The first samples collected by the Perseverance rover on the Mars 2020 mission were from the Maaz formation, a lava plain that covers most of the floor of Jezero crater. Laboratory analysis of these samples back on Earth will provide important constraints on the petrologic history, aqueous processes, and timing of key events in Jezero. However, interpreting these samples will require a detailed understanding of the emplacement and modification history of the Maaz formation. Here we synthesize rover and orbital remote sensing data to link outcrop-scale interpretations to the broader history of the crater, including Mastcam-Z mosaics and multispectral images, SuperCam chemistry and reflectance point spectra, RIMFAX ground penetrating radar, and orbital hyperspectral reflectance and high-resolution images. We show that the Maaz formation is composed of a series of distinct members corresponding to basaltic to basaltic andesite lava flows. The members exhibit variable spectral signatures dominated by high-Ca pyroxene, Fe-bearing feldspar, and hematite, which can be tied directly to igneous grains and altered matrix in abrasion patches. Spectral variations correlate with morphological variations, from recessive layers that produce a regolith lag in lower Maaz, to weathered polygonally fractured paleosurfaces and crater-retaining massive blocky hummocks in upper Maaz. The Maaz members were likely separated by one or more extended periods of time, and were subjected to variable erosion, burial, exhumation, weathering, and tectonic modification. The two unique samples from the Maaz formation are representative of this diversity, and together will provide an important geochronological framework for the history of Jezero crater. Hosted fileessoar.10512674.1.docx available at https://authorea.com/users/531790/articles/620328mineralogy-morphology-and-emplacement-history-of-the-maaz-formation-on-the-jezerocrater-floor-from-orbital-and-rover-observations Mineralogy, morphology, and emplacement history of the Maaz formation on the Jezero crater floor from orbital and rover observations

Approach: The Mars Exploration Rover Spirit has experienced over 2000 martian days (sols) of interaction w ith the martian dust c ycle. Much d ust accumulated o n the vehicle, but there have also been t hree major "cleaning e vents" when s ignificant a mounts o f d ust w ere removed. Pa ncam d ust monitoring observations acquired every ~10 sols throughout the mission allowed visual inspection of the amount of dust collecting on a portion of the solar array and on the Pancam and Mini-TES calibration targets. Pancam multispectral d ata reveal three classes of airborne d ust adhering to the capture and filter magnets: 1) "bright" capture magnet dust 2) "dark" capture magnet dust, and 3) filter magnet dust. Microscopic Imager (MI) images of the capture and filter magnets and a portion of the solar array aid in interpretation of behavior and morphology of the dust deposits. Results: Three s ignificant periods of "cleaning e vents" removed s ubstantial a mounts o f d ust from the rover. Each event occurred during southern hemisphere early spring and summer, and occurred later i n the s eason of each s uccessive M artian y ear. Pancam m ultispectral d ata o f "bright" capture magnet d ust exhibit the h ighest r eflectance l evels of t he t hree cl asses. T hese sp ectra a re a lso characterized by steep visible spectral slopes (434 to 673 nm), strong 535 nm absorptions, and are relatively featureless and c onvex in shape i n the NIR region. "Dark" capture magnet dust has the lowest reflectance levels of the three classes, much shallower visible slopes and are much less "red" than the bright capture dust. They also have shallower 535 nm absorptions and are featureless in the NIR. They exhibit positive slopes from 900 to 1000 nm. Filter magnet dust shares spectral characteristics with the "dark" capture magnet dust, and together they represent a darker, more strongly magnetic component. Both Pancam and MI images reveal that the dust particles on the rover b ody cohere an d f orm larger ag gregates, measured at 100 µm to several m m. MI i mages of the rover magnets and body show that grains collected range from assumed (unresolved) dust size (< 4 µm) to fine sand (250 µm), and show that sand can saltate to a rover deck height of 70 cm in strong w inds. T hrough c omparisons with o ther d ata s ets and previous work, w e think w ind speeds exceeding 20 m/s are responsible for the removal of dust during the cleaning events. Implications: The spectral characteristics of the "bright" capture dust described here are consistent with multispectral observations of dust and bright soil elsewhere on the martian surface and support the theory that martian dust is globally mixed and deposited. This expanded data set also provides further e vidence that the d ust has a d arker, more s trongly magnetic component than typical b right dust. The large size of observed dust aggregates (≥ 100 µm) should make them easier to entrain by wind than individual dust grains, and therefore represent another process by which dust is lifted into the at...

