations of the Martian mantle from which these magmas came. A newly found shergottite, NWA 5298, was the focus of a study performed by scientists within the Astromaterials Research and Exploration Science (ARES) Directorate at the Johnson Space Center (JSC) in 2012. This sample was found in Morocco in 2008. Major element analyses were performed in the electron microprobe (EMP) laboratory of ARES at JSC, while the trace elements were measured at the University of Houston by laser inductively coupled plasma mass spectrometry (ICPMS). A detailed analysis of this stone revealed that this meteorite is a crystallized magma that comes from the enriched end of the shergottite spectrum; i.e., trace element enriched and oxidized. Its oxidation comes in part from its mantle source and from oxidation during the magma ascent. It represents a pristine magma that did not mix with any other magma or see crystal accumulation or crustal contamination on its way up to the Martian surface. NWA 5298 is therefore a direct, albeit evolved, melt from the Martian mantle and, for its lithology (basaltic shergottite), it represents the oxidized end of the shergottite suite. It is thus a unique sample that has provided an end-member composition for Martian magmas.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 8-9; JSC-CN-30442
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  • 64
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    In:  CASI
    Publikationsdatum: 2018-06-11
    Beschreibung: The Astromaterials Acquisition and Curation Office has the unique responsibility to curate NASA's extraterrestrial samples - from past and forthcoming missions - into the indefinite future. Currently, curation includes documentation, preservation, physical security, preparation, and distribution of samples from the Moon, asteroids, comets, the solar wind, and the planet Mars. Each of these sample sets has a unique history and comes from a unique environment. The curation laboratories and procedures developed over 40 years have proven both necessary and sufficient to serve the evolving needs of a worldwide research community. A new generation of sample return missions to destinations across the solar system is being planned and proposed. The curators are developing the tools and techniques to meet the challenges of these new samples. Extraterrestrial samples pose unique curation requirements. These samples were formed and exist under conditions strikingly different from those on the Earth's surface. Terrestrial contamination would destroy much of the scientific significance of extraterrestrial materials. To preserve the research value of these precious samples, contamination must be minimized, understood, and documented. In addition, the samples must be preserved - as far as possible - from physical and chemical alteration. The elaborate curation facilities at JSC were designed and constructed, and have been operated for many years, to keep sample contamination and alteration to a minimum. Currently, JSC curates seven collections of extraterrestrial samples: (a)) Lunar rocks and soils collected by the Apollo astronauts, (b) Meteorites collected on dedicated expeditions to Antarctica, (c) Cosmic dust collected by high-altitude NASA aircraft,t (d) Solar wind atoms collected by the Genesis spacecraft, (e) Comet particles collected by the Stardust spacecraft, (f) Interstellar dust particles collected by the Stardust spacecraft, and (g) Asteroid soil particles collected by the Japan Aerospace Exploration Agency (JAXA) Hayabusa spacecraft Each of these sample sets has a unique history and comes from a unique environment. We have developed specialized laboratories and practices over many years to preserve and protect the samples, not only for current research but for studies that may be carried out in the indefinite future.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 35-36; JSC-CN-30442
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  • 65
    Publikationsdatum: 2018-06-11
    Beschreibung: No abstract available
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 33-34; JSC-CN-30442
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  • 66
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    In:  CASI
    Publikationsdatum: 2018-06-11
    Beschreibung: No abstract available
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 27-30; JSC-CN-30442
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  • 67
    Publikationsdatum: 2018-06-11
    Beschreibung: While comets are perhaps best known for their ability to put on spectacular celestial light shows, they are much more than that. Composed of an assortment of frozen gases mixed with a collection of dust and minerals, comets are considered to be very primitive bodies and, as such, they are thought to hold key information about the earliest chapters in the history of the solar system. (The dust and mineral grains are usually called the "refractory" component, indicating that they can survive much higher temperatures than the ices.) It has long been thought, and spacecraft photography has confirmed, that comets suffer the effects of impacts along with every other solar system body. Comets spend most of their lifetimes in the Kuiper Belt, a region of the solar system between 30 and 50 times the average distance of the Earth from the Sun, or the Oort Cloud, which extends to approximately 1 light year from the Sun. Those distances are so far from the Sun that water ice is the equivalent of rock, melting or vaporizing only through the action of strong, impact-generated shock waves.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 10-12; JSC-CN-30442
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  • 68
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    In:  CASI
    Publikationsdatum: 2018-06-11
    Beschreibung: The 2012 Moon and Mars Analog Mission Activities (MMAMA) scientific investigations were completed on Mauna Kea volcano in Hawaii in July 2012. The investigations were conducted on the southeast flank of the Mauna Kea volcano at an elevation of approximately 11,500 ft. This area is known as "Apollo Valley" and is in an adjacent valley to the Very Large Baseline Array dish antenna.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 91-94; JSC-CN-30442
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  • 69
    Publikationsdatum: 2018-06-11
    Beschreibung: No abstract available
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 80-86; JSC-CN-30442
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  • 70
    Publikationsdatum: 2018-06-11
    Beschreibung: The purpose of NASA Extreme Environment Mission Operations (NEEMO) mission 16 in 2012 was to evaluate and compare the performance of a defined series of representative near-Earth asteroid (NEA) extravehicular activity (EVA) tasks under different conditions and combinations of work systems, constraints, and assumptions considered for future human NEA exploration missions. NEEMO 16 followed NASA's 2011 Desert Research and Technology Studies (D-RATS), the primary focus of which was understanding the implications of communication latency, crew size, and work system combinations with respect to scientific data quality, data management, crew workload, and crew/mission control interactions. The 1-g environment precluded meaningful evaluation of NEA EVA translation, worksite stabilization, sampling, or instrument deployment techniques. Thus, NEEMO missions were designed to provide an opportunity to perform a preliminary evaluation of these important factors for each of the conditions being considered. NEEMO 15 also took place in 2011 and provided a first look at many of the factors, but the mission was cut short due to a hurricane threat before all objectives were completed. ARES Directorate (KX) personnel consulted with JSC engineers to ensure that high-fidelity planetary science protocols were incorporated into NEEMO mission architectures. ARES has been collaborating with NEEMO mission planners since NEEMO 9 in 2006, successively building upon previous developments to refine science operations concepts within engineering constraints; it is expected to continue the collaboration as NASA's human exploration mission plans evolve.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARES Biennial Report 2012 Final; 88-91; JSC-CN-30442
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  • 71
    Publikationsdatum: 2019-07-19
