Calibration of MAJIS (Moons And Jupiter Imaging Spectrometer). II. Spatial calibration.

MAJIS, Moons and Jupiter Imaging Spectrometer, is one of the scientific payloads aboard European Space Agency's Jupiter Icy Moons Explorer mission. This instrument underwent a comprehensive characterization and calibration campaign before integration on the spacecraft. In this work, we report on the measurements of the instrumental spatial responses, including the slit and pixel functions, the knife edge function, the ensquared energy, and the keystone aberration. The measurements were repeated in several positions of the field of view and within the range of MAJIS temperatures during science observations. The goal was to characterize the instrument's response under a wide set of conditions and at different visible-infrared wavelengths. The experimental setups employed to perform calibrations are described in detail, and the methodology applied to derive the instrumental spatial responses is discussed. After launch, minor changes in the instrument response and the coalignment between the two spectral channels were identified by comparing on-ground data with the first in-flight data returned by MAJIS.

Calibration of MAJIS (Moons And Jupiter Imaging Spectrometer). III. Spectral calibration.

The Moons And Jupiter Imaging Spectrometer (MAJIS) is the visible and near-infrared imaging spectrometer onboard the European Space Agency (ESA)'s Jupiter Icy Moons Explorer mission. Before its integration into the spacecraft, the instrument undergoes an extensive ground calibration to establish its baseline performances. This process prepares the imaging spectrometer for flight operations by characterizing the behavior of the instrument under various operative conditions and uncovering instrumental distortions that may depend on instrumental commands. Two steps of the on-ground calibration campaigns were held at the instrument level to produce the data. Additional in-flight measurements have recently been obtained after launch during the Near-Earth Commissioning Phase. In this article, we present the analyses of these datasets, focusing on the characterization of the spectral performances. First, we describe and analyze the spectral calibration datasets obtained using both monochromatic sources and polychromatic sources coupled with solid and gas samples. Then, we derive the spectral sampling and the spectral response function over the entire field of view. These spectral characteristics are quantified for various operational parameters of MAJIS, such as temperature and spectral binning. The derived on-ground performances are then compared with in-flight measurements obtained after launch and presented in the framework of the MAJIS performance requirements.

Jupiter Science Enabled by ESA's Jupiter Icy Moons Explorer.

ESA's Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and space-based observatories. We focus on remote sensing of the climate, meteorology, and chemistry of the atmosphere and auroras from the cloud-forming weather layer, through the upper troposphere, into the stratosphere and ionosphere. The Jupiter orbital tour provides a wealth of opportunities for atmospheric and auroral science: global perspectives with its near-equatorial and inclined phases, sampling all phase angles from dayside to nightside, and investigating phenomena evolving on timescales from minutes to months. The remote sensing payload spans far-UV spectroscopy (50-210 nm), visible imaging (340-1080 nm), visible/near-infrared spectroscopy (0.49-5.56 µm), and sub-millimetre sounding (near 530-625 GHz and 1067-1275 GHz). This is coupled to radio, stellar, and solar occultation opportunities to explore the atmosphere at high vertical resolution; and radio and plasma wave measurements of electric discharges in the Jovian atmosphere and auroras. Cross-disciplinary scientific investigations enable JUICE to explore coupling processes in giant planet atmospheres, to show how the atmosphere is connected to (i) the deep circulation and composition of the hydrogen-dominated interior; and (ii) to the currents and charged particle environments of the external magnetosphere. JUICE will provide a comprehensive characterisation of the atmosphere and auroras of this archetypal giant planet.

Compositionally and density stratified igneous terrain in Jezero crater, Mars.

