The geological units on the floor of Jezero crater, Mars, are part of a wider regional stratigraphy of olivine-rich rocks, which extends well beyond the crater. We investigate the petrology of olivine and carbonate-bearing rocks of the Séítah formation in the floor of Jezero. Using multispectral images and x-ray fluorescence data, acquired by the Perseverance rover, we performed a petrographic analysis of the Bastide and Brac outcrops within this unit. We find that these outcrops are composed of igneous rock, moderately altered by aqueous fluid. The igneous rocks are mainly made of coarse-grained olivine, similar to some Martian meteorites. We interpret them as an olivine cumulate, formed by settling and enrichment of olivine through multi-stage cooling of a thick magma body.

The Cassini Propulsion Module Subsystem (PMS) has performed excellently throughout the first four years of mission operations. The PMS is the most complex interplanetary propulsion subsystem ever flown, with separate monopropellant and bipropellant propulsion modules, each replete with many redundant components. Propulsion system performance has generally been exemplary, with the apparent exception of large leakage through the primary hard-seat regulator. Maneuver performance has been excellent, and the spacecraft has flown a complex, Venus-Venus-Earth-Jupiter gravity assist trajectory virtually trouble flee. There is no early evidence for pressure transducer drift, in contrast with the Galileo, Voyager, and TOPEX-Poseidon missions. PMS system health checks based on helium mass calculations (helium mass budgets) have demonstrated no discernible helium pressurant or propellant leakage to date. An extensive, in-flight assessment of 0.9-N monopropellant hydrazine thruster performance during pulse-mode operation has been undertaken. Main engine and hydrazine thruster performance has been within specification. Propellant and consumable usage have generally been lower than predicted, and the prospect for a highly successful, multi-year scientific investigation of the Saturnian system remains excellent.

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