The first samples collected by the Perseverance rover on the Mars 2020 mission were from the Maaz formation, a lava plain that covers most of the floor of Jezero crater. Laboratory analysis of these samples back on Earth would provide important constraints on the petrologic history, aqueous processes, and timing of key events in Jezero crater. However, interpreting these samples requires a detailed understanding of the emplacement and modification history of the Maaz formation. Here we synthesize rover and orbital remote sensing data to link outcrop‐scale interpretations to the broader history of the crater, including Mastcam‐Z mosaics and multispectral images, SuperCam chemistry and reflectance point spectra, RIMFAX ground penetrating radar, and orbital hyperspectral reflectance and high‐resolution images. We show that the Maaz formation is composed of a series of distinct members corresponding to basaltic to basaltic‐andesite lava flows. The members exhibit variable spectral signatures dominated by high‐Ca pyroxene, Fe‐bearing feldspar, and hematite, which can be tied directly to igneous grains and altered matrix in abrasion patches. Spectral variations correlate with morphological variations, from recessive layers that produce a regolith lag in lower Maaz, to weathered polygonally fractured paleosurfaces and crater‐retaining massive blocky hummocks in upper Maaz. The Maaz members were likely separated by one or more extended periods of time, and were subjected to variable erosion, burial, exhumation, weathering, and tectonic modification. The two unique samples from the Maaz formation are representative of this diversity, and together will provide an important geochronological framework for the history of Jezero crater.

Perseverance’s Mastcam-Z instrument provides high-resolution stereo and multispectral images with a unique combination of spatial resolution, spatial coverage, and wavelength coverage along the rover’s traverse in Jezero crater, Mars. Images reveal rocks consistent with an igneous (including volcanic and/or volcaniclastic) and/or impactite origin and limited aqueous alteration, including polygonally fractured rocks with weathered coatings; massive boulder-forming bedrock consisting of mafic silicates, ferric oxides, and/or iron-bearing alteration minerals; and coarsely layered outcrops dominated by olivine. Pyroxene dominates the iron-bearing mineralogy in the fine-grained regolith, while olivine dominates the coarse-grained regolith. Solar and atmospheric imaging observations show significant intra- and intersol variations in dust optical depth and water ice clouds, as well as unique examples of boundary layer vortex action from both natural (dust devil) and Ingenuity helicopter–induced dust lifting. High-resolution stereo imaging also provides geologic context for rover operations, other instrument observations, and sample selection, characterization, and confirmation.

NASA’s Mars‐2020 Perseverance rover spent its first year in Jezero crater studying the mafic lava flows of the Máaz formation and the ultramafic cumulates of the Séítah formation, both of which have undergone minor alteration and are variably covered by coatings, dust and/or soil deposits. Documenting the rock and soil characteristics across the crater floor is critical for establishing the geologic context of Perseverance’s cached samples – which will eventually be returned to Earth – and for interpreting the deposition and modification of the Máaz and Séítah formations. Mastcam‐Z, a pair of multispectral, stereoscopic zoom‐lens cameras, provides broadband red/green/blue and narrowband visible to near‐infrared images (VNIR, 440‐1020 nm). From multipsectral observations from sols 0‐380, we compiled a database of ∼2400 representative Mastcam‐Z spectra. We analyzed principal components, spectral parameters and laboratory spectra of pure minerals and natural rock surfaces to interpret the spectral diversity of rocks and soils. We define eight spectral classes of rocks: Dusty, Hematite‐like, Coated, Low‐Ca Pyroxene‐like, Olivine‐like, Weathered Olivine‐like, Fe‐rich Pyroxene‐like, and Dark Oxide‐like. The variability of soil spectra in the Jezero crater floor is controlled primarily by the amount of dust and indicates a largely consistent soil mineralogy across the traverse, with the exception of the area disturbed by the landing event. In comparison to rock spectra from the Curiosity rover’s Mastcam instrument in Gale crater, rocks on the Jezero crater floor are generally less spectrally diverse, but the Olivine‐like rocks within the Séítah formation represent new spectral classes in Mars surface exploration.