Before Perseverance, Jezero crater's floor was variably hypothesized to have a lacustrine, lava, volcanic airfall, or aeolian origin. SuperCam observations in the first 286 Mars days on Mars revealed a volcanic and intrusive terrain with compositional and density stratification. The dominant lithology along the traverse is basaltic, with plagioclase enrichment in stratigraphically higher locations. Stratigraphically lower, layered rocks are richer in normative pyroxene. The lowest observed unit has the highest inferred density and is olivine-rich with coarse (1.5 millimeters) euhedral, relatively unweathered grains, suggesting a cumulate origin. This is the first martian cumulate and shows similarities to martian meteorites, which also express olivine disequilibrium. Alteration materials including carbonates, sulfates, perchlorates, hydrated silicates, and iron oxides are pervasive but low in abundance, suggesting relatively brief lacustrine conditions. Orbital observations link the Jezero floor lithology to the broader Nili-Syrtis region, suggesting that density-driven compositional stratification is a regional characteristic.

Planetary Terrestrial Analogues Library Project: 3. Characterization of Samples With MicrOmega.

The Planetary Terrestrial Analogues Library (PTAL) project aims at building and exploiting a database involving several analytical techniques, to help characterize the mineralogical evolution of terrestrial bodies, starting with Mars. Around 100 natural Earth rock samples have been collected from selected locations to gather a variety of analogs for martian geology, from volcanic to sedimentary origin with different levels of alteration. All samples are to be characterized within the PTAL project with different mineralogical and elemental analysis techniques, including techniques brought on actual and future instruments at the surface of Mars (near infrared [NIR] spectroscopy, Raman spectroscopy, and laser-induced breakdown spectroscopy). This article presents the NIR measurements and interpretations acquired with the ExoMars MicrOmega spare instrument. MicrOmega is an NIR hyperspectral microscope, mounted in the analytical laboratory of the ExoMars rover Rosalind Franklin. All PTAL samples have been observed at least once with MicrOmega using a dedicated setup. For all PTAL samples, data description and interpretation are presented. For some chosen examples, color composite images and spectra are presented as well. A comparison with characterizations by NIR and Raman spectrometry is discussed for some of the samples. In particular, the spectral imaging capacity of MicrOmega allows detections of mineral components and potential organic molecules that were not possible with other one-spot techniques. In addition, it enables estimation of heterogeneities in the spatial distribution of various mineral species. The MicrOmega/PTAL data shall support the future observations and analyses performed by MicrOmega/Rosalind Franklin instrument.

Mineralogical and Spectral (Near-Infrared) Characterization of Fe-Rich Vermiculite-Bearing Terrestrial Deposits and Constraints for Mineralogy of Oxia Planum, ExoMars 2022 Landing Site.

Oxia Planum is a Noachian plain on Mars. It was chosen as the final landing site for in situ studies by ExoMars 2022 rover. The main scientific objectives of the mission are to understand the mineralogy and aqueous evolution of ancient Mars with relevance to habitability. Oxia is covered by vast deposits of Fe,Mg-phyllosilicates, but the exact nature of these deposits is not yet fully understood. We performed a survey of potential terrestrial analog rocks, and here we show combined mineralogical characterization of these rocks with their near-infrared spectral analysis. Samples from two terrestrial sites were studied: (1) vermiculitized chlorite-schists from Otago, New Zealand, which underwent an alteration process without significant oxidation; and (2) basaltic tuffs from Granby, Massachusetts, USA, with Fe-rich clays filling amygdales of supposedly hydrothermal origin. Both analogues are incorporated into the newly built Planetary Terrestrial Analogue Library (PTAL) collection. Oxia bedrock clay-rich deposits are spectrally matched best by a well-crystallized trioctahedral vermiculite/saponite mixture from the basaltic tuff, although the contribution of saponite must be minor. Otago vermiculite is a good analogue to Oxia vermiculite in terms of overall mineralogy and Fe content. However, spectral inconsistencies related to the Al content in the Otago clays indicate that illitization of vermiculite, which results from postalteration oxidation, did not occur at Oxia. This implies limited water/rock interactions and reducing conditions during deposition of sediments now constituting the bedrock at Oxia. Whereas the spectral match does not conclusively imply the mineralogy, trioctahedral vermiculite should be considered a likely mineral component of the bedrock unit at Oxia Planum. Vermiculite has great potential to store organic matter, and the postdeposition geological context of Oxia Planum derived from understanding of environmental conditions in analog sites is promising for organic matter preservation.

ExoMars Raman Laser Spectrometer: A Tool to Semiquantify the Serpentinization Degree of Olivine-Rich Rocks on Mars.

We evaluated the effectiveness of the ExoMars Raman laser spectrometer (RLS) to determine the degree of serpentinization of olivine-rich units on Mars. We selected terrestrial analogs of martian ultramafic rocks from the Leka Ophiolite Complex (LOC) and analyzed them with both laboratory and flight-like analytical instruments. We first studied the mineralogical composition of the samples (mostly olivine and serpentine) with state-of-the-art diffractometric (X-ray diffractometry [XRD]) and spectroscopic (Raman, near-infrared spectroscopy [NIR]) laboratory systems. We compared these results with those obtained using our RLS ExoMars Simulator. Our work shows that the RLS ExoMars Simulator successfully identified all major phases. Moreover, when emulating the automatic operating mode of the flight instrument, the RLS ExoMars Simulator also detected several minor compounds (pyroxene and brucite), some of which were not observed by NIR and XRD (e.g., calcite). Thereafter, we produced RLS-dedicated calibration curves (R2 between 0.9993 and 0.9995 with an uncertainty between ±3.0% and ±5.2% with a confidence interval of 95%) to estimate the relative content of olivine and serpentine in the samples. Our results show that RLS can be very effective in identifying serpentine, a scientific target of primary importance for the potential detection of biosignatures on Mars-the main objective of the ExoMars rover mission.

Mawrth Vallis, Mars: A Fascinating Place for Future In Situ Exploration.

After the successful landing of the Mars Science Laboratory rover, both NASA and ESA initiated a selection process for potential landing sites for the Mars2020 and ExoMars missions, respectively. Two ellipses located in the Mawrth Vallis region were proposed and evaluated during a series of meetings (three for Mars2020 mission and five for ExoMars). We describe here the regional context of the two proposed ellipses as well as the framework of the objectives of these two missions. Key science targets of the ellipses and their astrobiological interests are reported. This work confirms that the proposed ellipses contain multiple past martian wet environments of a subaerial, subsurface, and/or subaqueous character, in which to probe the past climate of Mars; build a broad picture of possible past habitable environments; evaluate their exobiological potentials; and search for biosignatures in well-preserved rocks. A mission scenario covering several key investigations during the nominal mission of each rover is also presented, as well as descriptions of how the site fulfills the science requirements and expectations of in situ martian exploration. These serve as a basis for potential future exploration of the Mawrth Vallis region with new missions and describe opportunities for human exploration of Mars in terms of resources and science discoveries.

ExoMars Raman Laser Spectrometer: A Tool for the Potential Recognition of Wet-Target Craters on Mars.

In the present work, near-infrared, laser-induced breakdown spectroscopy, Raman, and X-ray diffractometer techniques have been complementarily used to carry out a comprehensive characterization of a terrestrial analogue selected from the Chesapeake Bay impact structure (CBIS). The obtained data clearly highlight the key role of Raman spectroscopy in the detection of minor and trace compounds, through which inferences about geological processes occurred in the CBIS can be extrapolated. Beside the use of commercial systems, further Raman analyses were performed by the Raman laser spectrometer (RLS) ExoMars Simulator. This instrument represents the most reliable tool to effectively predict the scientific capabilities of the ExoMars/Raman system that will be deployed on Mars in 2021. By emulating the analytical procedures and operational restrictions established by the ExoMars mission rover design, it was proved that the RLS ExoMars Simulator can detect the amorphization of quartz, which constitutes an analytical clue of the impact origin of craters. Beside amorphized minerals, the detection of barite and siderite, compounds crystallizing under hydrothermal conditions, helps indirectly to confirm the presence of water in impact targets. Furthermore, the RLS ExoMars Simulator capability of performing smart molecular mappings was successfully evaluated.

Spectroscopic study of olivine-bearing rocks and its relevance to the ExoMars rover mission.

