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Investigating the Diversity of Phyllosilicates and Sulfates at Mawrth Vallis, Mars and the Implications for Changing Environmental Conditions

Presentation #217.06 in the session Mars’ and Martian Moons’ Surface Properties and Composition (Oral Presentation)

Published onOct 23, 2023
Investigating the Diversity of Phyllosilicates and Sulfates at Mawrth Vallis, Mars and the Implications for Changing Environmental Conditions

Several new assemblages of phyllosilicates and sulfates have been discovered and mapped across Mawrth Vallis using improved algorithms for processing CRISM images. Fe/Mg-smectite is the most abundant component at this region, but smaller outcrops of other phyllosilicates and sulfates are also present. The newly available image cleaning [1] and mapping [2] techniques are enabling characterization of smaller deposits and weaker spectral signatures. Numerous outcrops containing alunite+kaolinite, allophane, halloysite, bassanite, gypsum+opal, jarosite, and polyhydrated sulfates (PHS) are observed at the tens of meters scale (or larger), often in between the transition from Fe/Mg-smectite to Al-rich phyllosilicates. The hydrated sulfates are most common in the channel and may have formed as evaporites or by brine percolating through the horizons. In contrast, the alunite and jarosite likely formed in acidic waters. Alunite commonly occurs as an assemblage with kaolinite or halloysite, and gypsum is commonly associated with opal or hydrated silica. Jarosite is more prevalent in the north and west of the Mawrth Vallis region and alunite-kaolinite-halloysite assemblages are more frequently observed in the south and east.

Previous analyses identified a common stratigraphy of five units composed of phyllosilicates and salty components [3] that extends across much of the Mawrth Vallis region. Here we present detections of unique outcrops of jarosite, alunite/kaolinite, Ca-sulfates, and PHS that occur in selected sites in between these phyllosilicate horizons, in the channel, or in depressions. We use knowledge of these mineral assemblages from analog environments and lab studies to provide models to explain formation of the observed mineral horizons across Mawrth Vallis and also the presence of the smaller, unique outcrops. Documenting these variations in the phyllosilicate and sulfate mineralogy at Mawrth Vallis is revealing the ancient geochemical environments and enabling us to place constrains on the ancient martian climate.

[1] Itoh Y. & M. Parente (2021) A new method for atmospheric correction and de-noising of CRISM hyperspectral data, Icarus, 354, 114024.

[2] Saranathan A. M. & M. Parente (2021) Adversarial feature learning for improved mineral mapping of CRISM data, Icarus, 355, 114107.

[3] Bishop J. L. et al. (2020) Multiple mineral horizons in layered outcrops at Mawrth Vallis, Mars, signify changing geochemical environments on early Mars. Icarus, 341, 113634.

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