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4. Radar Soundings of the Subsurface of Mars

Author

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., 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., and Zampolini, Enrico

Published
2005

5. List of Contributors

Author

Bridges, John C., primary, Butcher, Frances E.G., additional, Clifford, Stephen M., additional, Conway, Susan J., additional, Farrand, William H., additional, Filiberto, Justin, additional, Franz, Heather B., additional, Gaillard, Fabrice, additional, Gellert, Ralf, additional, Hicks, Leon J., additional, Jolliff, Bradley L., additional, King, Penelope L., additional, Knoll, Andrew H., additional, Kounaves, Samuel P., additional, Lasue, Jérémie, additional, Mahaffy, Paul R., additional, Mangold, Nicolas, additional, McAdam, Amy C., additional, McCubbin, Francis M., additional, McLennan, Scott M., additional, Ming, Douglas W., additional, Mittlefehldt, David W., additional, Mustard, John F., additional, Oberlin, Elizabeth A., additional, Olsson-Francis, Karen, additional, Ott, Ulrich, additional, Schwenzer, Susanne P., additional, Sutter, Brad, additional, Swindle, Timothy D., additional, Taylor, G. Jeffrey, additional, Treiman, Allan H., additional, Usui, Tomohiro, additional, and Yen, Albert S., additional

Published
2019
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9. A cold hydrological system in Gale crater, Mars

Author

Fairén, Alberto G., Stokes, Chris R., Davies, Neil S., Schulze-Makuch, Dirk, Rodríguez, J. Alexis P., Davila, Alfonso F., Uceda, Esther R., Dohm, James M., Baker, Victor R., Clifford, Stephen M., McKay, Christopher P., and Squyres, Steven W.

Published
2014
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13. Subsurface Radar Sounding of the South Polar Layered Deposits of Mars

Author

Plaut, Jeffrey J., Picardi, Giovanni, Safaeinili, Ali, Ivanov, Anton B., Milkovich, Sarah M., Cicchetti, Andrea, Kofman, Wlodek, Mouginot, Jérémie, 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., and Edenhofer, Peter

Published
2007
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14. MARSIS radar sounder evidence of buried basins in the northern lowlands of Mars

Author

Watters, Thomas R., Leuschen, Carl J., Plaut, Jeffrey J., Picardi, Giovanni, Safaeinili, Ali, Clifford, Stephen M., Farrell, William M., Ivanov, Anton B., Phillips, Roger J., and Stofan, Ellen R.

Subjects
Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Author(s): Thomas R. Watters (corresponding author) [1]; Carl J. Leuschen [2]; Jeffrey J. Plaut [3]; Giovanni Picardi [4]; Ali Safaeinili [3]; Stephen M. Clifford [5]; William M. Farrell [6]; Anton [...]

Published
2006
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15. Mars chronology: assessing techniques for quantifying surficial processes

Author

Doran, Peter T., Clifford, Stephen M., Forman, Steven L., Nyquist, Larry, Papanastassiou, Dimitri A., Stewart, Brian W., Sturchio, Neil C., Swindle, Timothy D., Cerling, Thure, Kargel, Jeff, McDonald, Gene, Nishiizumi, Kunihiko, Poreda, Robert, Rice, James W., and Tanaka, Ken

Subjects
Rock mechanics -- Discovery and exploration, Mars (Planet) -- Discovery and exploration, Earth sciences
Abstract

Currently, the absolute chronology of Martian rocks, deposits and events is based mainly on crater counting and remains highly imprecise with epoch boundary uncertainties in excess of 2 billion years. Answers to key questions concerning the comparative origin and evolution of Mars and Earth will not be forthcoming without a rigid Martian chronology, enabling the construction of a time scale comparable to Earth's. Priorities for exploration include calibration of the cratering rate, dating major volcanic and fluvial events and establishing chronology of the polar layered deposits. If extinct and/or extant life is discovered, the chronology of the biosphere will be of paramount importance. Many radiometric and cosmogenic techniques applicable on Earth and the Moon will apply to Mars after certain baselines (e.g. composition of the atmosphere, trace species, chemical and physical characteristics of Martian dust) are established. The high radiation regime may pose a problem for dosimetry-based techniques (e.g. luminescence). The unique isotopic composition of nitrogen in the Martian atmosphere may permit a Mars-specific chronometer for tracing the time-evolution of the atmosphere and of lithic phases with trapped atmospheric gases. Other Mars-specific chronometers include measurement of gas fluxes and accumulation of platinuqa group elements (PGE) in the regolith. Putting collected samples into geologic context is deemed essential, as is using-multiple techniques on multiple samples. If in situ measurements are restricted to a single technique it must be shown to give consistent results on multiple samples, but in all cases, using two or more techniques (e.g. on the same lander) will reduce error. While there is no question that returned samples will yield the best ages, in situ techniques have the potential to be flown on multiple missions providing a larger data set and broader context in which to place the more accurate dates. Keywords: Mars; Chronology: Surficial processes; Dating

Published
2004

16. The evolution of the Martian hydrosphere: implications for the fate of a primordial ocean and the current state of the northern plains

Author

Clifford, Stephen M. and Parker, Timothy J.

Subjects
Mars (Planet) -- Surface, Water -- Research, Cryosphere, Astronomy, Earth sciences
Abstract

In this paper we consider the hydraulic and thermal conditions that gave rise to the elevated source regions of the Late Hesperian outflow channels and explore their implications for the evolution of the Martian hydrosphere. We find that if the outflow channel floodwaters were derived from a subpermafrost aquifer, then it implies that, throughout the planet's first billion years of evolution, as much as one third of its surface was covered by standing bodies of water and ice. Following the development of the global dichotomy, the bulk of this water would have existed as an ice-covered ocean in the northern plains. We demonstrate that the progressive crustal assimilation of this early surface reservoir of [H.sub.2]O (punctuated by possible episodes of less extensive flooding) was a natural consequence of the planet's subsequent climatic and geothermal evolution--potentially cycling the equivalent of a km-deep global ocean of water through the atmosphere and subsurface every ~[10.sup.9] years. In response to the long-term decline in planetary heat flow, the progressive cold-trapping of [H.sub.2]O into the growing cryosphere is expected to have significantly depleted the original inventory of groundwater--a development that could well explain the apparent decline in outflow channel activity observed during the Amazonian. Although primarily a theoretical analysis, our findings appear remarkably consistent with the geomorphic and topographic evidence that Mars once possessed a primordial ocean and that a substantial relic of that body continues to survive as massive ice deposits within the northern plains. Confirmation of the presence of such deposits, combined with the potential detection of a global-scale groundwater system, would provide persuasive support for the validity of this analysis. Key Words: Mars, surface; Mars, atmosphere; Mars, climate; ices; exobiology.

Published
2001

19. Supply services of English armed forces, 1509-50

Author

Davies, Clifford Stephen Lloyd

Subjects
900, Great Britain--Armed Forces--Procurement--History--16th century, Great Britain--Armed Forces--Supplies and stores--History--16th century
Abstract

This thesis attempts to trace the effect of the increased size and complexity of armies and navies in the early VIth Century on the English supply services, and also to analyse selected campaigns as a test of governmental efficiency. The provision of ships, guns, gunpowder, and hand-weapons is first discussed, in relation to national self-sufficiency. Ship timber was occasionally imported, but England could, if necessary, have done without foreign supplies; the timber problem was not a pressing one at this period. Naval stores (pitch, cordage etc.) on the other hand, were almost always imported, and the Baltic had thus already acquired something of its later strategic importance. Equally important were the Netherlands. In 1509 all but the smallest artillery was obtained there. This was remedied by the beginning of large-scale bronze and cast-iron gun-manufacture in England; but England still depended on the Netherlands in 1550 for saltpetre (for gunpowder) and copper (for bronze). Werner Sombart's contention that military requirements stimulated the growth of large-scale industry is discussed; shipbuilding and cannon-founding support his argument, provided that the small-scale of industry in general at this period is borne in mind.

Published
1963

21. Genetic studies of western gorillas

Author

Clifford, Stephen L., primary, Abernethy, Kate A., additional, White, Lee J. T., additional, Tutin, Caroline E. G., additional, Bruford, Mike W., additional, and Wickings, E. Jean, additional

Published
2002
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23. The iceball next door

Author

Clifford, Stephen M.

Subjects
Mars (Planet) -- Environmental aspects -- Research -- Atmosphere, Astronomy, Research, Environmental aspects
Abstract

Several spacecraft are or will soon be scrutinizing Mars for reservoirs of water and ice that scientists strongly suspect lie hidden beneath the planet's surface. WHEN Mariner 4 returned the [...]