We present the compositional analysis of three terrestrial analogues of Martian olivine-bearing rocks derived from both laboratory and flight-derived analytical instruments. In the first step, state-of-the-art spectroscopic (XRF, NIR and Raman) and diffractometric (XRD) laboratory systems were complementary used. Besides providing a detailed mineralogical and geochemical characterization of the samples, results comparison shed light on the advantages ensured by the combined use of Raman and NIR techniques, being these the spectroscopic instruments that will soon deploy (2021) on Mars as part of the ExoMars/ESA rover payload. In order to extrapolate valuable indicators of the mineralogical data that could derive from the ExoMars/Raman Laser Spectrometer (RLS), laboratory results were then compared with the molecular data gathered through the RLS ExoMars Simulator. Beside correctly identifying all major phases (feldspar, pyroxene and olivine), the RLS ExoMars Simulator confirmed the presence of additional minor compounds (i.e. hematite and apatite) that were not detected by complementary techniques. Furthermore, concerning the in-depth study of olivine grains, the RLS ExoMars simulator was able to effectively detect the shifting of the characteristic double peak around 820 and 850 cm-1, from which the FeMg content of the analyzed crystals can be extrapolated. Considering that olivine is one of the main mineral phases of the ExoMars landing site (Oxia Planum), this study suggests that the ExoMars/RLS system has the potential to provide detailed information about the elemental composition of olivine on Mars.

Infrared Spectrometer for ExoMars: A Mast-Mounted Instrument for the Rover.

ISEM (Infrared Spectrometer for ExoMars) is a pencil-beam infrared spectrometer that will measure reflected solar radiation in the near infrared range for context assessment of the surface mineralogy in the vicinity of the ExoMars rover. The instrument will be accommodated on the mast of the rover and will be operated together with the panoramic camera (PanCam), high-resolution camera (HRC). ISEM will study the mineralogical and petrographic composition of the martian surface in the vicinity of the rover, and in combination with the other remote sensing instruments, it will aid in the selection of potential targets for close-up investigations and drilling sites. Of particular scientific interest are water-bearing minerals, such as phyllosilicates, sulfates, carbonates, and minerals indicative of astrobiological potential, such as borates, nitrates, and ammonium-bearing minerals. The instrument has an ∼1° field of view and covers the spectral range between 1.15 and 3.30 µm with a spectral resolution varying from 3.3 nm at 1.15 µm to 28 nm at 3.30 µm. The ISEM optical head is mounted on the mast, and its electronics box is located inside the rover's body. The spectrometer uses an acousto-optic tunable filter and a Peltier-cooled InAs detector. The mass of ISEM is 1.74 kg, including the electronics and harness. The science objectives of the experiment, the instrument design, and operational scenarios are described. Key Words: ExoMars-ISEM-Mars-Surface-Mineralogy-Spectroscopy-AOTF-Infrared. Astrobiology 17, 542-564.

The source crater of martian shergottite meteorites.

Absolute ages for planetary surfaces are often inferred by crater densities and only indirectly constrained by the ages of meteorites. We show that the <5 million-year-old and 55-km-wide Mojave Crater on Mars is the ejection source for the meteorites classified as shergottites. Shergottites and this crater are linked by their coinciding meteorite ejection ages and the crater formation age and by mineralogical constraints. Because Mojave formed on 4.3 billion-year-old terrain, the original crystallization ages of shergottites are old, as inferred by Pb-Pb isotope ratios, and the much-quoted shergottite ages of <600 million years are due to resetting. Thus, the cratering-based age determination method for Mars is now calibrated in situ, and it shifts the absolute age of the oldest terrains on Mars backward by 200 million years.

The Mawrth Vallis region of Mars: A potential landing site for the Mars Science Laboratory (MSL) mission.

