302 research outputs found
Characterization and mapping of surface physical properties of Mars from CRISM multi-angular data: application to Gusev Crater and Meridiani Planum
The analysis of the surface texture from the particle (grain size, shape and
internal structure) to its organization (surface roughness) provides
information on the geological processes. CRISM multi-angular observations
(varied emission angles) allow to characterize the surface scattering behavior
which depends on the composition but also the material physical properties
(e.g., grain size, shape, internal structure, the surface roughness). After an
atmospheric correction by the Multi-angle Approach for Retrieval of the Surface
Reflectance from CRISM Observations, the surface reflectances at different
geometries are analyzed by inverting the Hapke photometric model depending on
the single scattering albedo, the 2-term phase function, the macroscopic
roughness and the 2-term opposition effects. Surface photometric maps are
created to observe the spatial variations of surface scattering properties as a
function of geological units at the CRISM spatial resolution (200m/pixel). An
application at the Mars Exploration Rover (MER) landing sites located at Gusev
Crater and Meridiani Planum where orbital and in situ observations are
available, is presented. Complementary orbital observations (e.g. CRISM
spectra, THermal EMission Imaging System, High Resolution Imaging Science
Experiment images) are used for interpreting the estimated Hapke photometric
parameters in terms of physical properties. The in situ observations are used
as ground truth to validate the interpretations. Varied scattering properties
are observed inside a CRISM observation (5x10km) suggesting that the surfaces
are controlled by local geological processes (e.g. volcanic resurfacing,
aeolian and impact processes) rather than regional or global. Consistent
results with the in situ observations are observed thus validating the approach
and the use of photometry for the characterization of Martian surface physical
properties
Formation of recurring slope lineae on Mars by rarefied gas-triggered granular flows
Active dark flows known as recurring slope lineae have been observed on the
warmest slopes of equatorial Mars. The morphology, composition and seasonality
of the lineae suggest a role of liquid water in their formation. However,
internal and atmospheric sources of water appear to be insufficient to sustain
the observed slope activity. Experimental evidence suggests that under the low
atmospheric pressure at the surface of Mars, gas can flow upwards through
porous Martian soil due to thermal creep under surface regions heated by the
Sun, and disturb small particles. Here we present numerical simulations to
demonstrate that such a dry process involving the pumping of rarefied gas in
the Martian soil due to temperature contrasts can explain the formation of the
recurring slope lineae. In our simulations, solar irradiation followed by
shadow significantly reduces the angle of repose due to the resulting temporary
temperature gradients over shaded terrain, and leads to flow at intermediate
slope angles. The simulated flow locations are consistent with observed
recurring slope lineae that initiate in rough and bouldered terrains with local
shadows over the soil. We suggest that this dry avalanche process can explain
the formation of the recurring slope lineae on Mars without requiring liquid
water or CO2 frost activity.Comment: 15 pages, 3 figure
Experimental Investigation of Gully Formation Under Low Pressure and Low Temperature Conditions
International audienceIntroduction: A large morphological diversity of gullies is observed on Earth and on Mars. Debris flow – a non-newtonian flow comprising a sediment-water mix – is a common process attributed to gully formation on both planets [1, 2]. Many variables can influence the morphology of debris flows (grainsizes, discharge , slope, soil moisture, etc) and their respective influences are difficult to disentangle in the field. Furthermore effects specific to the martian environment have not yet been explored in detail. Some preliminary laboratory simulations have already been performed that isolate some of these variables. Cold room experiments [3] were already perfomed to test the effect of a melted surface layer on the formation of linear gullies over sand dunes. Low pressure experiments [4] were performed to test the effect of the atmospheric pressure on erosional capacity and runout distance of the flows. Our aim is to develop a new set of experiments both under Martian atmospheric pressure and terrestrial atmospheric pressure in order to reproduce the variability of the observed morphologies under well constrained experimental conditions
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Orientation and distribution of recent gullies in the southern hemisphere of Mars: observations from HRSC/MEX and MOC/MGS data
Abstract not available
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Ice-Enriched Loess and the Formation of Periglacial Terrain in Mid-Utopia Planitia, Mars
Landforms suggestive of periglacial processes are commonplace in mid-Utopia Planitia, Mars. They form syngenetically in ground-ice comprised of loess transported by katabatic wind from the NPLDs and enriched by ice through the thaw-freeze cycling of obliquity-driven precipitation
Mars Analog Site Study (MASS)
Many proposed missions to Mars involve landing vehicles, including the Mars 94/96 (Russia), Mars Environmental Survey (MESUR, US), and the Marsnet (ESA) missions. Most landers involve in situ measurements of rock and soil compositions, study of local geology by imaging, and establishment of seismic and meteorological networks. The selection of landing sites on Mars is a complex process that must meet engineering constraints and scientific objectives, using available and anticipated data. The goal of the MASS project is to conduct an 'end-to-end' test of the site selection process using Earth analogs
Spatial relationships between patterned ground and ground ice detected by the neutron spectrometer on Mars
[1] Patterned grounds, like polygonal features, are the signature of climatic effects in periglacial regions on Earth. Identifying similar features on Mars is important for an understanding of the past Martian climate. In this study we mapped fresh patterned landforms from the systematic analysis of Mars Orbiter Camera high-resolution images. We show that most of them are distributed at latitudes poleward of ±55°, making a climatic control likely. This distribution correlates to the distribution of ground ice detected by the Neutron Spectrometer aboard Mars Odyssey. This correlation is likely the consequence of the Neutron Spectrometer detecting ice no deeper than about 1 m. Patterned ground formation requires ice in this range of depth because these features are triggered by the propagation of a thermal wave that is driven by seasonal or diurnal changes in insolation, which affect the temperature in the uppermost ground layers. Sublimation seems to play a role in the shaping of many of the small patterns observed at latitudes between 55°and 70°. No widespread polygonal features are correlated to the equatorial regions where hydrogen is detected by the Neutron Spectrometer
Gridmapping the northern plains of Mars: Geomorphological, Radar and Water-Equivalent Hydrogen results from Arcadia Plantia
A project of mapping ice-related landforms was undertaken to understand the role of sub-surface ice in the northern plains. This work is the first continuous regional mapping from CTX (“ConTeXt Camera”, 6 m/pixel; Malin et al., 2007) imagery in Arcadia Planitia along a strip 300 km across stretching from 30°N to 80°N centred on the 170° West line of longitude. The distribution and morphotypes of these landforms were used to understand the permafrost cryolithology. The mantled and textured signatures occur almost ubiquitously between 35° N and 78° N and have a positive spatial correlation with inferred ice stability based on thermal modelling, neutron spectroscopy and radar data. The degradational features into the LDM (Latitude Dependent Mantle) include pits, scallops and 100 m polygons and provide supporting evidence for sub-surface ice and volatile loss between 35-70° N in Arcadia with the mantle between 70-78° N appearing much more intact. Pitted terrain appears to be much more pervasive in Arcadia than in Acidalia and Utopia suggesting that the Arcadia study area had more wide-spread near-surface sub-surface ice, and thus was more susceptible to pitting, or that the ice was less well-buried by sediments. Correlations with ice stability models suggest that lack of pits north of 65-70° N could indicate a relatively young age (~1Ma), however this could also be explained through regional variations in degradation rates. The deposition of the LDM is consistent with an airfall hypothesis however there appears to be substantial evidence for fluvial processes in southern Arcadia with older, underlying processes being equally dominant with the LDM and degradation thereof in shaping the landscape
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