Evidence for Alteration and Diagenesis at Gale Crater, Mars from the Curiosity Rover
Abstract
The Mars Science Laboratory Curiosity rover landed in Gale crater in August 2012 and has been investigating the sedimentology, mineralogy, and geochemistry of lacustrine mudstone, fluvial and deltaic sandstone and conglomerate, and eolian sandstone emplaced 3.5 Ga. Mineralogical and geochemical data from Curiosity demonstrate aqueous alteration was prevalent (though not necessarily advanced) in ancient Gale crater, but without samples in hand it can be difficult to constrain whether the alteration was syn- or post-depositional (i.e., diagenetic). There is clear morphological and geochemical evidence for diagenesis by groundwater in Gale crater. Abundant concretions and Ca-sulfate veins throughout the traverse and subaqueous shrinkage cracks at Yellowknife Bay are indicative of groundwater. Fracture-associated halos in lacustrine mudstone and eolian sandstone are enriched in amorphous silica and depleted in crystalline phases compared to the host rock, and geochemical data suggest groundwater mobilized Mg, Al, Mn, Fe, Ni, and Zn. Other mineralogical and geochemical data are consistent with aqueous alteration, but this alteration may have occurred in lake waters, groundwater, or the sediment source region. Smectite is found in nearly all lacustrine mudstone samples drilled to date, and we hypothesize that much of it formed while the lakes were present. Compositional and structural changes in smectite within the stratigraphy, however, suggest that the sediments up-section were more intensely weathered in a near-surface environment. Magnetite and/or hematite are found in all rock and soil samples, and could be an important cementing agent. Magnetite is prevalent down-section, whereas hematite is more abundant up-section, suggesting lake and/or groundwater became more oxidizing over time. Abundant Ca-sulfate up-section in the sedimentary matrix may have also formed from diagenesis. A lack of advanced weathering products suggests diagenetic reactions at Gale crater are under-developed compared to Earth.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P43A..01R
- Keywords:
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- 0406 Astrobiology and extraterrestrial materials;
- BIOGEOSCIENCESDE: 6225 Mars;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5415 Erosion and weathering;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5419 Hydrology and fluvial processes;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 0406 Astrobiology and extraterrestrial materials;
- BIOGEOSCIENCESDE: 6225 Mars;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5415 Erosion and weathering;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5419 Hydrology and fluvial processes;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS