ALBERT

Description: The total electron content (TEC) of a planetary ionosphere is dominated by plasma near and above the height of maximum electron density (N max ). The ratio TEC/N max represents the thickness (τ) of a TEC slab of uniform density (N max ). For a photo-chemical ionosphere, τ relates to the scale height (H=kT/mg) of the ionized neutral gas as τ ~ 4xH. Derived temperatures refer to ~160 km in thermosphere height—below the asymptotic temperature of the exosphere. The MARSIS instrument on Mars Express has produced data sets of TEC and N max . We used them to form τ patterns versus solar zenith angle and solar cycle phase. For daytime (SZA〈90°) conditions, 〈τ〉 day ~50km, decreasing rapidly for SZA〉90° to 〈τ〉 night ~25km. These correspond to T n values of 250°K and 125°K. Using Mars Global Surveyor data, τ patterns show a mild dependence upon the solar EUV flux proxy F10.7, with ΔT n (°K)~0.3° per unit change in F10.7 at Mars.

Description: The ice-rich south polar layered deposits of Mars were probed with the Mars Advanced Radar for Subsurface and Ionospheric Sounding on the Mars Express orbiter. The radar signals penetrate deep into the deposits (more than 3.7 kilometers). For most of the area, a reflection is detected at a time delay that is consistent with an interface between the deposits and the substrate. The reflected power from this interface indicates minimal attenuation of the signal, suggesting a composition of nearly pure water ice. Maps were generated of the topography of the basal interface and the thickness of the layered deposits. A set of buried depressions is seen within 300 kilometers of the pole. The thickness map shows an asymmetric distribution of the deposits and regions of anomalous thickness. The total volume is estimated to be 1.6 x 10(6) cubic kilometers, which is equivalent to a global water layer approximately 11 meters thick.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Plaut, Jeffrey J -- Picardi, Giovanni -- Safaeinili, Ali -- Ivanov, Anton B -- Milkovich, Sarah M -- Cicchetti, Andrea -- Kofman, Wlodek -- Mouginot, Jeremie -- Farrell, William M -- Phillips, Roger J -- Clifford, Stephen M -- Frigeri, Alessandro -- Orosei, Roberto -- Federico, Costanzo -- Williams, Iwan P -- Gurnett, Donald A -- Nielsen, Erling -- Hagfors, Tor -- Heggy, Essam -- Stofan, Ellen R -- Plettemeier, Dirk -- Watters, Thomas R -- Leuschen, Carlton J -- Edenhofer, Peter -- New York, N.Y. -- Science. 2007 Apr 6;316(5821):92-5. Epub 2007 Mar 15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17363628" target="_blank"〉PubMed〈/a〉

Description: The martian subsurface has been probed to kilometer depths by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument aboard the Mars Express orbiter. Signals penetrate the polar layered deposits, probably imaging the base of the deposits. Data from the northern lowlands of Chryse Planitia have revealed a shallowly buried quasi-circular structure about 250 kilometers in diameter that is interpreted to be an impact basin. In addition, a planar reflector associated with the basin structure may indicate the presence of a low-loss deposit that is more than 1 kilometer thick.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Picardi, Giovanni -- Plaut, Jeffrey J -- Biccari, Daniela -- Bombaci, Ornella -- Calabrese, Diego -- Cartacci, Marco -- Cicchetti, Andrea -- Clifford, Stephen M -- Edenhofer, Peter -- Farrell, William M -- Federico, Costanzo -- Frigeri, Alessandro -- Gurnett, Donald A -- Hagfors, Tor -- Heggy, Essam -- Herique, Alain -- Huff, Richard L -- Ivanov, Anton B -- Johnson, William T K -- Jordan, Rolando L -- Kirchner, Donald L -- Kofman, Wlodek -- Leuschen, Carlton J -- Nielsen, Erling -- Orosei, Roberto -- Pettinelli, Elena -- Phillips, Roger J -- Plettemeier, Dirk -- Safaeinili, Ali -- Seu, Roberto -- Stofan, Ellen R -- Vannaroni, Giuliano -- Watters, Thomas R -- Zampolini, Enrico -- New York, N.Y. -- Science. 2005 Dec 23;310(5756):1925-8. Epub 2005 Nov 30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Infocom Department, "La Sapienza" University of Rome, 00184 Rome, Italy.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16319122" target="_blank"〉PubMed〈/a〉

