Carbonate Detection With SuperCam in Igneous Rocks on the Floor of Jezero Crater, Mars

Abstract

Perseverance explored two geological units on the floor of Jezero Crater over the first 420 Martian days of the Mars2020 mission. These units, the Máaz and Séítah formations, are interpreted to be igneous in origin, with traces of alteration. We report the detection of carbonate phases along the rover traverse based on laser-induced breakdown spectroscopy (LIBS), infrared reflectance spectroscopy (IRS), and time-resolved Raman (TRR) spectroscopy by the SuperCam instrument. Carbonates are identified through direct detection of vibrational modes of CO 3 functional groups (IRS and TRR), major oxides content, and ratios of C and O signal intensities (LIBS). In Séítah, the carbonates are consistent with magnesite-siderite solid solutions (Mg# of 0.42-0.70) with low calcium contents (<5 wt.% CaO). They are detected together with olivine in IRS and TRR spectra. LIBS and IRS also indicate a spatial association of the carbonates with clays. Carbonates in Máaz are detected in fewer points, as: (a) siderite (Mg# as low as 0.03); (b) carbonate-containing coatings, enriched in Mg (Mg# ∼0.82) and spatially associated with different salts. Overall, using conservative criteria, carbonate detections are rare in LIBS (∼30/2,000 points), IRS (∼15/2,000 points), and TRR (1/150 points) data. This is best explained by (a) a low carbonate content overall, (b) small carbonate grains mixed with other phases, (c) intrinsic complexity of in situ measurements. This is consistent with orbital observations of Jezero crater, and similar to compositions of carbonates previously reported in Martian meteorites. This suggests a limited carbonation of Jezero rocks by locally equilibrated fluids. Plain Language SummaryCarbonates are mineral phases that generally form by alteration of primary, magmatic minerals. This alteration process may occur under a variety of environmental conditions, which affect the resulting carbonate phase: its abundance, composition, spatial distribution and the mineral phases it is associated with. Consequently, carbonates keep track of the environmental conditions under which they formed, and in particular, the amount of CO 2 and liquid water involved in their formation. Understanding the history of both water and CO 2 on Mars is critical to better understand the evolution of the red planet and its atmosphere, but also the origin of the water on Earth, and possibly the origin of life. Since the beginning of the Mars2020 mission in Jezero Crater, the SuperCam instrument has analyzed more than 200 rocks of the crater CLAVÉ ET AL.

Reflectance of Jezero Crater Floor: 1. Data Processing and Calibration of the Infrared Spectrometer (IRS) on SuperCam

“…Moreover, its quantification indicates an areal carbonate abundance of less than 20%, which is consistent with IR modal mineralogy (Poulet et al., 2022). These carbonate detections by IRS are also consistent with LIBS and Raman results (Clave et al., 2022).…”

“… Correlation between the band depth‐to‐noise ratio (BDNR) of the 2.30 and 2.53 μm features for all the observations of the Crater Floor Campaign (black dots). Green points correspond to the phyllosilicate/carbonate mixtures detections confirmed by laser induced breakdown spectroscopy spectroscopy (Clave et al., 2022) and brown points are the targets from the Máaz unit. Arrows represent the 2.53/2.30 μm trend (in green for carbonate‐rich points in Séítah, in yellow for the Calcite SuperCam Calibration Target (SCCT) observations and in dark gray for the Séítah's negative detections) and are compared to lab reference magnesite/nontronite mixtures (in gray, Mag = magnesite, Non = nontronite).…”

Overview and Results From the Mars 2020 Perseverance Rover's First Science Campaign on the Jezero Crater Floor

“…Other possible explanations are that it was simply the fractures that did not experience extended interaction with fluids, or that the fractures postdate the period of alteration. The lack of observed fracture fill is consistent with the general observation that although alteration minerals are detected all along the traverse, the crater floor rocks are overall not substantially altered and large domains of the primary igneous lithology, especially olivine, are still preserved (Clavé et al, 2023;Liu et al, 2022;Tice et al, 2022).…”

“…The Bastide member is the more prevalent member, and is characterized by rocks that often appear layered (at various scales from the centimeter scale up to the decimeter scale; Figures 15 and 16), and are rich in olivine, some of which has been altered to carbonate (Clavé et al., 2023; Liu et al., 2022; Scheller et al., 2022). Despite the prevalence of layering in many Séítah outcrops, this layering was difficult to trace consistently across different outcrops.…”

“…However, these alteration events likely occurred at low temperatures, low water‐to‐rock ratios, and likely not in an extensive open system (Farley et al., 2022). The carbonates and Fe/Mg phyllosilicates detected in the Séítah and Máaz formations, respectively, were all detected at low proportions (a few weight percent; Mandon et al., 2023), and occurred with amorphous or poorly crystalline phases (Clavé et al., 2023; Scheller et al., 2022; Tice et al., 2022). Much of the original igneous minerals remain intact in both the Máaz and Séítah abrasions, and no Al‐phyllosilicates were detected, whose presence would have indicated that alteration occurred in an open system where soluble species like Ca, Na, K would be removed, leaving the rocks enriched in Al (Farley et al., 2022).…”