Christophe Donny

Samples from the Rocknest aeolian deposit were heated to ~835°C under helium flow and evolved gases analyzed by Curiosity's Sample Analysis at Mars instrument suite. H2O, SO2, CO2, and O2 were the major gases released. Water abundance (1.5 to 3 weight percent) and release temperature suggest that H2O is bound within an amorphous component of the sample. Decomposition of fine-grained Fe or Mg carbonate is the likely source of much of the evolved CO2. Evolved O2 is coincident with the release of Cl, suggesting that oxygen is produced from thermal decomposition of an oxychloride compound. Elevated δD values are consistent with recent atmospheric exchange. Carbon isotopes indicate multiple carbon sources in the fines. Several simple organic compounds were detected, but they are not definitively martian in origin.

Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine-rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.

"Jake_M," the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the Curiosity rover, differs substantially in chemical composition from other known martian igneous rocks: It is alkaline (>15% normative nepheline) and relatively fractionated. Jake_M is compositionally similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. By analogy with these comparable terrestrial rocks, Jake_M could have been produced by extensive fractional crystallization of a primary alkaline or transitional magma at elevated pressure, with or without elevated water contents. The discovery of Jake_M suggests that alkaline magmas may be more abundant on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).

The MMX InfraRed Spectrometer (MIRS) is a spectro-imager on board the Japan Aerospace Exploration Agency Martian Moons eXploration mission, set to launch in 2026, to investigate the origin of the Martian moons, Phobos and Deimos, as well as the Martian atmosphere and surface. MIRS, operating in the 0.9-3.6 μm wavelength range, is designed to identify and map minerals, ices, and organic compounds on the Martian moons, while also monitoring water vapor and dust in Mars's atmosphere. This paper details the ground calibration and performance evaluation of the MIRS Flight Model, conducted at the Laboratory for Instrumentation and Research in Astrophysics at the Paris Observatory during the thermal-vacuum test campaign at the end of 2023. A detailed description of the apparatus and the procedures used during the campaign is provided. The calibration campaign tested the instrument's thermal response and radiometric performance, ensuring compliance with stringent mission requirements. The tests demonstrated MIRS's capability to deliver high-resolution spectral data, fulfilling critical scientific and technical objectives. The preliminary results indicate MIRS's readiness for in-flight operations and its potential to contribute significantly to the understanding of the Mars system.