Description: Mars' polar regions are covered with ice-rich layered deposits that potentially contain a record of climate variations. The sounding radar SHARAD on the Mars Reconnaissance Orbiter mapped detailed subsurface stratigraphy in the Promethei Lingula region of the south polar plateau, Planum Australe. Radar reflections interpreted as layers are correlated across adjacent orbits and are continuous for up to 150 kilometers along spacecraft orbital tracks. The reflectors are often separated into discrete reflector sequences, and strong echoes are seen as deep as 1 kilometer. In some cases, the sequences are dipping with respect to each other, suggesting an interdepositional period of erosion. In Australe Sulci, layers are exhumed, indicating recent erosion.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Seu, Roberto -- Phillips, Roger J -- Alberti, Giovanni -- Biccari, Daniela -- Bonaventura, Francesco -- Bortone, Marco -- Calabrese, Diego -- Campbell, Bruce A -- Cartacci, Marco -- Carter, Lynn M -- Catallo, Claudio -- Croce, Anna -- Croci, Renato -- Cutigni, Marco -- Di Placido, Antonio -- Dinardo, Salvatore -- Federico, Costanzo -- Flamini, Enrico -- Fois, Franco -- Frigeri, Alessandro -- Fuga, Oreste -- Giacomoni, Emanuele -- Gim, Yonggyu -- Guelfi, Mauro -- Holt, John W -- Kofman, Wlodek -- Leuschen, Carlton J -- Marinangeli, Lucia -- Marras, Paolo -- Masdea, Arturo -- Mattei, Stefania -- Mecozzi, Riccardo -- Milkovich, Sarah M -- Morlupi, Antonio -- Mouginot, Jeremie -- Orosei, Roberto -- Papa, Claudio -- Paterno, Tobia -- Persi del Marmo, Paolo -- Pettinelli, Elena -- Pica, Giulia -- Picardi, Giovanni -- Plaut, Jeffrey J -- Provenziani, Marco -- Putzig, Nathaniel E -- Russo, Federica -- Safaeinili, Ali -- Salzillo, Giuseppe -- Santovito, Maria Rosaria -- Smrekar, Suzanne E -- Tattarletti, Barbara -- Vicari, Danilo -- New York, N.Y. -- Science. 2007 Sep 21;317(5845):1715-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Dipartimento INFOCOM, Universita di Roma "La Sapienza," I-00184 Rome, Italy. roberto.seu@uniroma1.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17885128" target="_blank"〉PubMed〈/a〉