    Beschreibung: We present the analysis of Cassini spectral data from spectral mapping of Saturnian icy moons Dione and Rhea, to investigate possible effects of impact crater formation on the relative abundances of crystalline and amorphous water ice in the moons' ice crusts. Both moons display morphologically young ray craters as well as older craters. Possible changes in ice properties due to crater formation are conjectured to be more visible in younger craters, and as such Rhea's well imaged ray crater Inktomi is analysed, as are older craters for comparison. We used data from Cassini's Visual and Infrared Mapping Spectrometer (VIMS). For each pixel in the VIMS maps, spectral data were extracted in the near-infrared range (1.75 micrometers less than lambda less than 2.45 micrometers). Analysis was begun by fitting a single Gaussian to the peak in absorption at 2.0 micrometers, which was then subtracted from the data, leaving residuals with a minimum on either side of the original 2.0-micrometers band. The spectra of the individual spatial pixels were then clustered by the differences between these minima, which are sensitive to changes in both ice grain size and crystallinity. This yielded preliminary maps which approximated the physical characteristics of the landscape and were used to identify candidates for further analysis. Spectra were then clustered by the properties of the 1.5-micrometers band, to divide the map into regions based on inferred grain size. For each region, the predicted differences in minima from the Gaussian residuals, over a range of crystallinities, were calculated based on the found grain sizes. This model was used to find the crystallinity of each pixel via grain size and characteristics of the residual function. Preliminary results show a greater degree of crystallization of young crater interiors, particularly in Rhea's ray crater Inktomi, where ice showed crystalline ice abundances between 33 percent and 61 percent. These patterns in ice crystallization are possibly attributable to increased heat generated during crater formation.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARC-E-DAA-TN18021 , Annual Meeting, American Astronomical Society, Div. for Planetary Science; Nov 09, 2014 - Nov 14, 2014; Tucson,AZ; United States
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  • 72
    Publikationsdatum: 2019-07-19
    Beschreibung: Isotopic dating is an essential tool to establish an absolute chronology for geological events, including crystallization history, magmatic evolution, and alteration events. The capability for in situ geochronology will open up the ability for geochronology to be accomplished as part of lander or rover complement, on multiple samples rather than just those returned. An in situ geochronology package can also complement sample return missions by identifying the most interesting rocks to cache or return to Earth. The K-Ar Laser Experiment (KArLE) brings together a novel combination of several flight-proven components to provide precise measurements of potassium (K) and argon (Ar) that will enable accurate isochron dating of planetary rocks. KArLE will ablate a rock sample, measure the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measure the liberated Ar using mass spectrometry (MS), and relate the two by measuring the volume of the ablated pit by optical imaging. Our work indicates that the KArLE instrument is capable of determining the age of planetary samples with sufficient accuracy to address a wide range of geochronology problems in planetary science. Additional benefits derive from the fact that each KArLE component achieves analyses useful for most planetary surface missions.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: M15-4143 , International Workshop on Instrumentation for Planetary Missions (IPM-2014); Nov 04, 2014 - Nov 07, 2014; Greenbelt, MD; United States
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  • 73
    Publikationsdatum: 2019-07-19
    Beschreibung: Plans to send humans to Mars are in work and the launch system is being built. Are we ready? Robotic missions have successfully demonstrated transportation, entry, landing and surface operations but for human missions there are significant, potentially show-stopping issues. These issues, called Strategic Knowledge Gaps (SKGs) are the unanswered questions concerning long-duration exploration beyond low-earth-orbit. The gaps represent a risk of loss of life or mission and because they require extended exposure to the weightless environment outside earth's protective geo-magnetic field they cannot be resolved on the earth or on the International Space Station (ISS). Placing a laboratory at the relatively close and stable lunar Distant Retrograde Orbit (DRO) provides an accessible location with the requisite environmental conditions for conducting SKG research and testing mitigation solutions. Configurations comprised of multiple 3 meter and 4.3 meter diameter modules have been studied but the most attractive solution uses elements of the human Mars launch vehicle or Space Launch System (SLS) for a Mars proving ground laboratory. A shortened version of an SLS hydrogen propellant tank creates a Skylab-like pressure vessel that flies fully outfitted on a single launch. This not only offers significant savings by incorporating SLS pressure vessel development costs but avoids the expensive ISS approach using many launches with substantial on-orbit assembly before becoming operational. One of the most challenging SKGs is crew radiation protection; this is why SKG laboratory research is combined with Mars transit Habitat systems development. Fundamentally, the two cannot be divorced because using the habitat systems for protection requires actual hardware geometry and material properties intended to contribute to shielding effectiveness. The SKGs are difficult problems, solutions are not obvious, and require integrated, iterative, and multi-disciplinary development. A lunar DRO lab built from the launch system elements enables an early and representative transit habitat test bed necessary for closing gaps before sending humans on a 1000 day Mars mission.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: M15-4351 , AIAA Space 2015; Aug 31, 2015 - Sep 02, 2015; Pasadena, CA; United States
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  • 74
    Publikationsdatum: 2019-07-19
    Beschreibung: We will summarize the in situ measurements of atmospheric composition and the isotopic ratios of D/H in water, C-13/C-12, O-18/O-16, O-17 / O-16, and C-13 O-18 / C-12 O-16 in carbon dioxide, and Ar-38 / Ar-36, Kr-x / Kr-84, and N-15 / N-14 made in the martian atmosphere at Gale Crater from the Curiosity Rover using the Sample Analysis at Mars (SAM)'s Quadrupole Mass Spectrometer (QMS) and Tunable Laser Spectrometer (TLS). With data over 700 sols since the Curiosity landing, we will discuss evidence and implications for changes on seasonal and other timescales. We will also present results for continued methane and methane enrichment experiments over this time period. Comparison between our measurements in the modern atmosphere and those of martian meteorites like ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established approximately 4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-32507 , AGU Fall Meeting; Dec 14, 2014 - Dec 19, 2014; San Francisco, CA; United States
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  • 75
    Publikationsdatum: 2019-07-19
    Beschreibung: One of the key objectives of the Mars Science Laboratory rover and the Sample Analysis at Mars (SAM) instrument suite is to determine the inventory of organic and inorganic volatiles in the atmosphere and surface regolith and rocks to help assess the habitability potential of Gale Crater. The SAM instrument on the Curiosity rover can detect volatile organic compounds thermally evolved from solid samples using a combination of evolved gas analysis (EGA) and gas chromatography mass spectrometry (GCMS) (Mahaffy et al. 2012). The first solid samples analyzed by SAM, a scoop of windblown dust and sand at Rocknest, revealed several chloromethanes and a C4-chlorinated hydrocarbon derived primarily from reactions between a martian oxychlorine phase (e.g. perchlorate) and terrestrial carbon from N-methyl-N-(tertbutyldimethylsilyl)- trifluoroacetamide (MTBSTFA) vapor present in the SAM instrument background (Glavin et al. 2013). After the analyses at Rocknest, Curiosity traveled to Yellowknife Bay and drilled two separate holes in a fluvio-lacustrine sediment (the Sheepbed unit) designated John Klein and Cumberland. Analyses of the drilled materials by both SAM and the CheMin X-Ray Diffraction instrument revealed a mudstone consisting of ~20 wt% smectite clays (Ming et al. 2013; Vaniman et al. 2013), which on Earth are known to aid the concentration and preservation of organic matter. Oxychlorine compounds were also detected in the Sheepbed mudstone during pyrolysis; however, in contrast to Rocknest, much higher levels of chloromethanes were released from the Sheepbed materials, suggesting an additional, possibly martian source of organic carbon (Ming et al. 2013). In addition, elevated abundances of chlorobenzene and a more diverse suite of chlorinated alkanes including dichloropropane and dichlorobutane detected in Cumberland compared to Rocknest suggest that martian or meteoritic organic carbon sources may be preserved in the mudstone (Freissinet et al. 2013). Chloromethane and dichloromethane were also identified after thermal volatilization of the surface soils by the GCMS instruments at the Viking landing sites, although no other chlorinated hydrocarbons were reported (Biemann et al. 1977). Here we focus on the origin of the chlorinated hydrocarbons detected in the Sheepbed mudstone by SAM and the implications for the preservation of organic matter in near-surface materials on Mars.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: GSFC-E-DAA-TN13374 , Joint Conference of the International Astrobiology Society and Bioastronomy; Jul 06, 2014 - Jul 11, 2014; Nara; Japan|Origins 2014; Jul 06, 2014 - Jul 11, 2014; Nara; Japan
