ALBERT

Description: Many studies exist on magmatic volatiles (H, C, N, F, S, Cl) in and on the Moon, within the last several years, that have cast into question the post-Apollo view of lunar formation, the distribution and sources of volatiles in the Earth-Moon system, and the thermal and magmatic evolution of the Moon. However, these recent observations are not the first data on lunar volatiles. When Apollo samples were first returned, substantial efforts were made to understand volatile elements, and a wealth of data regarding volatile elements exists in this older literature. In this review paper, we approach volatiles in and on the Moon using new and old data derived from lunar samples and remote sensing. From combining these data sets, we identified many points of convergence, although numerous questions remain unanswered. The abundances of volatiles in the bulk silicate Moon (BSM), lunar mantle, and urKREEP [last ~1% of the lunar magma ocean (LMO)] were estimated and placed within the context of the LMO model. The lunar mantle is likely heterogeneous with respect to volatiles, and the relative abundances of F, Cl, and H 2 O in the lunar mantle (H 2 O 〉 F 〉〉 Cl) do not directly reflect those of BSM or urKREEP (Cl 〉 H 2 O F). In fact, the abundances of volatiles in the cumulate lunar mantle were likely controlled by partitioning of volatiles between LMO liquid and nominally anhydrous minerals instead of residual liquid trapped in the cumulate pile. An internally consistent model for lunar volatiles in BSM should reproduce the absolute and relative abundances of volatiles in urKREEP, the anorthositic primary crust, and the lunar mantle within the context of processes that occurred during the thermal and magmatic evolution of the Moon. Using this mass-balance constraint, we conducted LMO crystallization calculations with a specific focus on the distributions and abundances of F, Cl, and H 2 O to determine whether or not estimates of F, Cl, and H 2 O in urKREEP are consistent with those of the lunar mantle, estimated independently from the analysis of volatiles in mare volcanic materials. Our estimate of volatiles in the bulk lunar mantle are 0.54–4.5 ppm F, 0.15–5.3 ppm H 2 O, 0.26–2.9 ppm Cl, 0.014–0.57 ppm C, and 78.9 ppm S. Our estimates of H 2 O are depleted compared to independent estimates of H 2 O in the lunar mantle, which are largely biased toward the "wettest" samples. Although the lunar mantle is depleted in volatiles relative to Earth, unlike the Earth, the mantle is not the primary host for volatiles. The primary host of the Moon’s incompatible lithophile volatiles (F, Cl, H 2 O) is urKREEP, which we estimate to have 660 ppm F, 300–1250 ppm H 2 O, and 1100–1350 ppm Cl. This urKREEP composition implies a BSM with 7.1 ppm F, 3–13 ppm H 2 O, and 11–14 ppm Cl. An upper bound on the abundances of F, Cl, and H 2 O in urKREEP and the BSM, based on F abundances in CI carbonaceous chondrites, are reported to be 5500 ppm F, 0.26–1.09 wt% H 2 O, and 0.98–1.2 wt% Cl and 60 ppm F, 27–114 ppm H 2 O, and 100–123 ppm Cl, respectively. The role of volatiles in many lunar geologic processes was also determined and discussed. Specifically, analyses of volatiles from lunar glass beads as well as the phase assemblages present in coatings on those beads were used to infer that H 2 is likely the primary vapor component responsible for propelling the fire-fountain eruptions that produced the pyroclastic glass beads (as opposed to CO). The textural occurrences of some volatile-bearing minerals are used to identify hydrothermal alteration, which is manifested by sulfide veining and sulfide-replacement textures in silicates. Metasomatic alteration in lunar systems differs substantially from terrestrial alteration due to differences in oxygen fugacity between the two bodies that result in H 2 O as the primary solvent for alteration fluids on Earth and H 2 as the primary solvent for alteration fluids on the Moon (and other reduced planetary bodies). Additionally, volatile abundances in volatile-bearing materials are combined with isotopic data to determine possible secondary processes that have affected the primary magmatic volatile signatures of lunar rocks including degassing, assimilation, and terrestrial contamination; however, these processes prove difficult to untangle within individual data sets. Data from remote sensing and lunar soils are combined to understand the distribution, origin, and abundances of volatiles on the lunar surface, which can be explained largely by solar wind implantation and spallogenic processes, although some of the volatiles in the soils may also be either indigenous to the Moon or terrestrial contamination. We have also provided a complete inventory of volatile-bearing mineral phases indigenous to lunar samples and discuss some of the "unconfirmed" volatile-bearing minerals that have been reported. Finally, a compilation of unanswered questions and future avenues of research on the topic of lunar volatiles are presented, along with a critical analysis of approaches for answering these questions.