The primary objective of NASA's Mars Science Laboratory (MSL) mission, which will launch in 2011, is to characterize the habitability of a site on Mars through detailed analyses of the composition and geological context of surface materials. Within the framework of established mission goals, we have evaluated the value of a possible landing site in the Mawrth Vallis region of Mars that is targeted directly on some of the most geologically and astrobiologically enticing materials in the Solar System. The area around Mawrth Vallis contains a vast (>1 × 106 km²) deposit of phyllosilicate-rich, ancient, layered rocks. A thick (>150 m) stratigraphic section that exhibits spectral evidence for nontronite, montmorillonite, amorphous silica, kaolinite, saponite, other smectite clay minerals, ferrous mica, and sulfate minerals indicates a rich geological history that may have included multiple aqueous environments. Because phyllosilicates are strong indicators of ancient aqueous activity, and the preservation potential of biosignatures within sedimentary clay deposits is high, martian phyllosilicate deposits are desirable astrobiological targets. The proposed MSL landing site at Mawrth Vallis is located directly on the largest and most phyllosilicate-rich deposit on Mars and is therefore an excellent place to explore for evidence of life or habitability.

Key scientific questions and key investigations from the first international conference on Martian phyllosilicates.

Minerals and their occurrences can tell us about the chemistry, pressure, and temperatures of past environments on Mars and thus allow inferences about the potential for habitability. Thanks to recent space exploration, a new vision is emerging wherein Mars hosted environmental conditions of potential astrobiological relevance. This epoch is identified by the presence of phyllosilicate-bearing deposits, which are generally contained in very ancient basement rocks. In October 2008, over 100 planetary scientists representing 11 countries met in Paris to assess and discuss the relevance of martian phyllosilicates. The conference was structured to promote the discussion and debate of key scientific questions and key essential investigations. The purpose of this report is to document the current state of knowledge related to martian phyllosilicates and to ascertain which questions remain to be addressed: What are the basic characteristics of the phyllosilicate minerals on Mars? What are the genetic mechanisms by which phyllosilicate minerals have formed on Mars? What is the relationship between the phyllosilicate minerals observed in martian meteorites and those detected from orbit? What are the implications of phyllosilicate-bearing rocks for the development of prebiotic chemistry and the preservation of biosignatures? The most promising investigations to address these questions are presented.

Orbital identification of carbonate-bearing rocks on Mars.

Geochemical models for Mars predict carbonate formation during aqueous alteration. Carbonate-bearing rocks had not previously been detected on Mars' surface, but Mars Reconnaissance Orbiter mapping reveals a regional rock layer with near-infrared spectral characteristics that are consistent with the presence of magnesium carbonate in the Nili Fossae region. The carbonate is closely associated with both phyllosilicate-bearing and olivine-rich rock units and probably formed during the Noachian or early Hesperian era from the alteration of olivine by either hydrothermal fluids or near-surface water. The presence of carbonate as well as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering, proposed to be characteristic of Hesperian Mars, did not destroy these carbonates and thus did not dominate all aqueous environments.

Phyllosilicate diversity and past aqueous activity revealed at Mawrth Vallis, Mars.

Observations by the Mars Reconnaissance Orbiter/Compact Reconnaissance Imaging Spectrometer for Mars in the Mawrth Vallis region show several phyllosilicate species, indicating a wide range of past aqueous activity. Iron/magnesium (Fe/Mg)-smectite is observed in light-toned outcrops that probably formed via aqueous alteration of basalt of the ancient cratered terrain. This unit is overlain by rocks rich in hydrated silica, montmorillonite, and kaolinite that may have formed via subsequent leaching of Fe and Mg through extended aqueous events or a change in aqueous chemistry. A spectral feature attributed to an Fe2+ phase is present in many locations in the Mawrth Vallis region at the transition from Fe/Mg-smectite to aluminum/silicon (Al/Si)-rich units. Fe2+-bearing materials in terrestrial sediments are typically associated with microorganisms or changes in pH or cations and could be explained here by hydrothermal activity. The stratigraphy of Fe/Mg-smectite overlain by a ferrous phase, hydrated silica, and then Al-phyllosilicates implies a complex aqueous history.

Early geochemical environment of Mars as determined from thermodynamics of phyllosilicates.