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  • 76
    Publikationsdatum: 2019-07-19
    Beschreibung: The decades-or-longer stability of the narrow F Ring core in a sea of orbital chaos appears to be due to an unusual combination of traditional corotation resonance and a novel kind of "antiresonance". At a series of specific locations in the F Ring region, apse precession between synodic encounters with Prometheus allows semimajor axis perturbations to promptly cancel before significant orbital period changes can occur. This cancellation fails for particles that encounter Prometheus when it is near its apoapse, especially during periods of antialignment of its apse with that of the F Ring. At these times, the strength of the semimajor axis perturbation is large (tens of km) and highly nonsinusoidal in encounter longitude, making it impossible to cancel promptly on a subsequent encounter and leading to chaotic orbital diffusion. Only particles that consistently encounter Prometheus away from its apoapse can use antiresonance to maintain stable orbits, implying that the true mean motion nF of the stable core must be defined by a corotational resonance of the form nF = nP(-kappa)P/m, where (nP, kappaP) are Prometheus' mean motion and epicycle frequency. To test this hypothesis we used the fact that Cassini RSS occultations only sporadically detect a "massive" F Ring core, composed of several-cm-and-larger particles. We regressed the inertial longitudes of 24 Cassini RSS (and VGR) detections and 43 nondetections to a common epoch, using a comb of candidate nP, and then folded them modulo the anticipated m-number of the corotational resonance (Prometheus m = 110 outer CER), to see if clustering appears. We find the "true F Ring core" is actually arranged in a series of short longitudinal arcs separated by nearly empty longitudes, orbiting at a well determined semimajor axis of 140222.4 km (from 2005-2012 at least). Small particles seen by imaging and stellar occultations spread quickly in azimuth and obscure this clumpy structure. Small chaotic variations in the mean motion and/or apse longitude of Prometheus quickly become manifest in the F Ring core, and we suggest that the core must adapt to these changes for the F Ring to maintain stability over timescales of decades and longer
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: ARC-E-DAA-TN17919 , Meeting of the AAS Division for Planetary Sciences; Nov 09, 2014 - Nov 14, 2014; Tucson, AZ; United States
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  • 77
    Publikationsdatum: 2019-07-19
    Beschreibung: NASA is examining two options for the Asteroid Redirect Mission (ARM), which will return asteroid material to a Lunar Distant Retrograde Orbit (LDRO) using a robotic solar-electric-propulsion spacecraft, called the Asteroid Redirect Vehicle (ARV). Once the ARV places the asteroid material into the LDRO, a piloted mission will rendezvous and dock with the ARV. After docking, astronauts will conduct two extravehicular activities (EVAs) to inspect and sample the asteroid material before returning to Earth. One option involves capturing an entire small (approximately 4-10 m diameter) near-Earth asteroid (NEA) inside a large inflatable bag. However, NASA is examining another option that entails retrieving a boulder (approximately 1-5 m) via robotic manipulators from the surface of a larger (approximately 100+ m) pre-characterized NEA. This option can leverage robotic mission data to help ensure success by targeting previously (or soon to be) well-characterized NEAs. For example, the data from the Hayabusa mission has been utilized to develop detailed mission designs that assess options and risks associated with proximity and surface operations. Hayabusa's target NEA, Itokawa, has been identified as a valid target and is known to possess hundreds of appropriately sized boulders on its surface. Further robotic characterization of additional NEAs (e.g., Bennu and 1999 JU3) by NASA's OSIRIS REx and JAXA's Hayabusa 2 missions is planned to begin in 2018. The boulder option is an extremely large samplereturn mission with the prospect of bringing back many tons of wellcharacterized asteroid material to the EarthMoon system. The candidate boulder from the target NEA can be selected based on inputs from the worldwide science community, ensuring that the most scientifically interesting boulder be returned for subsequent sampling. This boulder option for NASA's ARM can leverage knowledge of previously characterized NEAs from prior robotic missions, which provides more certainty of the target NEA's physical characteristics and reduces mission risk. This increases the return on investment for NASA's future activities with respect to science, human exploration, resource utilization, and planetary defense
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-32111 , Annual Meeting of the Division for Planetary Sciences; Nov 09, 2014 - Nov 14, 2014; Tuscon, AZ; United States
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  • 78
    Publikationsdatum: 2019-07-19
    Beschreibung: Based on petrology, mineralogy, and bulk composition, the new NWA 8159 martian meteorite is distinct from all known samples from Mars. In particular, the augite compositional trends are unique, but most similar to those of nakhite intercumulus. Whether NWA 8159 represents a new lithology or is related to a known meteorite group remains to be determined. Sr and Nd isotopic analyses will allow comparison of source characteristics with SNC and other new ungrouped meteorites (e.g., NWA 7635). Here we report initial Rb-Sr and Sm-Nd isotopic results for NWA 8159 with the objective to determine its formation age and to potentially identify similarities and potential source affinities with other martian rocks.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-31532 , Annual Meeting of the Meteoritical Society; Sep 08, 2014 - Sep 13, 2014; Casablanca; Morocco
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  • 79
    Publikationsdatum: 2019-07-19
    Beschreibung: The rates of space weathering processes are poorly constrained for asteroid surfaces, with recent estimates ranging over 5 orders of magnitude. The return of the first surface samples from a space-weathered asteroid by the Hayabusa mission and their laboratory analysis provides "ground truth" to anchor the timescales for space weathering. We determine the rates of space weathering on Itokawa by measuring solar flare track densities and the widths of solar wind damaged rims on grains. These measurements are made possible through novel focused ion beam (FIB) sample preparation methods.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-32113 , HAYABUSA 2014: Symposium on Solar System Materials; Dec 04, 2014 - Dec 05, 2014; Kanagawa; Japan
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  • 80
    Publikationsdatum: 2019-07-19
    Beschreibung: The Diviner Lunar Radiometer, onboard NASA's Lunar Reconnaissance Orbiter, has produced the first global, high resolution, thermal infrared observations of an airless body. The Moon, which is the most accessible member of this most abundant class of solar system objects, is also the only body for which we have extraterrestrial samples with known spatial context. Here we present the results of a comprehensive study to reproduce an accurate simulated lunar environment, evaluate the most appropriate sample and measurement conditions, collect thermal infrared spectra of a representative suite of Apollo soils, and correlate them with Diviner observations of the lunar surface. We find that analyses of Diviner observations of individual sampling stations and SLE measurements of returned Apollo soils show good agreement, while comparisons to thermal infrared reflectance under terrestrial conditions do not agree well, which underscores the need for SLE measurements and validates the Diviner compositional dataset. Future work includes measurement of additional soils in SLE and cross comparisons with measurements in JPL Simulated Airless Body Emission Laboratory (SABEL).