Description: Fans, landforms that record the storage and transport of sediment from uplands to depositional basins, are found on Saturn's moon Titan, a body of significantly different process rates and material compositions from Earth. Images obtained by the Cassini spacecraft's synthetic aperture radar reveal morphologies, roughness, textural patterns and other properties consistent with fan analogues on Earth also viewed by synthetic aperture radar. The observed fan characteristics on Titan reveal some regions of high relative relief and others with gentle slopes over hundreds of kilometres, exposing topographic variations and influences on fan formation. There is evidence for a range of particle sizes across proximal to distal fan regions, from c. 2 cm or more to fine-grained, which can provide details on sedimentary processes. Some features are best described as alluvial fans, which implies their proximity to high-relief source areas, while others are more likely to be fluvial fans, drawing from larger catchment areas and frequently characterized by more prolonged runoff events. The presence of fans corroborates the vast liquid storage capacity of the atmosphere and the resultant episodic behaviour. Fans join the growing list of landforms on Titan derived from atmospheric and fluvial processes similar to those on Earth, strengthening comparisons between these two planetary bodies.

Description: Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.

Description: Author(s): W. Bartmann, M. Atanasov, M. J. Barnes, J. Borburgh, F. Burkart, B. Goddard, T. Kramer, A. Lechner, A. Sanz Ull, R. Schmidt, L. S. Stoel, R. Ostojic, J. Rodziewicz, P. van Trappen, and D. Barna The Future Circular Collider (FCC-hh) beam dump system must provide a safe and reliable extraction and dilution of the stored beam onto a dump absorber. Energy deposition studies show that damage limits of presently used absorber materials will already be reached for single bunches at 50 TeV. A fast… [Phys. Rev. Accel. Beams 20, 031001] Published Fri Mar 10, 2017

Description: A statistical based method combined with basis function expansion techniques is described in order to provide extensive maps of the ground level perturbation magnetic field from 40 0 magnetic latitude to the north magnetic pole for all longitudes. The method combines historical data from the SuperMAG data base, Principal Component Analysis and a spherical cap harmonic basis function expansion in order to fill in magnetic perturbation data where there are no magnetometers and produce the poloidal current potential. The maps have a regular grid with a 2 0 latitude and 1 hour longitude spacing. The statistical process uses SuperMAG data derived magnetic indices plus the solar zenith angle which orders the resulting spatial maps by geomagnetic activity indicators to enhance model agreement with the data. For quiet through to moderate magnetic activity intervals, the root mean square error between the input and the fitted data are 18 nT and 10 nT for the north-south and east-west components respectively, which are of similar magnitude to the statistical uncertainty in the SuperMAG data set.