Published
2003

24. Initiation of Martian Outflow Channels: Related to the Dissociation of Gas Hydrate?

Author

Max, Michael D and Clifford, Stephen M

Subjects
Lunar And Planetary Science And Exploration
Abstract

We propose that the disruption of subpermafrost aquifers on Mars by the thermal- or pressure-induced dissociation of methane hydrate may have been a frequent trigger for initiating outflow channel activity. This possibility is raised by recent work that suggests that significant amounts of methane and gas hydrate may have been produced within and beneath the planet's cryosphere. On Earth, the build-up of overpressured water and gas by the decomposition of hydrate deposits has been implicated in the formation of large blowout features on the ocean floor. These features display a remarkable resemblance (in both morphology and scale) to the chaotic terrain found at the source of many Martian channels. The destabilization of hydrate can generate pressures sufficient to disrupt aquifers confined by up to 5 kilometers of frozen ground, while smaller discharges may result from the water produced by the decomposition of near-surface hydrate alone.

Published
2001
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25. The State, Potential Distribution, and Biological Implications of Methane in the Martian Crust

Author

Max, Michael D and Clifford, Stephen M

Subjects
Lunar And Planetary Science And Exploration
Abstract

The search for life on Mars has recently focused on its potential survival in deep (>2 km) subpermafrost aquifers where anaerobic bacteria, similar to those found in deep subsurface ecosystems on Earth, may have survived in an environment that has remained stable for billions of years. An anticipated by-product of this biological activity is methane. The detection of large deposits of methane gas and hydrate in the Martian cryosphere, or as emissions from deep fracture zones, would provide persuasive evidence of indigenous life and confirm the presence of a valuable in situ resource for use by future human explorers.

Published
2000
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26. The State and Future of Mars Polar Science and Exploration

Author

Clifford, Stephen M, Crisp, David, Fisher, David A, Herkenhoff, Ken E, Smrekar, Suzanne E, Thomas, Peter C, Wynn-Williams, David D, Zurek, Richard W, Barnes, Jeffrey R, and Bills, Bruce G

Subjects
Lunar And Planetary Science And Exploration
Abstract

As the planet's principal cold traps, the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of approx. 10(exp 6)sq km and total as much as 3-4 km thick. From the scarcity of superposed craters on their surface, these layered deposits are thought to he comparatively young-preserving a record of the seasonal and climatic cycling of atmospheric CO2, H2O, and dust over the past approx. 10(exp 5)-10(exp 8) years. For this reason, the martian polar deposits may serve as a Rosetta Stone for understanding the geologic and climatic history of the planet-documenting variations in insolation (due to quasiperiodic oscillations in the planet's obliquity and orbital elements), volatile mass balance, atmospheric composition, dust storm activity, volcanic eruptions, large impacts, catastrophic floods, solar luminosity, supernovae, and perhaps even a record of microbial life. Beyond their scientific value, the polar regions may soon prove important for another reason-providing a valuable and accessible reservoir of water to support the long-term human exploration of Mars. In this paper we assess the current state of Mars polar research, identify the key questions that motivate the exploration of the polar regions, discuss the extent to which current missions will address these questions, and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding.

Published
2000
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27. Complex phylogeographic history of central African forest elephants and its implications for taxonomy

Author

Curran Bryan, Nyakaana Silvester, Goossens Benoît, Clifford Stephen L, Johnson Mireille B, White Lee JT, Wickings E Jean, and Bruford Michael W

Subjects
Evolution, QH359-425
Abstract

Abstract Background Previous phylogenetic analyses of African elephants have included limited numbers of forest elephant samples. A large-scale assessment of mitochondrial DNA diversity in forest elephant populations here reveals a more complex evolutionary history in African elephants as a whole than two-taxon models assume. Results We analysed hypervariable region 1 of the mitochondrial control region for 71 new central African forest elephants and the mitochondrial cytochrome b gene from 28 new samples and compare these sequences to other African elephant data. We find that central African forest elephant populations fall into at least two lineages and that west African elephants (both forest and savannah) share their mitochondrial history almost exclusively with central African forest elephants. We also find that central African forest populations show lower genetic diversity than those in savannahs, and infer a recent population expansion. Conclusion Our data do not support the separation of African elephants into two evolutionary lineages. The demographic history of African elephants seems more complex, with a combination of multiple refugial mitochondrial lineages and recurrent hybridization among them rendering a simple forest/savannah elephant split inapplicable to modern African elephant populations.

