¹E.Clave et al.(>10)
Journal of Geopyhsical Reearch (Planets)(in Press) Link to Article [https://doi.org/10.1029/2022JE007463]
¹CELIA, Université de Bordeaux, CNRS, CEA, Bordeaux, France
Published by arrangement with John Wiley & Sons

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 CO3 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: (i) siderite (Mg# as low as 0.03); (ii) 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 (∼30/2000 points), IRS (∼15/2000 points), and TRR (1 /150 points) data. This is best explained by (i) a low carbonate content overall, (ii) small carbonate grains mixed with other phases, (iii) 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.

¹L.Mandon et al. (>10)
Journal of Geopyhsical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2022JE007450]
¹LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, Meudon, France
Published by arrangement with John Wiley & Sons

The Perseverance rover landed in the ancient lakebed of Jezero crater, Mars on February 2021. Here we assess the mineralogy of the rocks, regolith, and dust measured during the first year of the mission on the crater floor, using the visible and near-infrared spectrometer of SuperCam onboard the Perseverance rover. Most of the minerals detected from orbit are present in the bedrock, with olivine-bearing rocks at the bottom of the stratigraphy and high-Ca pyroxene-bearing rocks at the top. This is distinct from the overall low-Ca pyroxene-bearing composition of the watershed of Jezero, and points towards an igneous origin. Alteration mineral phases were detected in most of the rocks analyzed in low proportions, suggesting that aqueous alteration of the crater floor has been spatially widespread, but limited in intensity and/or time. The diverse aqueous mineralogy suggests that the aqueous alteration history of the crater floor consists of at least two stages, to form phyllosilicates and oxyhydroxides, and later sulfates. We interpret their formation in a lake or under deeper serpentinization conditions, and in an evaporative environment, respectively. Spectral similarities of dust with some rock coatings suggest widespread past processes of dust induration under liquid water activity late in the history of Jezero. Analysis of the regolith revealed some local inputs from the surrounding rocks. Relevant to the Mars Sample Return mission, the spectral features exhibited by the rocks sampled on the crater floor are representative of the diversity of spectra measured on the geological units investigated by the rover.

¹Pei Ma,^1,2Hao Zhang,³Yazhou Yang,¹Te Jiang,⁴Daniel Britt,⁵Menghua Zhu
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115608]
¹School of Earth Sciences, China University of Geosciences, Wuhan, China
²CAS Center for Excellence in Comparative Planetology, Hefei, China
³National Space Science Center, Chinese Academy of Sciences, Beijing, China
⁴University of Central Florida, Orlando, FL, USA
⁵State Key Laboratory of Lunar and Planetary Science, Macau University of Science and Technology, Macau
Copyright Elsevier

As a new planetary remote sensing tool, the phase ratio imagery calculates the ratio of images taken at different phase angles and may suppress surface albedo variations and enhance surface texture features. This technique has been used in the study of surface structure of airless bodies such as the Moon and Mercury. To understand the effectiveness of the method, we carried out laboratory phase ratio measurements on eight planetary analog materials including four pure minerals olivine, orthopyroxene, labradorite, ilmenite and four mixtures, the lunar regolith simulant JSC-1A, the lunar highland simulant, the Martian soil simulant, and the CI asteroid simulant, all in two size distributions, 0–45 μm and 90–105 μm. For each sample, the phase ratio A(α1)/A(α2) is obtained by measuring the reflectance at two phase angles α1 and α2 with α1<α2 at two radiation wavelengths, 633 nm and 905 nm. The results show that: (1) The particle size distributions can be differentiated by measuring the phase ratio A(α1)/A(α2), and in order to increase the discriminative power of the particle size distribution, the value of (α1-α2) should be as large as possible. (2) For pure minerals, larger grains have smaller phase ratio values, because larger grains of pure minerals are more forward scattering, leading to larger A(α2) and thus smaller phase ratio. For mixtures with simulated agglutinates that hold minerals together as composite particles, larger grains have higher phase ratios because they are less forward scattering due to multiple internal reflections and hence more absorptions. Since real planetary regoliths are likely dominated by composite particles with agglutinates, it is expected that larger grains would have larger phase ratio values.