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-32094 , Annual Meeting of the Lunar Exploration Analysis Group 2014; Oct 22, 2014 - Oct 24, 2014; Laurel, MD; United States
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  • 81
    Publikationsdatum: 2019-07-19
    Beschreibung: One of the fundamental aspects of any astromaterial is its shock history, since this factor elucidates critical historical events, and also because shock metamorphism can alter primary mineralogical and petrographic features, and reset chronologies.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-32091
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  • 82
    Publikationsdatum: 2019-07-19
    Beschreibung: The main goal of the Japanese Aerospace Ex-ploration Agency (JAXA) Hayabusa-2 mission is to visit and return to Earth samples of a C-type asteroid (162173) 1999 JU3 in order to understand the origin and nature of organic materials in the Solar System. Life on Earth shows preference towards the set of organics with particular spatial arrangements, this 'selectivity' is a crucial criterion for life. With only rare exceptions, life 'determines' to use the left- (L-) form over the right- (D-) form of amino acids, resulting in a L-enantiomeric excess (ee). Recent studies have shown that L-ee is found within the alpha-methyl amino acids in meteorites [1, 2], which are amino acids with rare terrestrial occurrence, and thus point towards a plausible abiotic origin for ee. One of the proposed origins of chiral asymmetry of amino acids in meteorites is their formation with the presence of asymmetric catalysts [3]. The catalytic mineral grains acted as a surface at which nebular gases (CO, H2 and NH3) were allowed to condense and react through Fisher Tropsch type (FTT) syntheses to form the organics observed in meteorites [4]. Magnetite is shown to be an effective catalyst of the synthesis of amino acids that are commonly found in meteorites [5]. It has also taken the form as spiral magnetites (a.k.a. 'plaquettes'), which were found in various carbonaceous chondrites (CCs), including C2s Tagish Lake and Esseibi, CI Orgueil, and CR chondrites [e.g., 6, 7, 8]. In addition, L-ee for amino acids are common in the aqueously altered CCs, as opposed to the unaltered CCs [1]. It seems possible that the synthesis of amino acids with chiral preferences is correlated to the alteration process experienced by the asteroid parent body, and related to the configuration of spiral magnetite catalysts. Since C-type asteroids are considered to be enriched in organic matter, and the spectral data of 1999 JU3 indicates a certain de-gree of aqueous alteration [9], the Hayabusa-2 mission serves as a perfect chance to attest this argument. In order to understand the distribution of spiral magnetites among different meteorite classes, as well as to investigate their spiral configurations and correlation to molecular asymmetry, we observed polished thin sections of CCs using scanning electron microscope (SEM) imaging. Individual magnetite grains were picked, embedded in epoxy, thin-sectioned using an ultra-microtome, and studied with electron backscatter diffraction (EBSD) in order to reconstruct the crystal orientation along the stack of magnetite disks.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-32090
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  • 83
    Publikationsdatum: 2019-07-19
    Beschreibung: The focus of the present study is the compositional analysis of small-scale surface features within the Rheasil-Aa basin on asteroid Vesta. We are using data acquired by the Visible and InfraRed mapping Spectrometer (VIR) on the Dawn mission. Nominal spatial resolution of the data set considered in this study is 70m/px. The portion of Rheasil-Aa basin below 65degS has a howarditic composition, with the higher concentration of diogenitic versus eucritic material in the region between 45deg and 225degE-lon. However, there are several locations, such as craters Tarpeia and Severina and Parentatio Rupes, with lithologic characteristics different from the surroundings regions. Tarpeia crater has a eucritic patch in the west side of the crater, the bottom part ofthe wall and part of the floor. Severina, located in a region of Mg-rich pyroxene, has some diogenitic units on the walls of the crater. Also the Parentatio Rupes has an ob-AOUS diogenitic unit. These units extend for 10-20km, and their location, especially in the case of the two craters, suggests they formed before the cratering events and also before the Rheasil-Aa impact event. The origin of these units is still unclear; however, their characteristics and locations suggests heterogeneity in the composition of the ancient Vestan crust in this particular location of the surface.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-32077 , American Geophysical Union (AGU) Fall Meeting; Dec 15, 2014 - Dec 19, 2014; San Francisco, CA; United States
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  • 84
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    In:  CASI
    Publikationsdatum: 2019-07-19
    Beschreibung: Some types of meteorites - most irons, stony irons, some achondrites - hail from asteroids that were heated to the point where magmatism occurred within a very few million years of the formation of the earliest solids in the solar system. The largest clan of achondrites, the howardite, eucrite and diogenite (HED) meteorites, represent the crust of their parent asteroid]. Diogenites are cumulate harzburgites and orthopyroxenites from the lower crust whilst eucrites are basalts, diabases and cumulate gabbros from the upper crust. Howardites are impact-engendered breccias mostly of diogenites and eucrites. There remains only one large asteroid with a basaltic crust, 4 Vesta, which is thought to be the source of the HED clan. Differentiation models for Vesta are based on HED compositions. Proto-Vesta consisted of chondritic materials containing Al-26, a potent, short-lived heat source. Inferences from compositional data are that Vesta was melted to high degree (50%) allowing homogenization of the silicate phase and separation of a metallic core. Convection of the silicate magma ocean allowed equilibrium crystallization, forming a harzburgitic mantle. After convective lockup occurred, melt collected between the mantle and the cool thermal boundary layer and underwent fractional crystallization forming an orthopyroxene-rich (diogenite) lower crust. The initial thermal boundary layer of chondritic material was replaced by a mafic upper crust through impact disruption and foundering. The mafic crust thickened over time as additional residual magma intrudes and penetrates the mafic crust forming plutons, dikes, sills and flows of cumulate and basaltic eucrite composition. This magmatic history may have taken only 2-3 Myr. This magma ocean scenario is at odds with a model of heat and magma transport that indicates that small degrees of melt would be rapidly expelled from source regions, precluding development of a magma ocean. Constraints from radiogenic Mg-26 distibutions suggest that the parent asteroid of HEDs was much smaller than Vesta. Thus, first-order questions regarding asteroid differentiation remain.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-30640 , Goldschmidt2014; Jun 08, 2014 - Jun 13, 2014; Sacramento, CA; United States