Published
2007
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28. Modeling Tsunami Propagation and the Emplacement of Thumbprint Terrain in an Early Mars Ocean: TSUNAMIS ON MARS

Author

Costard, François, Séjourné, Antoine, Kelfoun, Karim, Clifford, Stephen, Lavigne, Franck, Di Pietro, Ilaria, Bouley, Sylvain, Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Magmas et Volcans (LMV), Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet [Saint-Étienne] (UJM)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Institute [Houston] (LPI), Laboratoire de géographie physique : Environnements Quaternaires et Actuels (LGP), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Université Panthéon-Sorbonne (UP1), International Research School of Planetary Sciences [Pescara] (IRSPS), and Università degli studi 'G. d'Annunzio' Chieti-Pescara [Chieti-Pescara] (Ud'A)

Subjects
[SDE]Environmental Sciences, [SHS]Humanities and Social Sciences
Published
2017

29. A model for the hydrologic and climatic behavior of water on Mars

Author

Clifford, Stephen M

Subjects
Lunar And Planetary Exploration
Abstract

An analysis is carried out of the hydrologic response of a water-rich Mars to climate change and to the physical and thermal evolution of its crust, with particular attention given to the potential role of the subsurface transport, assuming that the current models of insolation-driven change describe reasonably the atmospheric leg of the planet's long-term hydrologic cycle. Among the items considered are the thermal and hydrologic properties of the crust, the potential distribution of ground ice and ground water, the stability and replenishment of equatorial ground ice, basal melting and the polar mass balance, the thermal evolution of the early cryosphere, the recharge of the valley networks and outflow, and several processes that are likely to drive the large-scale vertical and horizontal transport of H2O within the crust. The results lead to the conclusion that subsurface transport has likely played an important role in the geomorphic evolution of the Martian surface and the long-term cycling of H2O between the atmosphere, polar caps, and near-surface crust.

Published
1993

30. The seismic response of an aquifer to the propagation of an impact generated shock wave: A possible trigger of the Martian outflow channels?

Author

Leyva, Ivett A and Clifford, Stephen M

Subjects
Lunar And Planetary Exploration
Abstract

Aquifer dilation from shock waves produced by the 8.4 magnitude Alaskan earthquake of 1964 led to water and sediment ejection from the ground up to 400 km away from the earthquake's epicenter. Groundwater disturbances were observed as far away as Perry, Florida (approximately 5500 km), where well water fluctuations with an amplitude of as much as 2.3 m were reported. The martian cratering record provides evidence that the planet has experienced numerous seismic events of a similar, and often much greater, magnitude. Given this fact, and the photogeologic evidence for abundant water in the early crust, the response of a basalt aquifer to the propagation of compressional waves (P-waves) produced by impacts in the 33-1000 km diameter size range were investigated. The resulting one-dimensional changes in effective stress and pore pressure were calculated - as a function of both distance and time - based on the following assumptions: (1) that all of the seismic energy radiated by an impact is transmitted as a single compressional wave; (2) that both the host rock and groundwater are compressible; and (3) that there is no net flow between the water-filled pores.

Published
1993

31. The role of the geothermal gradient in the emplacement and replenishment of ground ice on Mars

Author

Clifford, Stephen M

Subjects
Lunar And Planetary Exploration
Abstract

Knowledge of the mechanisms by which ground ice is emplaced, removed, and potentially replenished, are critical to understanding the climatic and hydrologic behavior of water on Mars, as well as the morphologic evolution of its surface. Because of the strong temperature dependence of the saturated vapor pressure of H2O, the atmospheric emplacement or replenishment of ground ice is prohibited below the depth at which crustal temperatures begin to monotonically increase due to geothermal heating. In contrast, the emplacement and replenishment of ground ice from reservoirs of H2O residing deep within the crust can occur by at least three different thermally-driven processes, involving all three phases of water. In this regard, Clifford has discussed how the presence of a geothermal gradient as small as 15 K/km can give rise to a corresponding vapor pressure gradient sufficient to drive the vertical transport of 1 km of water from a reservoir of ground water at depth to the base of the cryosphere every 10(exp 6) - 10(exp 7) years. This abstract expands on this earlier treatment by considering the influence of thermal gradients on the transport of H2O at temperatures below the freezing point.

Published
1993

32. Mars: The initial emplacement of ground ice in response to the thermal evolution of its early crust

Author

Clifford, Stephen M

Subjects
Lunar And Planetary Exploration
Abstract

Given the geomorphic evidence for the widespread occurrence of water and ice in the early martian crust, and the difficulty involved in accounting for this distribution given the present climate, it has been suggested that the planet's early climate was originally more Earth-like, permitting the global emplacement of crustal H2O by direct precipitation as snow or rain. The resemblance of the martian valley networks to terrestrial runoff channels, and their almost exclusive occurrence in the planet's ancient (approximately 4 billion year old) heavily cratered terrain, is often cited as evidence of just such a period. An alternative school of thought suggests that the early climate did not differ substantially from that of today. Advocates of this view find no compelling reason to invoke a warmer, wetter period to explain the origin of the valley networks. Rather, they cite evidence that the primary mechanism of valley formation was ground water sapping, a process that does not require that surface water exist in equilibrium with the atmosphere. However, while sapping may successfully explain the origin of the small valleys, it fails to address how the crust was initially charged with ice as the climate evolved towards its present state. Therefore, given the uncertainty regarding the environmental conditions that prevailed on early Mars, the initial emplacement of ground ice is considered from two perspectives: (1) that the early climate started warm and wet, but gradually cooled with time; and (2) that it never differed substantially from that of today.

