Stratigraphy and formation of clays, sulfates, and hydrated silica within a depression in Coprates Catena, Mars

Abstract

We investigate the morphology, mineralogy, and stratigraphy of light‐toned layered deposits within a trough of Coprates Catena, centered at −15°N, 300°E. One of the deposits in the eastern portion of the trough contains numerous hydrated minerals, including Al‐phyllosilicates, Fe/Mg‐phyllosilicates, hydrated silica, hydrated sulfates, jarosite and acid alteration products characterized by a spectral doublet between 2.2 and 2.3 µm, and weakly hydrated materials. The Al‐phyllosilicates are observed both stratigraphically above and below the Fe/Mg‐phyllosilicate unit, which is a rare and perhaps unique association on Mars. Most of the western light‐toned layered deposit underlies a terraced fan. This deposit contains hydrated materials, including Al‐phyllosilicates and Fe/Mg‐phyllosilicates. Dip measurements indicate that both the eastern and western deposits dip toward the center of the trough, indicating that they postdate formation of the trough and are consequently Late Hesperian or younger in age. Volcanic ash, most likely erupted during formation of the pit crater in the eastern portion of the trough, seems to best explain our observations for several of the units. Valleys sourced from water along the plateau may have flowed into the trough and altered the sediments, with changing aqueous chemistries over time resulting in the diverse range of mineralogies now observed in the eastern light‐toned deposit. Our results reveal a complex sedimentary and aqueous history within the Coprates Catena trough, indicating that localized habitable conditions were possible relatively late in Martian history at a time when colder, drier conditions likely dominated the majority of the planet.

Episodic and Declining Fluvial Processes in Southwest Melas Chasma, Valles Marineris, Mars

“…Deposits of hydrated minerals (e.g., suites of clays and sulfates) are also found along the Valles Marineris plateaus (Le Deit et al, ; Weitz et al, ) and within the chasmata (e.g., Liu & Catalano, ; Murchie et al, ; Roach et al, ; Weitz et al, ). Fans interpreted to be alluvial and deltaic are found in Melas Chasma (e.g., Metz et al, ; Williams & Weitz, ) and Coprates Chasma, which also display a hydrated mineralogy (Grindrod et al, ; Weitz & Bishop, ). Hydrological modeling has predicted the emergence of regional groundwater throughout Valles Marineris (e.g., Andrews‐Hanna et al, ).…”

Evolution of major sedimentary mounds on Mars: Buildup via anticompensational stacking modulated by climate change

“…We excluded the well‐studied mounds Juventae Chasma [ Catling et al ., ; Bishop et al ., ] and Candor Mensa [ Mangold et al ., ; Fergason et al ., ; Fueten et al ., ]. (The criteria exclude a large number of sedimentary accumulations on Mars: e.g., plateau deposits [Mawrth, Loizeau et al ., ; Meridiani Planum, Hynek and Phillips , ; NE Arabia, Fassett and Head , ], the clay‐bearing Terby deposits [ Ansan et al ., ], the free‐standing Medusae Fossae mounds [ Bradley et al ., ; Burr et al , ; Zimbelman and Scheidt , ; Kite et al ., ], the NE Syrtis sulfate deposits [ Ehlmann and Mustard , ] and veneers and smaller mounds in and around VM [e.g., Milliken et al ., ; Thollot et al ., ; Weitz and Bishop , ].) Gale's mound (Aeolis Mons; also known as Mount Sharp) is the largest among 50 documented crater‐hosted mounds outside the polar regions [ Bennett and Bell , ], is the primary science target of Mars Science Laboratory (MSL) [ Mars Science Laboratory (MSL) Extended Mission Plan , ], and has the best HiRISE stereopair coverage of any within‐crater mound, justifying our emphasis on this within‐crater mound.…”

Widespread exposure of Noachian phyllosilicates in the Margaritifer region of Mars: Implications for paleohydrology and astrobiological detection

“…Likewise, surface weathering is not indicated, as this results in a succession comprising kaolinite, Al‐phyllosilicates, and Fe/Mg clays with depth, resulting from cation mobilization in order of solubility in downward percolating meteoric fluids [ Gaudin et al ., ]. Such sequences have been reported elsewhere on Mars and interpreted as evidence for pedogenesis [ Adeli et al ., ; Weitz and Bishop , ], but they are not seen in Margaritifer at CRISM resolution. Where LTBr has been exposed by surface erosion, these horizons could arguably have been removed, but where LTBr is exposed in scarps and retains its dark‐toned capping unit, any weathering succession can be expected to have been preserved.…”