¹E.M.Hausrath et al. (>10)
Journal of Geophysical research (Planets) Link to Article [https://doi.org/10.1029/2022JE007433]
¹Department of Geoscience, University of Nevada, Las Vegas, Nevada, 89154 USA
Published by arrangement with John Wiley & Sons

Martian soils are critically important for understanding the history of Mars, past potentially habitable environments, returned samples, and future human exploration. This paper examines soil crusts on the floor of Jezero crater encountered during initial phases of the Mars 2020 mission. Soil surface crusts have been observed on Mars at other locations, starting with the two Viking Lander missions. Rover observations show that soil crusts are also common across the floor of Jezero crater, revealed in 45 of 101 locations where rover wheels disturbed the soil surface, 2 out of 7 helicopter flights that crossed the wheel tracks, and 4 of 8 abrasion/drilling sites. Most soils measured by the SuperCam laser-induced breakdown spectroscopy (LIBS) instrument show high hydrogen content at the surface, and fine-grained soils also show a visible/near infrared (VISIR) 1.9 µm H2O absorption feature. The Planetary Instrument for X-ray Lithochemistry (PIXL) and SuperCam observations suggest the presence of salts at the surface of rocks and soils. The correlation of S and Cl contents with H contents in SuperCam LIBS measurements suggests that the salts present are likely hydrated. On the “Naltsos” target, magnesium and sulfur are correlated in PIXL measurements, and Mg is tightly correlated with H at the SuperCam points, suggesting hydrated Mg-sulfates. Mars Environmental Dynamics Analyzer (MEDA) observations indicate possible frost events and potential changes in the hydration of Mg-sulfate salts. Jezero crater soil crusts may therefore form by salts that are hydrated by changes in relative humidity and frost events, cementing the soil surface together.

¹A.Udry et al. (>10)
Journal Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2022JE007440]
¹Department of Geosciences, University of Nevada Las Vegas, Las Vegas, NV, US
Published by arrangement with John Wiley & Sons

The Máaz formation consists of the first lithologies in Jezero crater analyzed by the Mars 2020 Perseverance rover. This formation, investigated from Sols (martian days) 1 to 201 and from Sols 343 to 382, overlies the Séítah formation (previously described as an olivine-rich cumulate) and was initially suggested to represent an igneous crater floor unit based on orbital analyses. Using SuperCam data, we conducted a detailed textural, chemical, and mineralogical analyses of the Máaz formation and the Content member of the Séítah formation. We conclude that the Máaz formation and the Content member are igneous and consist of different lava flows and/or possibly pyroclastic flows with complex textures, including vesicular and non-vesicular rocks with different grain sizes. The Máaz formation rocks exhibit some of the lowest Mg# (=molar 100×MgO/MgO+FeO) of all martian igneous rocks analyzed so far (including meteorites and surface rocks) and show similar basaltic to basaltic-andesitic compositions. Their mineralogy is dominated by Fe-rich augite to possibly ferrosilite and plagioclase, and minor phases such as Fe-Ti oxides and Si-rich phases. They show a broad diversity of both compositions and textures when compared to martian meteorites and other surface rocks. The different Máaz and Content lava or pyroclastic flows all originate from the same parental magma and/or the same magmatic system, but are not petrogenetically linked to the Séítah formation. The study of returned Máaz samples in Earth-based laboratories will help constrain the formation of these rocks, calibrate martian crater counting, and overall, improve our understanding of magmatism on Mars.