Published
1993

33. The thermodynamic case for a water-rich Mars

Author

Clifford, Stephen M

Subjects
Lunar And Planetary Exploration
Abstract

The geologic evidence for a water-rich Mars has been reviewed, and it has been concluded that it is consistent with an outgassed inventory of H2O equivalent to global ocean 0.5-1 km deep. The most persuasive support for this conclusion comes from the martian outflow channels, whose distribution, size, and range of ages, suggests that a significant body of ground water was present on Mars throughout much of its geologic history. In this abstract, the thermodynamic implications of the outflow channels are considered. The results of this analysis suggest that if the outflow channels were carved by the discharge of ground water in diffusive and thermodynamic equilibrium with the overlying frozen crust, it implies a minimum planetary inventory of water in excess of 300 m. However, if the global inventory of ground water on Mars at the time of outflow channel formation was as high as the 500 m estimate of other researchers, then the total inventory of water on Mars could well exceed 750 m.

Published
1993

34. The role of thermal vapor diffusion in the subsurface hydrologic evolution of Mars

Author

Clifford, Stephen M

Subjects
Lunar And Planetary Exploration
Abstract

The hydrologic response of groundwater to the thermal evolution of the early martian crust is considered. When a temperature gradient is present in a moist porous medium, it gives rise to a vapor-pressure gradient that drives the diffusion of water vapor from regions of high to low temperature. By this process, a geothermal gradient as small as 15 K/km could drive the vertical transport of 1 km of water to the freezing front at the base of the martian crysophere every 10 exp 6-10 exp 7 years, or the equivalent of about 100-1000 km of water over the course of martian geologic history. Models of the thermal history of Mars suggest that this thermally-driven vapor flux may have been as much as 3-5 times greater in the past. The magnitude of this transport suggests that the process of geothermally-induced vapor diffusion may have played a critical role in the initial emplacement of ground ice and the subsequent geomorphic and geochemical evolution of the martian crust.

Published
1991

35. Shrinkage and hardness of dental composites acquired with different curing light sources.

Author

Clifford, Stephen S., Roman-Alicea, Karla, Tantbirojn, Daranee, and Versluis, Antheunis

Subjects
OPERATIVE dentistry, LIGHT emitting diodes, LIGHT sources, POLYMERS, COMPOSITE materials, DENTAL materials
Abstract

Objectives: Curing light sources propel the photopolymerization process. The effect of 3 curing units on polymerization shrinkage and depth of cure was investigated. Method and Materials: The curing lights were a conventional and a soft-start quartz-tungstenhalogen (QTH) light source and a light-emitting diode (LED) source. The soft-start QTH and LED intensity outputs were 9% and 17% less than the conventional QTH source, respectively. For a 40-second light cure, the light energy was 32% and 14% lower, respectively. The light sources were applied to 4 restorative composites (microfilled, 2 hybrids, and nanofilled). For each light unit-composite combination, the development of postgel shrinkage during polymerization was measured with strain gauges (n = 15), and the Knoop hardness was tested at 0.5-mm-depth increments to assess degree of cure 15 minutes after polymerization (n = 5). The results were statistically analyzed with 2-way ANOVA at .05 significance level, followed by pairwise comparisons. Results: Both factors, light source and composite, significantly affected postgel shrinkage and hardness (P < .05). The conventional QTH unit generally produced the highest shrinkage and hardness (at composite surface and 2-mm depth). The soft-start QTH unit generated the least shrinkage but achieved the lowest depth of cure. The resulting values for the LED unit were mostly in between the results of the other 2 units. Conclusion: Curing lights should provide sufficient light energy to thoroughly cure composite restorations, which might be achieved without compromising shrinkage stresses if initial intensity is reduced. [ABSTRACT FROM AUTHOR]

Published
2009

36. Dielectric map of the Martian northern hemisphere and the nature of plain filling materials

Author

Mouginot, Jeremie, Pommerol, Antoine, Beck, Pierre, Kofman, Wlodek, and Clifford, Stephen M.