Images of geomorphological features that seem to have been produced by the action of liquid water have been considered evidence for wet surface conditions on early Mars. Moreover, the recent identification of large deposits of phyllosilicates, associated with the ancient Noachian terrains suggests long-timescale weathering of the primary basaltic crust by liquid water. It has been proposed that a greenhouse effect resulting from a carbon-dioxide-rich atmosphere sustained the temperate climate required to maintain liquid water on the martian surface during the Noachian. The apparent absence of carbonates and the low escape rates of carbon dioxide, however, are indicative of an early martian atmosphere with low levels of carbon dioxide. Here we investigate the geochemical conditions prevailing on the surface of Mars during the Noachian period using calculations of the aqueous equilibria of phyllosilicates. Our results show that Fe3+-rich phyllosilicates probably precipitated under weakly acidic to alkaline pH, an environment different from that of the following period, which was dominated by strongly acid weathering that led to the sulphate deposits identified on Mars. Thermodynamic calculations demonstrate that the oxidation state of the martian surface was already high, supporting early escape of hydrogen. Finally, equilibrium with carbonates implies that phyllosilicate precipitation occurs preferentially at a very low partial pressure of carbon dioxide. We suggest that the possible absence of Noachian carbonates more probably resulted from low levels of atmospheric carbon dioxide, rather than primary acidic conditions. Other greenhouse gases may therefore have played a part in sustaining a warm and wet climate on the early Mars.

Diffuse reflectance infrared Fourier transform spectroscopy as a tool to characterise water in adsorption/confinement situations.

We present experimental data acquired by diffuse reflectance infrared spectroscopy in the mid-IR (4000-400 cm(-1)), on micrometric-sized mineral grain powders. The spectral evolution of the OH-stretching band is followed when the adsorbed water film is thinned under dry conditions, from high to low hydration states. The IR bands are found to be characteristic of the degree of adsorption/confinement of the liquid water. The OH-stretching band is shifted toward shorter wavenumbers than in bulk water, showing that a significant portion of adsorbed water has a higher intermolecular bonding energy. Complementary treatment of the kinetics of water desorption, varying with the surface forces in the water film, confirms the relationships of these bands with the constrained water state. We distinguish different water types obeying liquid-liquid interactions (free and capillary water) or dominated by solid-water interactions (confined and adsorbed water). Part of this study is devoted to mesoporous silica MCM-41, of interest due to the restricted geometries of its mesopores (4.7 nm) favouring the confined water state. The methodology allows us to distinguish bulk and adsorbed/confined water, using spectral analysis coupled with an understanding of the dynamic behaviour of the desorption process.

No signature of clear CO2 ice from the 'cryptic' regions in Mars' south seasonal polar cap.

The seasonal polar ice caps of Mars are composed mainly of CO2 ice. A region of low (< 30%) albedo has been observed within the south seasonal cap during early to mid-spring. The low temperature of this 'cryptic region' has been attributed to a clear slab of nearly pure CO2 ice, with the low albedo resulting from absorption by the underlying surface. Here we report near-infrared imaging spectroscopy of the south seasonal cap. The deep and broad CO2 absorption bands that are expected in the near-infrared with a thick transparent slab of CO2 ice are not observed. Models of the observed spectra indicate that the low albedo results from extensive dust contamination close to the surface of a CO2 ice layer, which could be linked to atmospheric circulation patterns. The strength of the CO2 absorption increases after mid-spring, so part of the dust is either carried away or buried more deeply in the ice layer during the CO2 ice sublimation process.

Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data.

Global mineralogical mapping of Mars by the Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activité (OMEGA) instrument on the European Space Agency's Mars Express spacecraft provides new information on Mars' geological and climatic history. Phyllosilicates formed by aqueous alteration very early in the planet's history (the "phyllocian" era) are found in the oldest terrains; sulfates were formed in a second era (the "theiikian" era) in an acidic environment. Beginning about 3.5 billion years ago, the last era (the "siderikian") is dominated by the formation of anhydrous ferric oxides in a slow superficial weathering, without liquid water playing a major role across the planet.