Description: The Philae lander provides a unique opportunity to investigate the internal structure of a comet nucleus, providing information about its formation and evolution in the early solar system. We present Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) measurements of the interior of Comet 67P/Churyumov-Gerasimenko. From the propagation time and form of the signals, the upper part of the "head" of 67P is fairly homogeneous on a spatial scale of tens of meters. CONSERT also reduced the size of the uncertainty of Philae's final landing site down to approximately 21 by 34 square meters. The average permittivity is about 1.27, suggesting that this region has a volumetric dust/ice ratio of 0.4 to 2.6 and a porosity of 75 to 85%. The dust component may be comparable to that of carbonaceous chondrites.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kofman, Wlodek -- Herique, Alain -- Barbin, Yves -- Barriot, Jean-Pierre -- Ciarletti, Valerie -- Clifford, Stephen -- Edenhofer, Peter -- Elachi, Charles -- Eyraud, Christelle -- Goutail, Jean-Pierre -- Heggy, Essam -- Jorda, Laurent -- Lasue, Jeremie -- Levasseur-Regourd, Anny-Chantal -- Nielsen, Erling -- Pasquero, Pierre -- Preusker, Frank -- Puget, Pascal -- Plettemeier, Dirk -- Rogez, Yves -- Sierks, Holger -- Statz, Christoph -- Svedhem, Hakan -- Williams, Iwan -- Zine, Sonia -- Van Zyl, Jakob -- New York, N.Y. -- Science. 2015 Jul 31;349(6247):aab0639. doi: 10.1126/science.aab0639.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Universite Grenoble Alpes, IPAG, F-38000 Grenoble, France (2) Centre National de la Recherche Scientifique (CNRS), Institut de Planetologie et d'Astrophysique de Grenoble (IPAG), F-38000 Grenoble, France. ; MIO, UM 110, CNRS-Institut National des Sciences de l'Univers (INSU), Universite de Toulon, Aix-Marseille Universite, IRD 83957 La Garde, France. ; Geodesy Observatory of Tahiti BP6570, 98702 Faa'a, Tahiti. ; Universite de Versailles Saint-Quentin-en-Yvelines (UVSQ) (UPSay); Universite Pierre et Marie Curie (UPMC) (Sorbonne Univ.); CNRS/INSU; Laboratoire Atmospheres, Milieux, Observations Spatiales (LATMOS)-Institut Pierre-Simon Laplace (IPSL), 11 Boulevard d'Alembert, 78280 Guyancourt, France. ; Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, USA. ; Ruhr-University of Bochum, Faculty of Electrical Engineering and Information Technology, 44780 Bochum, Germany. ; Jet Propulsion Laboratory, 4800 Oak Grove Drive, MS 300-243E, Pasadena, CA 91109, USA. ; Aix-Marseille Universite, CNRS, Centrale Marseille, Institut Fresnel UMR 7249, 13013 Marseille, France. ; Jet Propulsion Laboratory, 4800 Oak Grove Drive, MS 300-243E, Pasadena, CA 91109, USA. University of Southern California, Ming Hsieh Department of Electrical Engineering, Viterbi School of Engineering, Los Angeles, CA 90089, USA. ; Laboratoire d'Astrophysique de Marseille Pole de l'Etoile Site de Chateau-Gombert 38, Rue Frederic Joliot-Curie 13388 Marseille, France. ; Universite de Toulouse; UPS-OMP; IRAP; (2) CNRS; IRAP; 9 Avenue Colonel Roche, BP 44 346, F-31028 Toulouse Cedex 4, Toulouse, France. ; UPMC (Sorbonne Univ.); UVSQ (UPSay); CNRS/INSU; LATMOS-IPSL, BC 102, 4 place Jussieu, 75005 Paris, France. ; Max-Planck-Institut fur Sonnensystemforschung (MPS), Justus-von-Liebig-Weg 3, 37077 Gottingen, Germany. ; German Aerospace Center (DLR) Rutherfordstrasse 2 12489 Berlin, Germany. ; Technische Universitaet Dresden Helmholtzstrasse 10 D-01069 Dresden, Germany. ; European Space Agency (ESA)/European Space Research and Technology Centre (ESTEC) Noordwijk, Netherlands. ; Queen Mary University of London, Mile End Road, London E1 4NS, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26228153" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bibring, J-P -- Taylor, M G G T -- Alexander, C -- Auster, U -- Biele, J -- Finzi, A Ercoli -- Goesmann, F -- Klingelhoefer, G -- Kofman, W -- Mottola, S -- Seidensticker, K J -- Spohn, T -- Wright, I -- New York, N.Y. -- Science. 2015 Jul 31;349(6247):493. doi: 10.1126/science.aac5116. Epub 2015 Jul 30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut d'Astrophysique Spatiale, Orsay, France. ; European Space Research and Technology Centre, Noordwijk, Netherlands. ; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, deceased. ; Institute for Geophysics and Extraterrestrial Physics, TU-Braunschweig, Germany. ; DLR RB-MUSC, Cologne, Germany. ; Politecnico di Milano, Milan, Italy. ; Max Planck Institute for Solar System Research, Gottingen, Germany. ; University of Mainz, Mainz, Germany. ; Institut de Planetologie et d'Astrophysique de Grenoble, Grenoble, France. ; DLR, Institute of Planetary Research, Berlin, Germany. ; Open University, Milton Keynes, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26228139" target="_blank"〉PubMed〈/a〉