Abstract

A number of observations suggest that an extended ocean once covered a significant part of the Martian northern hemisphere. By probing the physical properties of the subsurface to unprecedented depth the MARSIS/Mars Express provides new geophysical evidences for the former existence of a Late Hesperian ocean. The Vastitas Borealis formation located inside a putative shoreline of the ancient ocean has a low dielectric constant compared with that of typical volcanic materials. We show that the measured value is only consistent with low density sedimentary deposits massive deposits of ground ice or a combination of the two. In contrast radar observations indicate a distribution of shallow ground ice in equilibrium with the atmosphere in the south polar region. We conclude that the northern plains are filled with remnants of a late Hesperian ocean fed by water and sediments from the outflow channels about 3 Gy ago. Citation: Mouginot J. A. Pommerol P. Beck W. Kofman and S. M. Clifford (2012) Dielectric map of the Martian northern hemisphere and the nature of plain filling materials Geophys. Res. Lett. 39 L02202 doi:10.1029/2011GL050286.

Published
2012

38. A steelworker solution: when all else failed they bought the shop

Author

Clifford, Stephen

Subjects
Shenango Group Inc. -- Mergers, acquisitions and divestments, Employee ownership -- Case studies, Steel industry -- Pennsylvania -- Mergers, acquisitions and divestments -- Case studies, Employee committees -- Case studies, Political science, Company acquisition/merger, Case studies, Mergers, acquisitions and divestments
Abstract

The Shenango Valley, which hugs the border between Ohio and Pennsylvania, is perhaps most famous for Shenango Lake. According to Trailer Life magazine, 'If you're interested in bragging-size crappies, Shenango [...]

Published
1995

39. Investigation of an alpine ice cave in Austria with the EXOMARS WISDOM GPR

Author

Ciarletti, Valérie, Clifford, Stephen, Plettemeier, Dirk, Dorizon, Sophie, Statz, Christoph, Lustrement, Benjamin, Humeau, Olivier, Hassen-Khodja, Rafik, Galic, Alexandre, Cais, Ph., ESTER - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), PLANETO - LATMOS, Lunar and Planetary Institute [Houston] (LPI), Technische Universität Dresden = Dresden University of Technology (TU Dresden), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), FORMATION STELLAIRE 2013, Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Cardon, Catherine

Subjects
[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, [INFO.INFO-TS] Computer Science [cs]/Signal and Image Processing, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [PHYS.ASTR.IM] Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, [SPI.SIGNAL] Engineering Sciences [physics]/Signal and Image processing, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; The WISDOM (Water Ice Subsurface Deposit Observations on Mars) Ground Penetrating Radar (GPR) is among the instruments selected as part of ESA's 2018 ExoMars Rover mission, whose scientific objectives are to search for signs of past and present life and to investigate the planet's subsurface. Combined with the rover, the GPR will provide high resolution observations of the structure of the shallow subsurface and assist in the identification and location of sedimentary layers or massive ice deposits, where organic molecules are the most likely to be found and well-preserved. The resulting data sets will also be a valuable tool for determining the nature, location and extent of potential targets for drilling. WISDOM prototypes, representative of the final flight model, are currently being field tested in various Mars analogue and cold-climate environments. In April 2012, members of the WISDOM team brought two development prototypes to an Alpine ice cave in Dachstein, Austria, to field test the instrument and participate in the Mars Simulation organized by the Austrian Space Forum. The GPRs were tested on 3 different platforms including the radio-controlled "Magma White" Rover from ABM Space Education in Poland. Radar investigations were conducted in four different cave environments, measuring ice thickness, stratigraphy, fracture geometry, and basal topography. Data sets processed and analyzed prove to be in agreement with the shallow environment characteristics determined by direct observation and previously obtained with commercial GPRs. From a geoelectrical point of view, massive ice containing a small amount of impurities can be approximate as a rather homogeneous medium. A massive ice unit will appear on a radargram as an area with no noticeable signal return, due to the little backscattered signal. Ice is also a low conductivity medium which leads to a deep penetration of the electromagnetic waves. The radargrams obtained from WISDOM data are consistent with those features. Deep and strong reflections can be observed from single scattered embedded in the ice or from interfaces below the ice unit. The wave velocity and thus the depth and the real permittivity values can be retrieved using individual reflectors' signature (hyperbolic shape) or the estimated reflection coefficient in case of a flat and smooth interface between a known material (air for example) and ice. Because of variations in fracture width, density and orientation, determining fracture geometry is the most challenging task among the retrieval of the other characteristics. The radar-derived 2- and 3-D reconstructions of the internal characteristics of the ice deposits and cave floor seem yet to be consistent with the observations. Additional field investigations, conducted in a wide variety of simulated and natural cold environments, are planned to build a database of well-characterized ice-rich terrestrial environments and improve our ability to characterize them. A more detailed discussion of these field results is currently in preparation.

