Search

A multi-instrument study of the regolith of Jezero crater floor units by the Perseverance rover has identified three types of regolith: fine-grained, coarse-grained, and mixed-type. Mastcam-Z, Wide Angle Topographic Sensor for Operations and eNgineering, and SuperCam Remote Micro Imager were used to characterize the regolith texture, particle size, and roundedness where possible. Mastcam-Z multispectral and SuperCam laser-induced breakdown spectroscopy data were used to constrain the composition of the regolith types. Fine-grained regolith is found surrounding bedrock and boulders, comprising bedforms, and accumulating on top of rocks in erosional depressions. Spectral and chemical data show it is compositionally consistent with pyroxene and a ferric-oxide phase. Coarse-grained regolith consists of 1-2 mm well-sorted gray grains that are found concentrated around the base of boulders and bedrock, and armoring bedforms. Its chemistry and spectra indicate it is olivine-bearing, and its spatial distribution and roundedness indicate it has been transported, likely by saltation-induced creep. Coarse grains share similarities with the olivine grains observed in the S & eacute;& iacute;tah formation bedrock, making that unit a possible source for these grains. Mixed-type regolith contains fine-and coarse-grained regolith components and larger rock fragments. The rock fragments are texturally and spectrally similar to bedrock within the M & aacute;az and S & eacute;& iacute;tah formations, indicating origins by erosion from those units, although they could also be a lag deposit from erosion of an overlying unit. The fine and coarse-grained types are compared to their counterparts at other landing sites to inform global, regional, and local inputs to regolith formation within Jezero crater. The regolith characterization presented here informs the regolith sampling efforts underway by Perseverance.Plain Language Summary We used multiple instruments on the Perseverance rover to describe three populations of loose sediments found on the floor of Jezero crater by their grain sizes and chemical compositions. The smallest population has grains that are small sand-sized (80-530 mu m) and a mixture of minerals commonly found on Mars, including pyroxene that is present in local rocks and airborne dust found globally. These grains are the easiest to move by wind, so could have distal regional sources as well. Larger gray grains that are 1-2 mm in size and rounded contain olivine. These grains move along the surface, pushed by the impacts of smaller grains that are lifted by the wind. Their size and composition are very similar to olivine grains found in nearby in-place rocks, indicating that they may have a more local source. Finally, there are larger pieces of rocks that have broken down from the erosion of local in-place rocks over time and mix with the other types of grains. Loose sediments within the Jezero crater described here can be compared to loose sediments studied at other landing sites on Mars to help understand how Jezero sediments are formed and transported.

On February 18, 2021, NASA’s Mars 2020 Perseverance rover landed successfully in Jezero crater. Several geological and compositional units were previously identified from orbital data analysis : a dark pyroxene-bearing floor unit; an olivine-bearing unit exposed in erosional windows and partially altered into phyllosilicates and carbonates ; a deltaic complex and its possible erosional remnants and a marginal carbonate-bearing unit. As of Sol 300 (December 2021), the rover has visited two geological units in situ: the dark pyroxene-bearing floor unit and the olivine-bearing floor unit. Others investigations of geological units of interest have been carried out using long distance (up to several kilometers) observations.The SuperCam instrument contains a suite of techniques including passive spectroscopy in the 0.40-0.85 (VIS) and 1.3-2.6 microns (IR) wavelength ranges, and a color camera (RMI- Remote Micro-Imager) providing high resolution context images. Since the landing, SuperCam has acquired thousands of VISIR spectra of nearby rocks (including both natural and abraded surfaces), as well as hundreds of spectra of distant targets (from 10s of m to 20 km). The VISIR field of view of each individual spectrum ranges from a few mm for the rock of the workspace to 20 m to 20 km. The aim of this contribution is to summarize the main results of VISIR spectra up to Sol 300.The two geological units investigated in situ have distinct spectra. The crater floor rough unit (Cf-fr) has a pervasive 1.9 µm absorption indicative of hydration. Additional absorption at 2.28 µm indicate the presence of iron-rich phyllosilicates. Correlations between 1.9 µm and 2.4 µm absorption bands or between 2.1 µm and 2.4 µm bands suggest the presence of both poly and monohydrated sulfates. Spectra similar to oxy-hydroxides have also been observed in some rocks. Unmixing methods such as factor analyses highlight a high calcium pyroxene component. To sum up, the Cf-fr is an altered pyroxene rich unit. The second unit investigated in situ is a region called Seitah, which is dominantly olivine-rich from orbital analyses. Supercam VISIR data confirm the strong signature of olivine of the unit and display a complex suite of absorptions in the 2.3 µm - 2.4 µm region suggesting the presence of iron and magnesium phyllosilicates and/or carbonates. The alteration signature seems to be associated with olivine grains. Distant observations were acquired on the western delta front, several remote mesas and hills, on Jezero floor unit (the unit on which Perseverance landed on and investigated in situ), on Seitah before being visited by the rover, and on even more distant targets such as the crater rim or the marginal carbonate-bearing unit. The observed spectral signatures form different clusters depending on the type of target, highlighting the spectral diversity of Jezero geological units. Remarkably, the long distance observations of Seitah region are in perfect agreement with the in situ measurements confirming the relevance of long distance observations to assess the geological/mineralogical context of Perseverance’s future traverses.

International audience; Orbital and rover observations of relictgeomorphic features and stratigraphic architectures indicate Mars once had a warmer, wetter climate. Constraining the character, relative timing and persistence of ancient aqueous activity on Mars is possible through detailed interrogation of the stratal geometry of aqueously deposited sedimentary bodies. Such analyses inform interpretations of Martian climate evolution, potential habitability, and search strategies for rocks that might contain potential biosignatures. A prominent sedimentary fan deposit at the westernmargin of Jezero crater has been inferred to be a river delta that built into an ancient lake basin during the Late Noachian-Early Hesperian epochs on Mars (~3.6-3.8 Ga) [1, 2, 3]. The Perseverance rover landed on 18 February 2021 ~2.2 km from the western fan. During the early phase of mission investigations, highresolution images obtained from the Mastcam-Z camera and from the Remote Micro-Imager of the SuperCaminstrument provided the first ground-based observations of the western fan and an associated remnant outcrop, named Kodiak. Here, we report its sedimentology, which provide new constraints on the nature of the fan deposits, and their paleoenvironmental implications (4).

On top of listening to laser shots, rover sounds and the Ingenuity rotorcraft, SuperCam’s Mars microphone has recorded over 7 hours of ambient background noise on Mars. These background recordings contain signal due to the Martian wind. Through a comparison to the meteorological data recorded by the MEDA (Mars Environmental Dynamics Analyzer), we can determine the relationships between the microphone data, the wind and the atmospheric stability. Based on these relationships, we have determined a way to estimate the wind speed using the microphone through Gaussian process regression, a machine learning technique. Owing to the sampling rate of 25 000 samples per second, the microphone data can be used to examine Mars’ atmospheric dynamics at high frequencies, as yet unexplored on Mars. We will demonstrate how the wind speed estimates from the microphone provide an assessment of turbulence at fine scales, shedding light on the dissipative regime on Mars. One particularly interesting signal recorded by the microphone was a dust devil, which had fast varying winds within the walls of its vortex and signal from dust particles hitting the rover. Combining the microphone data with information from the MEDA sensors and navigation camera (Navcam) images enabled a full parameterization of this event.