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  • 85
    Publikationsdatum: 2019-07-19
    Beschreibung: Water ice and other volatiles may be located in the Moon's polar regions, with sufficient quantities for in situ extraction and utilization by future human and robotic missions. Evidence from orbiting spacecraft and the LCROSS impactor suggests the presence of surface and/or nearsurface volatiles, including water ice. These deposits are of interest to human exploration to understand their potential for use by astronauts. Understanding the composition, quantity, distribution, and form of water/H species and other volatiles associated with lunar cold traps is identified as a NASA Strategic Knowledge Gap (SKG) for Human Exploration. These polar volatile deposits could also reveal important information about the delivery of water to the Earth- Moon system, so are of scientific interest. The scientific exploration of the lunar polar regions was one of the key recommendations of the Planetary Science Decadal Survey. In order to address NASA's SKGs, the Advanced Exploration Systems (AES) program selected three lowcost 6-U CubeSat missions for launch as secondary payloads on the first test flight (EM1) of the Space Launch System (SLS) scheduled for 2017. The Lunar Flashlight mission was selected as one of these missions, specifically to address the SKG associated with lunar volatiles. Development of the Lunar Flashlight CubeSat concept leverages JPL's Interplanetary Nano- Spacecraft Pathfinder In Relevant Environment (INSPIRE) mission, MSFC's intimate knowledge of the Space Launch System and EM-1 mission, small business development of solar sail and electric propulsion hardware, and JPL experience with specialized miniature sensors. The goal of Lunar Flashlight is to determine the presence or absence of exposed water ice and its physical state, and map its concentration at the kilometer scale within the permanently shadowed regions of the lunar south pole. After being ejected in cislunar space by SLS, Lunar Flashlight deploys its solar panels and solar sail and maneuvers into a low-energy transfer to lunar orbit. The solar sail and attitude control system work to bring the satellite into an elliptical polar orbit spiraling down to a perilune of 30-10 km above the south pole for data collection. Lunar Flashlight uses its solar sail to shine reflected sunlight into permanently shadowed regions, measuring surface albedo with a four-filter point spectrometer at 1.1, 1.5 1.9, and 2.0 microns. Water ice will be distinguished from dry regolith from these measurements in two ways: 1) spatial variations in absolute reflectance (water ice is much brighter in the continuum channels), and 2) reflectance ratios between absorption and continuum channels. Derived reflectance and reflectance ratios will be mapped onto the lunar surface in order to distinguish the composition of the PSRs from that of the sunlit terrain. Lunar Flashlight enables a low-cost path to in-situ resource utilization (ISRU) by identifying operationally useful deposits (if there are any), which is a game-changing capability for expanded human exploration.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: M14-3629 , NASA''s Solar System Exploration Research Virtual Institute Exploration Science Forum; Jul 21, 2014 - Jul 23, 2014; Moffett Field, CA; United States
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  • 86
    Publikationsdatum: 2019-07-19
    Beschreibung: A fundamental goal of solar system exploration is to understand the origin of the solar sys-tem, the initial stages, conditions, and processes by which the solar system formed, how the formation pro-cess was initiated, and the nature of the interstellar seed material from which the solar system was born. Key to understanding solar system formation and subsequent dynamical and chemical evolution is the origin and evolution of the giant planets and their atmospheres. Several theories have been put forward to explain the process of solar system formation, and the origin and evolution of the giant planets and their atmospheres. Each theory offers quantifiable predictions of the abundances of noble gases He, Ne, Ar, Kr, and Xe, and abundances of key isotopic ratios 4He3He, DH, 15N14N, 18O16O, and 13C12C. Detection of certain dis-equilibrium species, diagnostic of deeper internal pro-cesses and dynamics of the atmosphere, would also help discriminate between competing theories. Measurements of the critical abundance profiles of these key constituents into the deeper well-mixed at-mosphere must be complemented by measurements of the profiles of atmospheric structure and dynamics at high vertical resolution and also require in situ explora-tion. The atmospheres of the giant planets can also serve as laboratories to better understand the atmospheric chem-istries, dynamics, processes, and climates on all planets including Earth, and offer a context and provide a ground truth for exoplanets and exoplanetary systems. Additionally, Giant planets have long been thought to play a critical role in the development of potentially habitable planetary systems. In the context of giant planet science provided by the Galileo, Juno, and Cassini missions to Jupiter and Sat-urn, a small, relatively shallow Saturn probe capable of measuring abundances and isotopic ratios of key at-mospheric constituents, and atmospheric structure in-cluding pressures, temperatures, dynamics, and cloud locations and properties not accessible by remote sens-ing can serve to test competing theories of solar system and giant planet origin, chemical, and dynamical evolution.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: GSFC-E-DAA-TN15235 , International Planetary Probe Workshop; Jun 16, 2014 - Jun 20, 2014; Pasadena, California; United States
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  • 87
    Publikationsdatum: 2019-07-19
    Beschreibung: The Mars Global Reference Atmospheric Model (Mars-GRAM) is an engineering-level atmospheric model widely used for diverse mission and engineering applications. Applications of Mars-GRAM include systems design, performance analysis, and operations planning for aerobraking, entry, descent and landing, and aerocapture. Atmospheric influences on landing site selection and long-term mission conceptualization and development can also be addressed utilizing Mars-GRAM. Mars-GRAM's perturbation modeling capability is commonly used, in a Monte Carlo mode, to perform high-fidelity engineering end-to-end simulations for entry, descent, and landing. Mars-GRAM is an evolving software package resulting in improved accuracy and additional features. Mars-GRAM 2005 has been validated against Radio Science data, and both nadir and limb data from the Thermal Emission Spectrometer (TES). From the surface to 80 km altitude, Mars-GRAM is based on the NASA Ames Mars General Circulation Model (MGCM). Above 80 km, Mars-GRAM is based on the University of Michigan Mars Thermospheric General Circulation Model (MTGCM). The most recent release of Mars-GRAM 2010 includes an update to Fortran 90/95 and the addition of adjustment factors. These adjustment factors are applied to the input data from the MGCM and the MTGCM for the mapping year 0 user-controlled dust case. The adjustment factors are expressed as a function of height (z), latitude and areocentric solar longitude (Ls).