Published
2013

40. Sounding the Ganymede's crust with a GPR

Author

Ciarletti, Valérie, Le Gall, Alice, Biancheri-Astier, Marc, Berthelier, Jean-Jacques, Clifford, Stephen, Plettemeier, Dirk, Cardon, Catherine, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Interactions et dynamique des environnements de surface (IDES), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Technische Universität Dresden = Dresden University of Technology (TU Dresden)

Subjects
[PHYS.ASTR.EP] Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]
Published
2013

41. Detecting and characterizing ice units with the WISDOM Radar

Author

Ciarletti, Valérie, Plettemeier, Dirk, Dorizon, Sophie, Clifford, Stephen M., Biancheri-Astier, Marc, Dechambre, Monique, Saintenoy, Albane, Costard, F., PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ESTER - LATMOS, Technische Universität Dresden = Dresden University of Technology (TU Dresden), Lunar and Planetary Institute [Houston] (LPI), Interactions et dynamique des environnements de surface (IDES), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Cardon, Catherine

Subjects
[PHYS.ASTR.EP] Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]
Abstract

The WISDOM (Water Ice Subsurface Deposit Observation on Mars) Ground Penetrating Radar (GPR) is one of the instruments that have been selected as part of the Pasteur payload of ESA's 2018 ExoMars Rover mission. WISDOM main objectives are to understand the geology and evolution of the landing site and to help identifying locations in the shallow subsurface where organic molecules are the most likely to be found and well-preserved. In the context of the ExoMars mission, the importance of the WISDOM GPR is particularly enhanced by its ability to investigate the distribution and state of subsurface water - both as a liquid and as ice. For example, within the diurnally active thermal layer of the subsurface (i.e., the top ~15 - 25 cm), the transient melting and freezing of subsurface ice and brine may be detectable by comparing day- and night-time radar observations at the same location. Moreover, while the biological significance of liquid water on Mars is obvious, a more readily accessible and enduring record of biological activity may be organic biomarkers preserved in subsurface ice. Unfortunately, the dielectric contrast between rock, soil and ice is small, and therefore, differentiating between mixtures of ice-rich and ice-poor regolith in the Martian subsurface is an extraordinarily difficult task. Preliminary tests in both natural (glacier in the Alps and caves in Austria) and artificial (cold chamber) icy environments have been performed with a prototype representative of the WISDOM instrument flight model. These investigations have demonstrated WISDOM's ability to detect and characterize subsurface ice in various forms. Specific examples will be discussed that demonstrate the instrument's depth of sounding, dielectric sensitivity, spatial resolution, full polarimetric and 3-D capability.

Published
2012

42. The NetStation GPR: A Tool for Conducting Lander-Based 3-D Investigations of Martian Subsurface Structure, Stratigraphy, and Volatile Distribution

Author

Ciarletti, Valérie, Clifford, Stephen M., Plettemeier, Dirk, Le Gall, Alice, Biancheri-Astier, Marc, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Institute [Houston] (LPI), Technische Universität Dresden = Dresden University of Technology (TU Dresden), and Cardon, Catherine

Subjects
[PHYS.ASTR.EP] Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]
Abstract

The NetStation GPR is a stationary, impulse, multiband polarimentric HF GPR, designed to conduct geologic and volatile-related investigations of the Martian near- and deep-subsurface (~10 m - 1 km).

Published
2012

43. Fully Polarimetric Ground Penetrating Radar WISDOM

Author

Plettemeier, Dirk, Ciarletti, Valérie, Cais, Ph., Benedix, Wolf-Stefan, Statz, Christophe, Clifford, Stephen, Hamran, Svein-Erik, Technische Universität Dresden = Dresden University of Technology (TU Dresden), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ESTER - LATMOS, FORMATION STELLAIRE 2011, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB), Lunar and Planetary Institute [Houston] (LPI), Norwegian Defence Research Establishment (FFI), Centre National d'Etudes Spatiales (CNES), German space agency (DLR), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB)

Subjects
[PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

International audience; The Ground Penetrating Radar (GPR) WISDOM is designed to be part of 2018 ExoMars Rover payload. The main scientific objective of WISDOM is to characterize the material distribution within the first few meters of the Martian subsurface and to search for evidence of past and present life on Mars. The WISDOM radar will provide a penetration depth of about 3 meters with a resolution of a few centimetres within the Martian soil. A preliminary "real time" subsurface analysis supports the drill operations in finding places of high scientific interest and low risk. The joint data interpretation together with the drill team will significantly support the radar calibration. This presentation will focus on instrument performance depending on the accommodation of the WIDOM antennas aboard a Mars rover. Preliminary tests in the lab and in the field have shown that apart from the electronic unit the fully polarimetric antenna arrangement is one key element for the localization and characterization of buried scatterers and for the construction of a three dimensional subsurface map of the shallow Martian ground.

