Cathy Quantin

Fluvial and lacustrine activity on layered deposits in Melas Chasma, Valles Marineris, Mars

[1] Valley networks on Mars are the most obvious features attesting that different geologic processes and possibly climatic conditions existed in the past. THEMIS images reveal valley networks within Melas Chasma, in Valles Marineris, a Hesperian-age canyon system. The valley networks in Melas Chasma are dense and highly organized, and the heads of the valleys are scattered at different elevations. All these features suggest that the networks were fed by precipitation. The morphological details reveal inner channels on some valley floors, attesting that water flowed within these valleys. On the DEM, the valleys flow into a completely enclosed depression. The edge of this feature follows a MOLA contour line, and the depression shows many sedimentary morphologies suggesting lacustrine environment. These landforms are located on remnants of layered deposits possibly composed of sulfate layers suggesting that fluvial activity could have contributed to the erosion of the layered terrains in Valles Marineris. Collectively, the features in Melas Chasma are a maximum of Hesperian in age. These results suggest that warm, wet environmental conditions on Mars persisted through the Hesperian and were present during the formation of Valles Marineris. The evidence for a paleolake in Melas Chasma attests to adequate environmental conditions for life development through the Hesperian period.

Stratigraphic architectures spotted in southern Melas Chasma, Valles Marineris, Mars

The distribution in space and time of liquid water on Mars is a haunting question because of its relevance to astrobiology and astroclimatology. To date, most orbital observations which attest to past fluvial and lacustrine activity on Mars have been dedicated to surficial landforms (i.e., drainage networks and depositional fans). Here we report an unprecedented identification of typical stratigraphic architectures made in Mars Global Surveyor Mars Orbiter Camera images of layered material in southern Melas Chasma. A particular set of strata is arranged in three depositional sequences bounded by stratigraphic unconformities. The sequences show spectacular, steeply-inclined clinoforms, and a broad channel-like depression. There are the same complex stratal patterns in Valles Marineris on Mars as there are in terrestrial deposits. Insights into these three-dimensional deposit geometries are used to tentatively isolate specific depositional processes and point to ancient subaqueous settings. Findings in southern Melas mark out a very attractive spot to which the search for ancient habitable environments on Mars could be directed.

New insights on the runout of large landslides in the Valles‐Marineris canyons, Mars

[1] Analogy with lab-scale dry granular flow experiments demonstrates that runouts and deposits heights of Valles-Marineris (VM) landslides can be scaled on a curve varying primarily with the initial aspect ratio of the mobilized rock mass (before slope failure). This results suggests both that any interstitial fluid played a negligible part in the VM landslides dynamics and that mobility is not an appropriate tool to characterize their dynamics.

The adapted Modified Gaussian Model: A tool to characterize the composition of magmatic rocks on terrestrial ‘planets’

Here we present an adapted version of the Modified Gaussian Model (MGM), a tool developed to detect and characterize both simple and complex mineralogies in magmatic rocks, and we review the results we obtained over the last years on four different planetary bodies. We first describe the working principle of the adapted MGM technique, with the differences compared to the original version, and the validation process using various laboratory and natural spectra. We then describe the results obtained on the Oman ophiolite (Earth), taken as a planetary spectral analog for magmatic terrains. We finally present spectroscopy-based mineralogical maps and some petrologic implications for key regions of Mars, the Moon and asteroid (4) Vesta.

Data reduction of CRISM data to highlight alteration minerals

CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) hyperspectral data have a spatial resolution ranging from 12 to 36m/pixel allowing the high resolution mapping of minerals at the surface of Mars. However, the signal-to-noise ratio (SNR) makes challenging the discrimination of minerals spectrally close such as certain phyllosilicates and carbonates. Here, we discuss different processing of data reduction used to improve the signal-to-noise ratio and to highlight the alteration minerals at the surface of Mars and their limit. We show that our tool allows to understand trends in global mineralogy present in hyperspectral data cube.