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: M14-3578 , International Conference on Mars; Jul 14, 2014 - Jul 18, 2014; Pasadena, CA; United States
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  • 88
    Publikationsdatum: 2019-07-19
    Beschreibung: Since early 2006, NASA's Marshall Space Flight Center has observed over 300 impact flashes on the Moon, produced by meteoroids striking the lunar surface. On 17 March 2013 at 03:50:54.312 UTC, the brightest flash of an 8-year routine observing campaign was observed in two 0.35 m telescopes outfitted with Watec 902H2 Ultimate monochrome CCD cameras recording interleaved 30 fps video. Standard CCD photometric techniques, described in [1], were applied to the video after saturation correction, yielding a peak R magnitude of 3.0 +/- 0.4 in a 1/30 second video exposure. This corresponds to a luminous energy of 7.1 10(exp 6) J. Geographic Information System (GIS) tools were used to georeference the lunar impact imagery and yielded a crater location at 20.60 +/- 0.17deg N, 23.92 +/- 0.30deg W. The camera onboard the Lunar Reconnaissance Orbiter (LRO), a NASA spacecraft mapping the Moon from lunar orbit, discovered the fresh crater associated with this impact by comparing post-impact images from 28 July 2013 to pre-impact images on 12 Feb 2012. The images show fresh, bright ejecta around an 18 m diameter circular crater, with a 15 m inner diameter measured from the level of pre-existing terrain, at 20.7135deg N, 24.3302deg W. An asymmetrical ray pattern with both high and low reflectance ejecta zones extends 1-2 km beyond the crater, and a series of mostly low reflectance splotches can be seen within 30 km of the crater - likely due to secondary impacts [2]. The meteoroid impactor responsible for this event may have been part of a stream of large particles encountered by the Earth/Moon associated with the Virginid Meteor Complex, as evidenced by a cluster of 5 fireballs seen in Earth's atmosphere on the same night by the NASA All Sky Fireball Network [3] and the Southern Ontario Meteor Network [4]. Assuming a velocity-dependent luminous efficiency (ratio of luminous energy to kinetic energy) from [5] and an impact velocity of 25.6 km/s derived from fireball measurements, the impactor kinetic energy was 5.4 10(exp 9) J and the impactor mass was 16 kg. Assuming an impact angle of 56deg from horizontal (based on fireball orbit measurements), a regolith density of 1500 kg/m(exp 3), and impactor density between 1800 and 3000 kg/m(exp 3), the impact crater diameter was estimated to be 8-18 m at the pre-impact surface and 10-23 m rim-to-rim using the Holsapple [6] and Gault [7] models, a result consistent with the observed crater.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: M14-3528 , Asteroids Comets Meteors (ACM) 2014; Jun 30, 2014 - Jul 04, 2014; Helsinki; Finland
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  • 89
    Publikationsdatum: 2019-07-19
    Beschreibung: Stardust, a NASA Discovery-class mission, was the first sample-return mission to return solid samples from beyond the Moon. Stardust was effectively two missions in one spacecraft: it returned the first materials from a known primitive solar system body, the Jupiter-family comet Wild 2; Stardust also returned a collector that was exposed to the contemporary interstellar dust stream for 200 days during the interplanetary cruise. Both collections present severe technical challenges in sample preparation and in analysis. By far the largest collection is the cometary one: approximately 300 micro g of material was returned from Wild 2, mostly consisting of approx. 1 ng particles embedded in aerogel or captured as residues in craters on aluminum foils. Because of their relatively large size, identification of the impacts of cometary particles in the collection media is straightforward. Reliable techniques have been developed for the extraction of these particles from aerogel. Coordinated analyses are also relatively straightforward, often beginning with synchrotron-based x-ray fluorescence (S-XRF), X-ray Absorption Near-Edge Spectoscopy (XANES) and x-ray diffraction (S-XRD) analyses of particles while still embedded in small extracted wedges of aerogel called ``keystones'', followed by ultramicrotomy and TEM, Scanning Transmission X-ray Microscopy (STXM) and ion microprobe analyses (e.g., Ogliore et al., 2010). Impacts in foils can be readily analyzed by SEM-EDX, and TEM analysis after FIB liftout sample preparation. In contrast, the interstellar dust collection is vastly more challenging. The sample size is approximately six orders of magnitude smaller in total mass. The largest particles are only a few pg in mass, of which there may be only approx.10 in the entire collection. The technical challenges, however, are matched by the scientific importance of the collection. We formed a consortium carry out the Stardust Interstellar Preliminary Examination (ISPE) to carry out an assessment of this collection, partly in order to characterize the collection in sufficient detail so that future investigators could make well-informed sample requests. The ISPE is the sixth PE on extraterrestrial collections carried out with NASA support. Some of the basic questions that we asked were: how many impacts are there in the collector, and what fraction of them have characteristics consistent with extraterrestrial materials? What is the elemental composition of the rock-forming elements? Is there crystalline material? Are there organics? Here we present coordinated microanalyses of particles captured in aerogel, using S-FTIR, S-XRF, STXM, S-XRD; and coordinated microanalyses of residues in aluminum foil, using SEMEDX, Auger spectroscopy, STEM, and ion microprobe. We discuss a novel approach that we employed for identification of tracks in aerogel, and new sample preparation techniques developed during the ISPE. We have identified seven particles - three in aerogel and four in foils - that are most consistent with an interstellar origin. The seven particles exhibit a large diversity in elemental composition. Dynamical evidence, supported supported by laboratory simulations of interstellar dust impacts in aerogel and foils, and numerical modeling of interstellar dust propagation in the heliosphere, suggests that at least some of the particles have high optical cross-section, perhaps due to an aggregate structure. However, the observations are most consistent with a variety of morphologies
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-30654 , Microscopy and Microanalysis 2014; Aug 03, 2014 - Aug 07, 2014; Hartford, CT; United States
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  • 90
    Publikationsdatum: 2019-07-19
    Beschreibung: The martian meteorite Northwest Africa (NWA) 7034 and pairings represent the first brecciated hand sample available for study from the martian surface [1]. Detailed investigations of NWA 7034 have revealed substantial lithologic diversity among the clasts [2-3], making NWA 7034 a polymict breccia. NWA 7034 consists of igneous clasts, impact-melt clasts, and "sedimentary" clasts represented by prior generations of brecciated material. In the present study we conduct a detailed textural and geochemical analysis of the sedimentary clasts.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-31647 , Annual Meeting of the Meteoritical Society; Sep 07, 2014 - Sep 12, 2014; Casablanca; Morocco
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  • 91
    Publikationsdatum: 2019-07-19
    Beschreibung: Howardite, eucrite and diogenite meteorites likely come from asteroid 4 Vesta [1]. Howardites - physical mixtures of eucrites and diogenites - are of two subtypes: regolithic howardites were gardened in the true regolith; fragmental howardites are simple polymict breccias [2]. The Dawn spacecraft imaged the howarditic surface of Vesta with the visible and infrared mapping spectrometer (VIR) resulting in qualitative maps of the distributions of distinct diogenite-rich and eucrite-rich terranes [3, 4]. We are developing a robust basis for quantitative mapping of the distribution of lithologic types using spectra acquired on splits of well-characterized howardites [5, 6]. Spectra were measured on sample powders sieved to 〈75 m in the laboratories of the Istituto di Astrofisica e Planetologia Spaziali and Brown University. Data reduction was done using the methods developed to process Dawn VIR spectra [4]. The band parameters for the ~1 and ~2 m pyroxene absorption features (hereafter BI and BII) can be directly compared to Dawn VIR results. Regolithic howardites have shallower BI and BII absorptions compared to fragmental howardites with similar compositions. However, there are statistically significant correlations between Al or Ca contents and BI or BII center wavelengths regardless of howardite subtype. Diogenites are poor in Al and Ca while eucrites are rich in these elements. The laboratory spectra can thus be directly correlated with the percentage of eucrite material contained in the howardites. We are using these correlations to quantitatively map Al and Ca distributions, and thus the percentage of eucritic material, in the current regolith of Vesta.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-30642 , 2014 Goldschmidt Conference; Jun 08, 2014 - Jun 13, 2014; Sacramento, CA; United States
