T138 Lakes and Lake Deposits on Earth and Mars (Posters)

Monday, 28 October 2013
9:00 AM - 6:30 PM
Hall D

PAST WATER ACTIVITY IN ARIADNES COLLES

Paper number: T138-1
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Mars exhibits numerous 'chaotic terrains' typified by a jumble of mesas and knobs of varying sizes, though to have been formed by collapse. Ariadnes Colles, one of these chaotic terrains, is located in the southern highlands of Mars, in a circular depression with a maximum diameter of about 240 km, at about 34° south and 172° east. It covers an area of about 180 x 160 square km. We analyzed the topography, stratigraphy, morphology and mineralogy using MOLA, HRSC, CTX, MOC and HiRISE imagery together with hyperspectral data from CRISM. These have been atmospherically and photometrically corrected via the CAT tool v7.0 under the ENVI software. They have been used to identify the mineralogical composition of the knobs. We localize the spectra with the diagnostic signatures of phyllosilicates and sulfates, then we divided them by neutral spectra extracted from the same data cubes to reduce noise and emphasize the absorption bands in the spectra.

The floor is characterized by mesas and knobs that are about 1 to 10 km, generally larger the central than in the outer part of the chaos. The knobs mesas typically contain light-toned materials that display numerous fractures filled by light material. Both phyllosilicates and sulfates are recognized in the light toned materials indicating formation in both a water-rich environment and an evaporative environment. The light-toned materials are often covered by a darker rubbly layer interpreted to be lava flows. These morphologies could be the remainder of previously more extended materials, which are more resistant to erosion probably due to a process of cementation by fluid circulation and/or a more resistant capping layer. The presence of dendritic valley networks near the rims of the basin, that run towards its center (for example near 173°E - 38°N) and which confirm past water activity and suggest Ariadnes may have probably hosted a lake, consistent with previous interpretations of a lake in this region. Phyllosilicates record sustained weathering perhaps associated with the valley networks; sulfates may represent periods of evaporation within the lake lifetime.