Description: The Philae lander, part of the Rosetta mission to investigate comet 67P/Churyumov-Gerasimenko, was delivered to the cometary surface in November 2014. Here we report the precise circumstances of the multiple landings of Philae, including the bouncing trajectory and rebound parameters, based on engineering data in conjunction with operational instrument data. These data also provide information on the mechanical properties (strength and layering) of the comet surface. The first touchdown site, Agilkia, appears to have a granular soft surface (with a compressive strength of 1 kilopascal) at least ~20 cm thick, possibly on top of a more rigid layer. The final landing site, Abydos, has a hard surface.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Biele, Jens -- Ulamec, Stephan -- Maibaum, Michael -- Roll, Reinhard -- Witte, Lars -- Jurado, Eric -- Munoz, Pablo -- Arnold, Walter -- Auster, Hans-Ulrich -- Casas, Carlos -- Faber, Claudia -- Fantinati, Cinzia -- Finke, Felix -- Fischer, Hans-Herbert -- Geurts, Koen -- Guttler, Carsten -- Heinisch, Philip -- Herique, Alain -- Hviid, Stubbe -- Kargl, Gunter -- Knapmeyer, Martin -- Knollenberg, Jorg -- Kofman, Wlodek -- Komle, Norbert -- Kuhrt, Ekkehard -- Lommatsch, Valentina -- Mottola, Stefano -- Pardo de Santayana, Ramon -- Remetean, Emile -- Scholten, Frank -- Seidensticker, Klaus J -- Sierks, Holger -- Spohn, Tilman -- New York, N.Y. -- Science. 2015 Jul 31;349(6247):aaa9816. doi: 10.1126/science.aaa9816.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Deutsches Zentrum fur Luft- und Raumfahrt (DLR)/Raumflugbetrieb und Astronautentraining, Microgravity User Support Center (MUSC), Linder Hohe 1, 51147 Cologne, Germany. ; Max-Planck-Institut fur Sonnensystemforschung (MPS), Justus-von-Liebig-Weg 3, 37077 Gottingen, Germany. ; DLR/Institut fur Raumfahrtsysteme, Robert Hooke-Strasse 7, 28359 Bremen, Germany. ; Centre National d'Etudes Spatiales, 18 Avenue Edouard Belin, 31400 Toulouse, France. ; European Space Agency/European Space Operations Centre (ESA/ESOC), Robert-Bosch-Strasse 5, 64293 Darmstadt, Germany. Grupo Mecanica de Vuelo at ESA/ESOC - GMV Robert-Bosch-Strasse 5, 64293 Darmstadt, Germany. ; 1. Physikalisches Institut, Georg August Universitat, 37077 Gottingen, Germany; permanent address: Department of Materials Science, Saarland University, 66123 Saarbrucken, Germany. ; Institut fur Geophysik und Extraterrestrische Physik, Technische Universitat Braunschweig Mendelssohnstrasse 3, 38106 Braunschweig, Germany. ; DLR/Institut fur Planetenforschung Rutherfordstrasse 2, 12489 Berlin, Germany. ; Universite Grenoble Alpes and CNRS, Institut de Planetologie et d'Astrophysique de Grenoble, F-38000 Grenoble, France. ; Institut fur Weltraumforschung (IWF) Graz, Austria Austrian Academy of Sciences, Space Research Institute, Schmiedlstrasse 6, 8042 Graz, Austria.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26228158" target="_blank"〉PubMed〈/a〉

Description: The internal properties of porous and icy bodies in the Solar System can be investigated by ground-penetrating radars (GPRs), like the CONSERT instrument onboard the Rosetta spacecraft which has sounded the interior of the nucleus of comet 67P/C-G. Accurate constraints on the permittivity of icy media are needed for the interpretation of the data. We report novel permittivity measurements performed on water ice samples and icy mixtures with porosities in the 31–91% range. The measurements have been performed between 50 MHz and 2 GHz with a coaxial cell on a total of 38 samples with a good reproducibility. We used controlled procedures to produce fine-grained and coarse-grained ice samples with a mean diameter of 4.5 μ m and 67 μ m, respectively, and to prepare icy mixtures. The JSC-1A Lunar regolith simulant was used as the dust component in the mixtures. The results are focused on the real part ε ′ of the permittivity, which constrains the phase velocity of the radio waves in low-loss media. The values of ε ′ show a non-dispersive behavior and are within the range of 1.1 to 2.7. They decrease with the increasing porosity Φ according to E (1 − Φ ) , with E equal to about 3.13 for pure water ice, and in the 3.8–7.5 range for ice-dust mixtures with a dust-to-ice volumetric ratio in the 0.1–2.8 range, respectively. These measurements are also relevant for radiometers operating in the millimeter-submillimeter domains, as suggested by the non-dispersive behavior of the mixtures and of the pure components.

Description: The total electron content (TEC) is one of the most useful parameters to evaluate the behavior of the martian ionosphere because it contains information on the total amount of free electrons, the main component of the martian ionospheric plasma. The Mars Express MARSIS radar is able to derive TEC from both of its operations modes: (1) the active ionospheric sounding (AIS) mode, and (2) the subsurface mode. TEC estimates from the subsurface sounding mode can be computed from the same raw data independently using different algorithms, which should yield similar results. Significant differences on the dayside, however, have been found from two of the algorithms. Moreover, both algorithms seem also to disagree with the TEC results from the AIS mode. This paper gives a critical, quantitative and independent assessment of these discrepancies, and indicates the possible uncertainty of these databases. In addition, a comparison between the results given by the empirical model of the martian ionosphere developed by Sánchez-Cano et al. (2013) and the different datasets has been performed. The main result is that for solar zenith angles higher than 75 degrees, where the maximum plasma frequency is typically small compared with the radar frequencies, the two subsurface algorithms can be confidently used. For solar zenith angles less than 75 degrees, where the maximum plasma frequency is very close to the radar frequencies, both algorithms suffer limitations. Nevertheless, despite the solar zenith angle restrictions, the dayside TEC of one of the two algorithms is consistent with the modelled TEC.