ABSTRACT
The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater's sedimentary delta, finding that the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Magnesium-iron carbonates along grain boundaries indicate reactions with carbon dioxide-rich water under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks have been stored aboard Perseverance for potential return to Earth.
ABSTRACT
The geological units on the floor of Jezero crater, Mars, are part of a wider regional stratigraphy of olivine-rich rocks, which extends well beyond the crater. We investigated the petrology of olivine and carbonate-bearing rocks of the Séítah formation in the floor of Jezero. Using multispectral images and x-ray fluorescence data, acquired by the Perseverance rover, we performed a petrographic analysis of the Bastide and Brac outcrops within this unit. We found that these outcrops are composed of igneous rock, moderately altered by aqueous fluid. The igneous rocks are mainly made of coarse-grained olivine, similar to some martian meteorites. We interpret them as an olivine cumulate, formed by settling and enrichment of olivine through multistage cooling of a thick magma body.
ABSTRACT
The ROMA database (ROck reflectance for MArtian in situ exploration, https://roma.univ-lyon1.fr) provides the reflectance spectra between 0.4 and 3-4 µm of various terrestrial, Martian, and synthetic samples, as a means to document reference measurements for comparison with data acquired by visible and near-infrared spectrometers on planetary surfaces, with a focus on current and future Martian observations by the Perseverance (Mars 2020 mission) and Rosalind Franklin (ExoMars) rovers. The main specificity of this database is to include a significant fraction of spectra of unprocessed rock, which are more realistic analogs and often have different spectral features than the fine powders more commonly analyzed in reflectance spectroscopy. Additionally, these measurements were acquired with a spectrometer whose spot size is similar to those of the SuperCam instrument (Mars 2020 mission) at a few meters from a target. Supplementary information are provided in the ROMA database: higher-level data (such as absorption band parameters) as well as sample mineralogy estimated by whole-rock X-ray diffraction analyses. Future comparisons with this database will help improve the interpretation of spectral measurements acquired on the Martian surface. This work introduces the aim of the library and its current state, but additional data on intact natural rock surfaces will likely be added in the future.
ABSTRACT
OBJECTIVES: To observe whether medical complications, the evolution of neurological disorders and dependence and/or the discharge destinations are different for patients treated by craniectomy for malignant cerebral infarction in the middle cerebral artery compared to patients treated medically for severe or malignant cerebral infarction in the same cerebral territory, during their hospitalization in a physical medicine and rehabilitation department. PATIENTS AND METHODS: This retrospective study compared patients treated by craniectomy for malignant cerebral infarction in the middle cerebral artery and patients treated medically for severe or malignant cerebral infarction in the same cerebral territory. Patients were paired according to age, lesion side and hospitalization period. RESULTS: Twelve patients treated by craniectomy (age 43+/-10.44) were paired with 12 patients treated medically (age 49+/-7.66). The two groups were comparable in terms of general undesirable medical events. The medical events related to craniectomy are described. The evolution of patient deficiencies, the length of the hospital stay (194+/-118.93 days vs 152+/-94.64 days), the Functional Independence Measure at discharge (87+/-21.28 vs 95+/-22.19) and the number of direct home discharges (7 vs 9) did not significantly differ between groups. DISCUSSION AND CONCLUSION: No more medical problems were observed in the patients treated by craniectomy than in the patients treated medically, except for the medical events specifically related to craniectomy, which extended the hospital stay but had no major repercussions.
