Diverse Lava Flow Morphologies in the Stratigraphy of the Jezero Crater Floor

We present a combined geomorphologic, multispectral, and geochemical analysis of crater floor rocks in Jezero crater based on data obtained by the Mast Camera Zoom and SuperCam instruments onboard the NASA Mars 2020 Perseverance rover. The combined data from this analysis together with the results of a comparative study with geologic sites on Earth allows us to interpret the origins of rocks exposed along the Artuby ridge, a similar to 900 m long scarp of lower Maaz formation rocks. The ridge exposes rocks belonging to two morphologically distinct members, Artuby and Rochette, both of which have basaltic composition and are spectrally indistinguishable in our analysis. Artuby rocks consist of morphologically distinct units that alternate over the ridge, bulbous, hummocky, layers with varying thicknesses that in places appear to have flowed over underlying strata, and sub-planar thinner laterally continuous layers with variable friability. The Rochette member has a massive appearance with pronounced pitting and sub-horizontal partings. Our findings are most consistent with a primary igneous emplacement as lava flows, through multiple eruptions, and we propose that the thin layers result either from preferential weathering, interbedded ash/tephra layers, Modified Letter Turned CommaaModified Letter Turned Commaa clinker layers, or aeolian deposition. Our analyses provide essential geologic context for the Maaz formation samples that will be returned to Earth and highlight the diversity and complexity of geologic processes on Mars not visible from orbit. Plain Language Summary Characterization of the landing site for the Mars 2020 Perseverance rover mission yields insight into early solar system processes and provides essential context for Mars Sample Return. Here we have investigated crater floor rocks in Jezero crater that are exposed along a scarp called Artuby ridge with the Mast Camera Zoom (Mastcam-Z) and SuperCam instruments onboard the Perseverance rover. The Artuby ridge displays a characteristically layered set of rocks with a basaltic composition that are spectrally and chemically indistinguishable in our investigation. We compare our observations from Jezero with well-understood geologic deposits on Earth, from Hawai.i and New Mexico. We find that terrestrial lava flows can have complex interiors that replicate many features that we see in Mastcam-Z images of the Artuby ridge, and thus, that the series of rocks exposed along the Artuby ridge are dominated by lava flows originating through multiple eruptions. There are a number of layers and textures of the rocks in our investigation that may not have originated as lava flows, that instead may be products of weathering, interbedding of lava and volcanic ash/tephra, or wind-borne sediment deposition. Our results highlight the diversity of geologic units on Mars not visible from orbit.