Samples collected by Mars 2020 Perseverance at Jezero Crater for Mars Sample Return

Perseverance roverMars 2020 Perseverance rover is currently exploring Jezero Crater on Mars, which contains an ancient lake-delta fan system with a high potential for past habitability. One of Perseverance’s primary science goals is to collect a set of scientifically return-worthy samples for return to Earth (Mars Sample Return; MSR) [1]. Between February 2021 and May 2024, Perseverance has sealed 24 tubes containing 21 rock cores, 2 regolith samples and one atmosphere sample. Of the 17 rock cores and regolith samples, 8 were collected on the crater floor, 9 at the fan front, 3 at fan top and 3 at the Margin. Additionally, 3 witness tube assemblies (WTAs), which will serve as blanks for contamination control, have been sealed. A total of ten tubes have been deposited in a depot in the Three Forks area. All rock and regolith samples are accompanied by a set of observations (Sample Threshold Observation Protocol, the STOP List) performed on abrasion patches or regolith near each sample collection site. These observations are documented in the Initial Reports and the Sample Dossier which are available through the Geosciences Node of the Planetary Data System (https://pds-geosciences.wustl.edu). Samples The eight rock cores collected on the crater floor include samples of the two major rock units of the crater floor, the Máaz formation (basaltic to basaltic-andesite) and the Séitah formation (olivine-cumulate). In addition to the primary igneous mineralogy such as olivine, pyroxene and feldspar, these samples contain alteration minerals such as sulfates, carbonates and perchlorates indicating interaction with liquid water in the past [2]. These samples will be important for understanding Mars igneous history and providing constraints on the timing of Jezero crater and the fan units. The alteration phases in the rocks will enable studies of water-rock interaction within Jezero crater.The seven rock cores collected from the Shenandoah formation at the fan front are all fine-grained sedimentary rocks that were likely deposited in a lacustrine environment [3]. If returned to Earth, these rocks would be the first sedimentary rocks from Mars to be studied in terrestrial laboratories. Three cores (Hazeltop, Bearwallow and Kukaklek) were collected at the layered outcrops Wildcat Ridge and the stratigraphically equivalent Hidden Harbor. These samples are fine-grained sandstones to siltstones and are mainly composed of sulfates and phyllosilicates. They also contain various diagenetic features such as calcium sulfate veins/veinlets (typically anhydrite) and putative concretions. Two cores (Swift Run and Skyland) were collected at the layered outcrop Skinner Ridge. They are medium- to coarse- grained sandstones containing pyroxene, feldspar, carbonates and serpentine. Finally, two cores (Shuyak and Mageik) were collected at the layered outcrop Amalik. They are fine-grained sandstones and mainly composed of olivine grains that have been altered to phyllosilicates, most likely a serpentine phase. There are also carbonates associated with these cores. The phyllosilicates, sulfates and other alteration phases present in the fan front rock cores could potentially have trapped organic matter and other biosignatures originating from the ancient lake or from the Jezero watershed. Thus, these samples will be exceptionally valuable for astrobiological investigations upon return from Mars.The two regolith samples (Atmo mountain and Crosswind) were collected at a megaripple, Observation Mountain, near Amalik at the delta front [4]. The samples consist of different-sized grains of varying compositions including olivine, altered olivine, feldspar, carbonates, sulfates and phosphates. These samples will enable studies of the regolith and dust of Mars.Three cores were collected at the fan top, Melyn, Otis Peak and Pilot Mountain [5]. They are all poorly sorted medium sandstone with clasts ranging up to pebble sizes and believed to be part of the Tenby formation, which likely represents a fluvial environment and overlies the fan front. They contain olivine, feldspar, pyroxene and alteration phases such as Mg-Fe carbonates, Mg-sulfates, Ca-sulfates, phyllosilicates and chlorinated phases. These samples represent some of the coarsest sedimentary material yet sampled by the rover. Their detrital clasts have diverse lithologies likely sourced from the Nili Planum region outside Jezero crater that contains some of the oldest known rocks on Mars (>~4 billion years old). Therefore, laboratory investigations of these samples will enable the study of a source-to-sink sedimentary system on Mars that will inform how surface environments, aqueous processes, and habitability evolved through time, both within the catchment and the fan. Finally, three cores were collected in the Margin unit with two cores collected in the eastern Margin (Pelican Point and Lefroy Bay) and one core in the western Margin (Comet Geyser) [6]. They are all medium to coarse sandstones expect Comet Geyser which could be either a coarse sandstone or aqueously altered igneous rock. The rocks contain a high portion of carbonates with silica as a likely cement. Also present are olivine, pyroxene, minor feldspar, altered silicates and phyllosilicates. The Margin unit has a high astrobiological interest due to its high carbonate signal as observed from space and in-situ and its potential as a shoreline deposit. Parts of carbonates and silica are microcrystalline which make them excellent for biosignature preservation.Perseverance is currently continuing its exploration of the Margin unit with the possible collection of one more sample. After finishing the Margin campaign, the next step is to explore the crater rim which will include some of the oldest rocks on Mars (>~4 billion years old).[1] Farley K.A. et al. Space Science Reviews, 216 (2020), [2] Farley, K.A. et al. Science, 377 (2022), [3] Bosak et al. Lunar Planetary and Science Conference (2024), [4] Hausrath, E.M et al. Lunar Planetary and Science Conference (2023), [5] Weiss B. et al. Lunar Planetary and Science Conference (2024), [6] Siljeström et al. Lunar Planetary and Science Conference (2024)

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