Presentation #100.04 in the session “Mars”.
On February 18, 2021, the Perseverance rover touched down ~2 km SE of the 40-m-high cliffs of the prominent western fan — now recognized as a delta — that attracted the mission to the crater’s open-system paleolake setting. In pursuit of its central objective to select, collect, and document samples for possible Earth return by a future mission, Perseverance is now intensively investigating rocks of the crater floor. Rocks at the landing site include flat-lying light-toned polygonal-shaped outcrops that commonly transition into darker, heavily ventifacted higher standing rocks. This unit, termed Crater Floor Fractured Rough, comprises the heavily cratered terrain east of the landing site. These rocks have a broadly mafic composition, clear evidence of hydration, are dusty, and have a purplish mottling that suggests a chemical coating; definitive lithologic characterization (e.g., igneous vs sedimentary) awaits the rover’s abrading capability and proximity science investigation in midsummer. Long-distance imagery of the western delta front and associated erosional remnants reveals several stages of fluvio-deltaic deposition, including a period of delta progradation and a later period of substantial fluvial flooding at lower lake level. Lying between the landing site and the delta is a remarkable region of SW-NE aligned ~5 to ~15 m high bedrock ridges with abundant sand dunes and boulders. These ridges contain outcrop of layered beds of few to few 10s of cm thickness, possibly fluvio-lacustrine or airfall ash deposits. This region, informally “Séítah”, is not traversable by the rover and prevents a straight-line drive to the delta. A testable working model of these units suggests multiple periods of lake filling, desiccation, and erosion; Séítah may be the oldest and the delta units the youngest deposits.
The rover is now traversing south along the edge of Séítah, gaining further data on the origin of both the flat-lying polygonal outcrop, and the layered rock within Séítah. The current mission plan includes coring of the polygonal unit, a brief foray into Séítah to collect probably two core samples of layered bedrock, and possibly collection of a fourth sample from a prominent set of raised ridges if they indicate post-depositional fluid flow and mineralization. Perseverance has also been characterizing the atmospheric environment of Jezero crater, with initial results revealing significant variability on daily and seasonal timescales, and frequent dust-lifting events.