We have studied the properties of the Nili Fossae olivine lithology from orbital data and in situ by the Mars 2020 rover at the Séítah unit in Jezero crater. We used the geochemistry collected by the rover’s instruments to calculate the viscosity and relative flow distance of the Séítah unit. Based on the low viscosity and distribution of the unit we postulate a ponded lava flow origin for the olivine rich unit at Séítah. We calculate an approximate depth for the cumulate layer of the lava pond based on the viscosity of the unit and model of Worster et al. (1993). We show that the resolution of orbital data is inadequate to map the phyllosilicate 2.38 μm band and demonstrate that it can be supplemented by in situ data from Mars 2020 SuperCam Laser Induced Breakdown Spectroscopy (LIBS) and reflectance observations to show that the low Al phyllosilicate in the olivine cumulate in the Séítah formation is either talc, serpentine, hectorite, Fe/Mg smectite, saponite or stevensite. We discuss two intertwining aspects of the history of the lithology: 1) the potential emplacement and properties of the cumulate layer within a ponded lava flow, using previously published models of ponded lava flows and lava lakes, and 2) the limited extent of post emplacement alteration, including phyllosilicate and carbonate alteration.

We have studied the observed properties of the Nili Fossae olivine-phyllosilicate-carbonate lithology from orbital data and in situ by the Mars 2020 rover at the Séítah unit in Jezero crater, including: 1) composition 2) grain size 3) inferred viscosity (calculated based on geochemistry collected by SuperCam (Wiens et al., 2022)). Based on the low viscosity and distribution of the unit we postulate a flood lava origin for the olivine-phyllosilicate-carbonate at Séítah. We include a new CRISM map of the phyllosilicate 2.38 μm band and use in situ data from Mars 2020 SuperCam Laser Induced Breakdown Spectroscopy (LIBS) and VISIR and MastCam-Z observations to show that the phyllosilicate in the olivine cumulate in the Séítah formation is either talc, serpentine, hectorite, Fe/Mg smectite, saponite or stevensite. We discuss two intertwining aspects of the history of the lithology: 1) the emplacement and properties of the cumulate layer within a lava lake, based on terrestrial analogs in the Pilbara, Western Australia, and using previously published models of flood lavas and lava lakes, and 2) the limited extent of post emplacement alteration, including phyllosilicate and carbonate alteration.

We examine the observed properties of the Nili Fossae olivine-clay-carbonate lithology from orbital data and in situ by the Mars 2020 rover at the Séítah unit in Jezero crater, including: 1) composition (Liu, 2022) 2) grain size (Tice, 2022) 3) inferred viscosity (calculated based on geochemistry collected by SuperCam (Wiens, 2022)). Based on the low viscosity and distribution of the unit we postulate a flood lava origin for the olivine-clay-carbonate at Séítah. We include a new CRISM map of the clay 2.38 μm band and use in situ data to show that the clay in the olivine cumulate in the Séítah formation is consistent with talc or serpentine from Mars 2020 SuperCam LIBS and VISIR and MastCam-Z observations. We discuss two intertwining aspects of the history of the lithology: 1) the emplacement and properties of the cumulate layer within a lava lake, based on terrestrial analogs in the Pilbara, Western Australia, and using previously published models of flood lavas and lava lakes, and 2) the limited extent of post emplacement alteration, including clay and carbonate alteration (Clave, this issue; Mandon, this issue).