Published
2011

44. Radar Sounding Investigations of the Martian Subsurface by the 2018 ExoMars-C Rover

Author

Ciarletti, Valérie, Plettemeier, Dirk, Cais, Ph., Clifford, Stephen, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), ESTER - LATMOS, Technische Universität Dresden = Dresden University of Technology (TU Dresden), FORMATION STELLAIRE 2011, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB), Lunar and Planetary Institute [Houston] (LPI), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB)

Subjects
[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR]
Abstract

International audience; The WISDOM (Water Ice Subsurface Deposit Observation on Mars) Ground Penetrating Radar will fly on the ESA-NASA 2018 ExoMars-C mission, which combines the science payload of the original ESA ExoMars Rover with the robotic arm and sample cache of NASA's Max-C Rover into a single rover, whose samples will ult imately be retrieved by a future Mars Sample Return mission. WISDOM was designed to investigate the nearsubsurface down to a depth of ~2-3 m, commensurate with the sampling capabilit ies of the rover's drill. The information provided by WISDOM will assist in understanding the large-scale geology and history of the landing site, as well as selecting the most appropriate locations where to drill and collect sub surface samples for further analysis. Here we review the real-world performance of the instrument as experimentally observed in various field test environments.

Published
2011

45. Properties of the 67P/Churyumov-Gerasimenko interior revealed by CONSERT radar

Author

Kofman, Wlodek, primary, Herique, Alain, additional, Barbin, Yves, additional, Barriot, Jean-Pierre, additional, Ciarletti, Valérie, additional, Clifford, Stephen, additional, Edenhofer, Peter, additional, Elachi, Charles, additional, Eyraud, Christelle, additional, Goutail, Jean-Pierre, additional, Heggy, Essam, additional, Jorda, Laurent, additional, Lasue, Jérémie, additional, Levasseur-Regourd, Anny-Chantal, additional, Nielsen, Erling, additional, Pasquero, Pierre, additional, Preusker, Frank, additional, Puget, Pascal, additional, Plettemeier, Dirk, additional, Rogez, Yves, additional, Sierks, Holger, additional, Statz, Christoph, additional, Svedhem, Hakan, additional, Williams, Iwan, additional, Zine, Sonia, additional, and Van Zyl, Jakob, additional

Published
2015
Full Text
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46. The WISDOM Radar: Unveiling the Subsurface Beneath the ExoMars Rover and Identifying the Best Locations for Drilling.

Author

Ciarletti, Valérie, Clifford, Stephen, Plettemeier, Dirk, Le Gall, Alice, Hervé, Yann, Dorizon, Sophie, Quantin-Nataf, Cathy, Benedix, Wolf-Stefan, Schwenzer, Susanne, Pettinelli, Elena, Heggy, Essam, Herique, Alain, Berthelier, Jean-Jacques, Kofman, Wlodek, Vago, Jorge L., and Hamran, Svein-Erik

Subjects
*ROVING vehicles (Astronautics), *MARTIAN exploration, *OXIDIZING agents, *SPACE biology
Abstract

The search for evidence of past or present life on Mars is the principal objective of the 2020 ESA-Roscosmos ExoMars Rover mission. If such evidence is to be found anywhere, it will most likely be in the subsurface, where organic molecules are shielded from the destructive effects of ionizing radiation and atmospheric oxidants. For this reason, the ExoMars Rover mission has been optimized to investigate the subsurface to identify, understand, and sample those locations where conditions for the preservation of evidence of past life are most likely to be found. The Water Ice Subsurface Deposit Observation on Mars (WISDOM) ground-penetrating radar has been designed to provide information about the nature of the shallow subsurface over depth ranging from 3 to 10 m (with a vertical resolution of up to 3 cm), depending on the dielectric properties of the regolith. This depth range is critical to understanding the geologic evolution stratigraphy and distribution and state of subsurface H2O, which provide important clues in the search for life and the identification of optimal drilling sites for investigation and sampling by the Rover's 2-m drill. WISDOM will help ensure the safety and success of drilling operations by identification of potential hazards that might interfere with retrieval of subsurface samples. Key Words: Ground penetrating radar-Martian shallow subsurface-ExoMars. Astrobiology 17, 565-584. [ABSTRACT FROM AUTHOR]

Published
2017
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