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- Title
Petrological Traverse of the Olivine Cumulate Séítah Formation at Jezero Crater, Mars: A Perspective From SuperCam Onboard Perseverance.
- Authors
Beyssac, O.; Forni, O.; Cousin, A.; Udry, A.; Kah, L. C.; Mandon, L.; Clavé, O. E.; Liu, Y.; Poulet, F.; Quantin Nataf, C.; Gasnault, O.; Johnson, J. R.; Benzerara, K.; Beck, P.; Dehouck, E.; Mangold, N.; Alvarez Llamas, C.; Anderson, R. B.; Arana, G.; Barnes, R.
- Abstract
Séítah is the stratigraphically lowest formation visited by Perseverance in the Jezero crater floor. We present the data obtained by SuperCam: texture by imagery, chemistry by Laser‐Induced Breakdown Spectroscopy, and mineralogy by Supercam Visible and Infrared reflectance and Raman spectroscopy. The Séítah formation consists of igneous, weakly altered rocks dominated by millimeter‐sized grains of olivine with the presence of low‐Ca and high‐Ca pyroxenes, and other primary minerals (e.g., plagioclase, Cr‐Fe‐Ti oxides, phosphates). Along a ∼140 m long section in Séítah, SuperCam analyses showed evidence of geochemical and mineralogical variations, from the contact with the overlying Máaz formation, going deeper in the formation. Bulk rock and olivine Mg#, grain size, olivine content increase gradually further from the contact. Along the section, olivine Mg# is not in equilibrium with the bulk rock Mg#, indicating local olivine accumulation. These observations are consistent with Séítah being the deep ultramafic member of a cumulate series derived from the fractional crystallization and slow cooling of the parent magma at depth. Possible magmatic processes and exhumation mechanisms of Séítah are discussed. Séítah rocks show some affinity with some rocks at Gusev crater, and with some Martian meteorites suggesting that such rocks are not rare on the surface of Mars. Séítah is part of the Nili Fossae regional olivine‐carbonate unit observed from orbit. Future exploration of Perseverance on the rim and outside of the crater will help determine if the observations from the crater floor can be extrapolated to the whole unit or if this unit is composed of distinct sub‐units with various origins. Plain Language Summary: The Mars 2020 Perseverance rover landed on Mars in the Jezero crater on 18 February 2021. An important goal of this mission is to constrain the geology of the Jezero crater and its delta, and to sample rocks to return to Earth. Here, we study the deepest rock formation observed close to the landing site on the crater floor, named the Séitah formation. We conclude that this formation is igneous with rocks consisting in the accumulation of dominant millimeter‐sized olivine crystals with pyroxenes and other minerals. Such rocks form at depth by slow cooling of the magma, and the first mineral to crystallize (olivine) settles down by gravity in the magma. Such rocks bear similarity to other Martian rocks found in the Gusev crater by the Opportunity rover, and also to some Martian meteorites. These rocks will be studied in Earth‐based laboratories and will allow us to better understand magmatic processes on Mars. Key Points: The Séítah formation consists of an olivine cumulate series, weakly altered, preserving the igneous texture and mineralogyEmplacement of the Séítah formation required fractional crystallization and slow cooling of the parent magma at depth and erosionThe Séítah formation could be a particular member of the Nili Fossae regional olivine‐carbonate unit observed from orbit
- Subjects
OLIVINE; LUNAR craters; NEAR infrared reflectance spectroscopy; MARTIAN meteorites; LASER-induced breakdown spectroscopy; MARTIAN craters; IMPACT craters
- Publication
Journal of Geophysical Research. Planets, 2023, Vol 128, Issue 7, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2022JE007638