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  • 92
    Publikationsdatum: 2019-07-19
    Beschreibung: Both primary (volcanic/impact glasses) and secondary (opal/silica, allophane, hisingerite, npOx, S-bearing) amorphous phases appear to be major components of martian surface materials based on orbital and in-situ measurements. A key observation is that whereas regional/global scale amorphous components include altered glass and npOx, local scale amorphous phases include hydrated silica/opal. This suggests widespread alteration at low water-to-rock ratios, perhaps due to snow/ice melt with variable pH, and localized alteration at high water-to-rock ratios. Orbital and in-situ measurements of the regional/global amorphous component on Mars suggests that it is made up of at least three phases: npOx, amorphous silicate (likely altered glass), and an amorphous S-bearing phase. Fundamental questions regarding the composition and the formation of the regional/global amorphous component(s) still remain: Do the phases form locally or have they been homogenized through aeolian activity and derived from the global dust? Is the parent glass volcanic, impact, or both? Are the phases separate or intimately mixed (e.g., as in palagonite)? When did the amorphous phases form? To address the question of source (local and/or global), we need to look for variations in the different phases within the amorphous component through continued modeling of the chemical composition of the amorphous phases in samples from Gale using CheMin and APXS data. If we find variations (e.g., a lack of or enrichment in amorphous silicate in some samples), this may imply a local source for some phases. Furthermore, the chemical composition of the weathering products may give insight into the formation mechanisms of the parent glass (e.g., impact glasses contain higher Al and lower Si [30], so we might expect allophane as a weathering product of impact glass). To address the question of whether these phases are separate or intimately mixed, we need to do laboratory studies of naturally altered samples made up of mixed phases (e.g., palagonite) and synthetic single phases to determine their short-range order structures and calculate their XRD patterns to use in models of CheMin data. Finally, to address the timing of the alteration, we need to study rocks on the martian surface of different ages that may contain glass (volcanic or impact) with MSL and future rovers to better understand how glass alters on the martian surface, if that alteration mechanism is universal, and if alteration spans across long periods of time or if there is a time past which unaltered glass remains.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-31338 , International Conference on Mars; Jul 14, 2014 - Jul 18, 2014; Pasadena, CA; United States
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  • 93
    Publikationsdatum: 2019-07-19
    Beschreibung: New simulation results for the sputtering of lunar soil surface by solar-wind protons and heavy ions will be presented. Previous simulation results showed that the sputtering process has significant effects and plays an important role in changing the surface chemical composition, setting the erosion rate and the sputtering process timescale. In this new work and in light of recent data, we briefly present some theoretical models which have been developed to describe the sputtering process and compare their results with recent calculation to investigate and differentiate the roles and the contributions of potential (or electrodynamic) sputtering from the standard (or kinetic) sputtering.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: M14-3310 , American Physical Society (APS) April Meeting 2014; Mar 05, 2014 - Mar 08, 2014; Savannah, GA; United States
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  • 94
    Publikationsdatum: 2019-07-19
    Beschreibung: This poster presentation will illustrate the use of NASA Lunar Sample Disks and resources to promote scientific inquiry and address the Next Generation Science Standards. The poster will present information on the Lunar Sample Disks, housed and managed by the Astromaterials Research and Exploration Science (ARES) Directorate at the NASA Johnson Space Center. The poster will also present information on an inquirybased planetary sample and impact cratering unit designed to introduce students in grades 410 to the significance of studying the rocks, soils, and surfaces of a planetary world. The unit, consisting of many handson activities, provides context and background information to enhance the impact of the Lunar Sample Disks.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-31323 , Astronomical Society of the Pacific (ASP) Annual Meeting 2014; Aug 02, 2014 - Aug 06, 2014; Burlingame, CA; United States
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  • 95
    Publikationsdatum: 2019-07-19
    Beschreibung: The CheMin X-ray diffraction (XRD) instrument onboard the Mars Science Laboratory rover Curiosity in Gale Crater, Mars, discovered smectite in drill fines of the Sheepbed mudstone at Yellowknife Bay (YNB). The mudstone has a basaltic composition, and the XRD powder diffraction pattern shows smectite 02l diffraction bands peaking at 4.59 A for targets John Klein and Cumberland, consistent with tri-octahedral smectites (saponite). From thermal analysis, the saponite abundance is ~20 wt. %. Among terrestrial analogues we have studied, ferrian saponite from Griffith Park (Los Angeles, CA) gives the best match to the position of the 02l diffraction band of YNB saponites. Here we describe iron-rich saponites from a terrestrial perspective, with a focus on Griffith saponite, and discuss their implications for the mineralogy of Sheepbed saponite and its formation pathways. Iron-rich saponite: Iron-rich saponite on the Earth is recognized as a low-temperature (〈100 C), authigenic alteration product of basalt [e.g., 4-16]. In the discussion that follows, we reference the position of the 02l band because it is a measure of the unit cell 'b' dimension of the octahedral layer and thus the cations (including Fe redox state) in the octahedral layer. Ordinarily, the 06l band near 1.5 A is used to determine the 'b' dimension of smectite, but this band is not accessible with MSL CheMin instrument. For reference, a ferrosaponite (i.e., Fe2+ saponite) studied by [15] has a 02l spacing of 4.72 A and Fe3+/Fe = 0.27 [15]. Samples of terrestrial ferrosaponite, however, are reported to oxidize on the timescale of days when removed from their natural environment and not protected from oxidation. The Griffith saponite is Mg-rich ferrian saponite, and sample AMNH 89172 has an 02l spacing of 4.59 A (same as the Sheepbed saponites) and Fe3+/Fe = 0.64 [3]. This similarity suggests that Sheepbed saponites are ferrian (incompletely oxidized ferrosaponite). More oxidized Griffith saponites (Fe3+/Fe 〉 0.90) have somewhat smaller 02l d-spacings and also show Mossbauer evidence for an XRD amorphous Fe-bearing phase (e.g., ferrihydrite, hisingerite, superparamagnetic ferric oxides, etc.). The Griffith saponite occurs as vesicle fills, as replacements of olivine, and as replacements of mesostasis (basaltic glass). Similar occurrence modes are reported elsewhere. Hisingerite has been proposed by [13] as the alteration product of ferrian saponite whose precursor by oxidation was ferrosaponite.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-31327 , International Conference on Mars; Jul 14, 2014 - Jul 18, 2014; Pasadena, California; United States
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  • 96
    Publikationsdatum: 2019-07-19