Description: Mount Keith is a large (up to 500 m thick, and 〉2 km long) serpentinized and talc-carbonate-altered dunite body. The geologic features of Mount Keith are similar to many of the ultramafic bodies in the Agnew-Wiluna belt and other greenstone belts within the eastern Yilgarn craton. Mount Keith hosts a large disseminated nickel sulfide orebody that is presently exploited by open pit. There are currently two hypotheses that explain the site of formation of these dunite bodies: either kilometer-scale komatiite lava channels, or subvolcanic sills intruded into the greenstone sequence are responsible. The intrusive model is essentially based on two pieces of geologic evidence: the presence of a single 20-m-scale and single 20-cm-scale ultramafic apophysis in overlying dacitic rocks; and the presence of dacite inclusions within the contact zone of the upper part of the Mount Keith ultramafic unit. New geologic data show that the western part of the Mount Keith ultramafic unit and the overlying dacite sequence are allochthonous and that the contact zone between the two comprises multiple anastomosing layer-parallel fault slices of both lithologies at a scale of meters to tens of meters. Within some of the fault blocks, primary igneous contacts are present between the top of the Mount Keith ultramafic unit and the overlying dacite. New evidence shows that both pyroxene and minor olivine spinifex-textured rocks are present along much of the upper preserved part of the Mount Keith ultramafic unit and pseudomorphs after pyroxene grains exist on a scale of 20 to 200 μ m that formed during emplacement and survived the cooling of the 500-m-thick Mount Keith ultramafic unit. Moreover, the evidence for a large-scale ultramafic intrusive apophysis is unsubstantiated, as this apophysis is shown to be a slice within a brittle/ductile fault. The reinterpretation of the small-scale apophysis is consistent with this being an ultramafic enclave within a younger dacite flow. Finally, the dacite exposed within centimeters to meters of the western ultramafic contact commonly retains delicate igneous textures and shows no evidence of thermal effects from the Mount Keith ultramafic unit. Modeling of the heat budget assuming the dimensions of the Mount Keith ultramafic unit shows that an intrusion of this size should have produced wholesale melting of roof rocks. Our findings indicate that the Western Dacite sequence was not present above the Mount Keith ultramafic unit during its emplacement and cooling. A model is favored for the extrusive origin of the Mount Keith ultramafic unit with construction of the olivine cumulate pile at the floor of an approximately 2-km-wide, intermittently sulfide-bearing, turbulent lava pathway. At the terminal stages of eruption magma flow decreased and finally ceased, allowing the lava to drain and cause the upper crust to collapse onto the top of the crystal pile, producing in places sharp juxtaposition of chilled margin rocks with coarse-grained olivine cumulates. In most places rapid flow and turbulent convection resulted in resorption of the crust, but local formation of stagnant ponds allowed survival of an olivine spinifex-textural profile. More extensive ponding of the magma allowed in situ fractionation and formation of gabbroic and pyroxenitic rocks derived from highly fractionated komatiite magma. The Mount Keith ultramafic unit is believed to be the product of extrusive magmatism from which an olivine cumulate pile developed by upward accretion at the floor of a major lava pathway; these rocks were then extensively modified by deformation.

Description: ABSTRACT In airborne gravity gradiometry, the Gravity Module Assembly is an optional gravimeter unit that is mounted on the same stabilized platform as the Full Tensor Gradiometer. Direct measurements of the gravity field are needed from this device to constrain the long wavelengths when gradient data are integrated mathematically to form high‐resolution gravity fields. The Gravity Module Assembly is, however, capable of providing independent gravity data with a specification approaching that expected from a dedicated airborne gravity system. Presented here is an error analysis of data from this instrument collected alongside the Full Tensor Gradiometer during an airborne survey. By having both gradiometry and gravity datasets, comparisons of the information content in these two types of measurement are made.

Description: 〈p〉Harnessing the potential of human stem cells for modeling the physiology and diseases of cortical circuitry requires monitoring cellular dynamics in vivo. We show that human induced pluripotent stem cell (iPSC)–derived cortical neurons transplanted into the adult mouse cortex consistently organized into large (up to ~100 mm〈sup〉3〈/sup〉) vascularized neuron-glia territories with complex cytoarchitecture. Longitudinal imaging of 〉4000 grafted developing human neurons revealed that neuronal arbors refined via branch-specific retraction; human synaptic networks substantially restructured over 4 months, with balanced rates of synapse formation and elimination; and oscillatory population activity mirrored the patterns of fetal neural networks. Lastly, we found increased synaptic stability and reduced oscillations in transplants from two individuals with Down syndrome, demonstrating the potential of in vivo imaging in human tissue grafts for patient-specific modeling of cortical development, physiology, and pathogenesis.〈/p〉

Description: Cranial neural crest cells (crNCCs) migrate from the neural tube to the pharyngeal arches (PAs) of the developing embryo and, subsequently, differentiate into bone and connective tissue to form the mandible. Within the PAs, crNCCs respond to local signaling cues to partition into the proximo-distally oriented subdomains that convey positional...