THE CHANGING GEOCHEMICAL ENVIRONMENT AT IUS CHASMA, MARS, AS DETERMINED THROUGH THE MINERALOGY AND STRATIGRAPHY OF AQUEOUS OUTCROPS

Ius Chasma is an intriguing site in western Valles Marineris on Mars that contains outcrops of sulfates, phyllosilicates, and a unique hydrated component. We are investigating the Geryon Montes section of Ius Chasma where these hydrated materials have been extensively detected. Our study focuses on analysis of spectral data collected by CRISM and coordinated views of the mineralogy from CRISM with higher resolution and stereo views from the HRSC, CTX, and HiRISE cameras. Early analysis of this site observed unique surface materials that could be attributed to acidic alteration [1]. The unique surface features include unusual spectral “doublet” features found in CRISM images that have two bands between 2.2 – 2.3 μm and our work discovered these are highly variable across this region. These spectra are unusual on Mars, where most phyllosilicate outcrops have either a single band near 2.2 μm or near 2.3 μm, but not both. Here we analyzed newly calibrated versions of CRISM images to further probe the mineralogy, including the components contributing to the spectral doublet features. Both MTRDR versions of CRISM images that include joined S and L image data and reduced spectral noise to provide improved spectra across the region 0.4 to 3.9 μm [2] and a new algorithm employing simultaneous atmospheric correction and denoising that results in superior spectra of the surface from 1 – 2.6 μm [3] were utilized. Spectra were compared from both methods, verifying the integrity of each processing method. Further, we employed a new feature extracting algorithm based on Generative Adversarial Networks [4] to identify locations that contain the “doublet” features. This study characterized the spectral doublet features identified at Ius Chasma, Mars in relation to mixtures of hydrated silica and phyllosilicates with sulfate minerals, including jarosite and gypsum, that could be forming through aqueous alteration of the wall rock. Characterizing the stratigraphy of these unique components in relation to the phyllosilicates and hydrated silica indicates changes in the geochemical environment over time.

[1] Roach L.H. et al. (2010) Icarus, 206, 253-268.

[2] Seelos F.P. et al. (2016) 47th LPSC, Abs. #1783.

[3] Itoh Y. & Parente M. (2021) Icarus, 354, 114024.

[4] Saranathan A.M. & Parente M. (2021) Icarus, 355, 114107.