    Beschreibung: Depletions of siderophile elements in mantles have placed constraints on the conditions on core segregation and differentiation in bodies such as Earth, Earth's Moon, Mars, and asteroid 4 Vesta. Among the siderophile elements there are a sub-set that are also volatile (volatile siderophile elements or VSE; Ga, Ge, In, As, Sb, Sn, Bi, Zn, Cu, Cd), and thus can help to constrain the origin of volatile elements in these bodies, and in particular the Earth and Moon. One of the fundamental observations of the geochemistry of the Moon is the overall depletion of volatile elements relative to the Earth, but a satisfactory explanation has remained elusive. Hypotheses for Earth include addition during accretion and core formation and mobilized into the metallic core, multiple stage origin, or addition after the core formed. Any explanation for volatile elements in the Earth's mantle must also be linked to an explanation of these elements in the lunar mantle. New metal-silicate partitioning data will be applied to the origin of volatile elements in both the Earth and Moon, and will evaluate theories for exogenous versus endogenous origin of volatile elements.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-30388 , Lunar and Planetary Science Conference; Mar 17, 2014 - Mar 21, 2014; The Woodlands, TX; United States
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  • 97
    Publikationsdatum: 2019-07-19
    Beschreibung: Numerous geophysical and geochemical studies have suggested the existence of a small metallic lunar core, but the composition of that core is not known. Knowledge of the composition can have a large impact on the thermal evolution of the core, its possible early dynamo creation, and its overall size and fraction of solid and liquid. Thermal models predict that the current temperature at the core-mantle boundary of the Moon is near 1650 K. Re-evaluation of Apollo seismic data has highlighted the need for new data in a broader range of bulk core compositions in the PT range of the lunar core. Geochemical measurements have suggested a more volatile-rich Moon than previously thought. And GRAIL mission data may allow much better constraints on the physical nature of the lunar core. All of these factors have led us to determine new phase equilibria experimental studies in the Fe-Ni-S-C-Si system in the relevant PT range of the lunar core that will help constrain the composition of Moon's core.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-30383 , Lunar and Planetary Science Conference; Mar 17, 2014 - Mar 21, 2014; The Woodlands, TX; United States
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  • 98
    Publikationsdatum: 2019-07-19
    Beschreibung: One of the important discoveries from the Stardust mission is the observation of crystalline silicate particles that resemble Ca, Al-rich inclusions (CAIs) and chondrules in carbonaceous chondrites], which suggests radial transport of high temperature solids from the inner to the outer solar nebula regions and capture by accreting cometary objects. The Al-Mg isotope analyses of CAI-like and type II chondrule-like particles revealed no excess of Mg-26 derived from in-situ decay of Al-26 (Tau)(sub 1/2) = 0.705Myr; ), suggesting late formation of these particles. However, the number of Wild 2 particles analyzed for Al-Mg isotopes is still limited (n = 3). In order to better understand the timing of the formation of Wild 2 particles and possible radial transport in the protoplanetary disk, we performed SIMS (Secondary Ion Mass Spectrometer) Al-Mg isotope analyses of plagioclase in a FeO-poor ferromagnesian Wild 2 particle, which is the most abundant type among crystalline Wild 2 particles.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-30360 , Lunar and Planetary Science Conference; Mar 17, 2014 - Mar 21, 2014; The Woodlands, TX; United States
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  • 99
    Publikationsdatum: 2019-07-19
    Beschreibung: Major occurrences of hydrous alteration minerals on Mars have been found in Noachian impact craters formed in basaltic targets and detected using visible/near infrared (VNIR) spectroscopy. Until recently phyllosilicates were detected only in craters in the southern hemisphere [1, 2]. However, it has been reported that at least nine craters in the northern plains apparently excavated thick layers of lava and sediment to expose phyllosilicates [3] as well. The MER (Mars Exploration Rovers) rovers previously reported results of in situ measurement indicating the presence of alteration minerals on Mars [4,5] and it was recently reported that the Mars Curiosity rover has detected alteration phases in situ at Yellowknife Bay in Gale crater as well [6,7]. An important discovery for Mars geochronology is that the Chemistry and Mineralogy (CheMin) x-ray diffraction (XRD) instrument on Curiosity detected phyllosilicates indicating that phyllosilicate formation on Mars extended beyond the Noachian Epoch [8]. These discoveries indicate that Mars was globally altered by water in the past but does not constrain formation conditions for alteration phase occurrences, which have important implications for the evolution of the surface and the biological potential on Mars. Understanding the alteration assemblages produced by a range of conditions is vital for the interpretation of phyllosilicate spectral signatures as well as in situ measurements and to decipher the environment and evolution of early Mars. The martian surface has been intensely altered by meteorite impacts whose effects include brecciation and melting of target materials as well as the initiation of hydrothermal circulation in a hydrous target [9,10,11,12]. Impact effects may facilitate aqueous alteration of a basaltic target because the rate of silicate dissolution is a function of the degree of crystallinity, surface area, and temperature. The resultant alteration mineralogies from shocked basaltic target material are a function of the original mineral assemblage in the parent rocks, the chemistry of fluids that interacted with the rocks, and physico-chemical conditions (pH, temperatures, and pressure) during the time of mineral formation. Understanding the alteration assemblages produced by a range of conditions is vital for the interpretation of phyllosilicate spectral signatures and to decipher the environment and evolution of early Mars, and especially for identifying habitable niches in which life could be initiated and sustained. No experimentally controlled and well characterized analog materials that simulate martian shock metamorphism and alteration conditions currently exist for calibrating either remote sensing or in situ measurements of Mars. A series of experiments was initiated to assess the effects of systematic changes in the physico-chemical conditions on Mars analog materials thereby providing samples to ground-truth Mars remote sensing observations from CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) and in situ measurements from Opportunity's Mssbauer and Curiosity's CHEMIN (Chemistry and Mineralogy X-Ray Diffraction/XRay Fluorescence) instruments. Results of initial experimental runs as analysed by SEM-EDS (Secondary Electron Microscopy -Energy Dispersive Spectroscopy) and X-ray Diffraction (XRD) analysis are reported here and lay the foundation for comparison with shocked and altered samples that will be characterized in the next phase of this work.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: JSC-CN-30323 , Lunar and Planetary Science Conference; Mar 17, 2014 - Mar 21, 2014; The Woodlands, TX; United States
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  • 100
    Publikationsdatum: 2019-07-19
    Beschreibung: We present results on the formation of Titan aerosol analogs produced via far-UV irradiation of five aromatic precursors: benzene, naphthalene, pyridine, quinoline and isoquinoline. This is the first reported evidence of far-IR emission features observed below 200 per cm in laboratory-created Titan aerosols. These laboratory studies were motivated by recent analyses of Cassini Composite Infrared Spectrometer (CIRS) spectra that show a broad aerosol emission feature in the far-IR spectral region centered near 140 per cm, which is unique to Titan's photochemically-produced aerosol. We find that all three of the aerosol analogs formed from nitrogen-containing aromatics have similar broad emission features near that of the observed CIRS far-IR aerosol spectral feature. In addition, the inclusion of 1.5% methane to that of trace amounts of benzene also gives rise to an aerosol with a weak far-IR emission feature located below 200 per cm.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: GSFC-E-DAA-TN18137
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