Alkali magmatism on Mars: an unexpected diversity

Despite an apparent north/south topographic dichotomy that formed ${>}$4.0 Ga, the young Martian meteorites (${<}$2.4 Ga) and first-order remote sensing observations revealed a surface of Mars that is uniformly basaltic. This simplistic vision has been challenged by the discovery of a brecciated meteorite and additional spacecraft data that all point to the presence of alkaline igneous rocks, thereby demonstrating an unexpected igneous diversity on Mars. In the present paper, we review a variety of effusive alkaline rocks (basalts to trachytes) recognized so far in the southern hemisphere of Mars as observed from a unique 4.47 Ga Martian meteorite, as well as ground, and orbital data. The complementary of effusive alkaline rocks and plutonic orthopyroxene-rich rocks in early Mars is discussed. We propose that mantle-derived magmas at high extent of melting at rather low pressure either erupted forming orthopyroxene-rich lavas, or crystallized at shallow crustal depths, fractionating orthopyroxene which sank to the bottom of the chamber and residual alkaline magmas which erupted at the surface of Mars. Widespread low pressure fractionation processes could also be related to heavy bombardment on the early Martian crust generating melt sheets that ultimately differentiated. The Noachian crust is more diverse than being merely basaltic

Alkali magmatism on Mars: an unexpected diversity

Despite an apparent north/south topographic dichotomy that formed ${>}$4.0 Ga, the young Martian meteorites (${<}$2.4 Ga) and first-order remote sensing observations revealed a surface of Mars that is uniformly basaltic. This simplistic vision has been challenged by the discovery of a brecciated meteorite and additional spacecraft data that all point to the presence of alkaline igneous rocks, thereby demonstrating an unexpected igneous diversity on Mars. In the present paper, we review a variety of effusive alkaline rocks (basalts to trachytes) recognized so far in the southern hemisphere of Mars as observed from a unique 4.47 Ga Martian meteorite, as well as ground, and orbital data. The complementary of effusive alkaline rocks and plutonic orthopyroxene-rich rocks in early Mars is discussed. We propose that mantle-derived magmas at high extent of melting at rather low pressure either erupted forming orthopyroxene-rich lavas, or crystallized at shallow crustal depths, fractionating orthopyroxene which sank to the bottom of the chamber and residual alkaline magmas which erupted at the surface of Mars. Widespread low pressure fractionation processes could also be related to heavy bombardment on the early Martian crust generating melt sheets that ultimately differentiated. The Noachian crust is more diverse than being merely basaltic

Trace element geochemistry (Li, Ba, Sr, and Rb) using Curiosity's ChemCam: Early results for Gale crater from Bradbury Landing Site to Rocknest

The ChemCam instrument package on the Mars rover, Curiosity, provides new capabilities to probe the abundances of certain trace elements in the rocks and soils on Mars using the laser-induced breakdown spectroscopy technique. We focus on detecting and quantifying Li, Ba, Rb, and Sr in targets analyzed during the first 100 sols, from Bradbury Landing Site to Rocknest. Univariate peak area models and multivariate partial least squares models are presented. Li, detected for the first time directly on Mars, is generally low (100 ppm and >1000 ppm, respectively. These analysis locations tend to have high Si and alkali abundances, consistent with a feldspar composition. Together, these trace element observations provide possible evidence of magma differentiation and aqueous alteration. Key Points Quantitative models for Li, Ba, Rb and Sr using ChemCam data are presented Abundances for the first 100 sols in Gale crater are discussed These results represent the first in situ measurements of Li and Ba on Mar

Centimeter to decimeter hollow concretions and voids in Gale Crater sediments, Mars

Voids and hollow spheroids between ∼1 and 23 cm in diameter occur at several locations along the traverse of the Curiosity rover in Gale crater, Mars. These hollow spherical features are significantly different from anything observed in previous landed missions. The voids appear in dark-toned, rough-textured outcrops, most notably at Point Lake (sols 302-305) and Twin Cairns Island (sol 343). Point Lake displays both voids and cemented spheroids in close proximity; other locations show one or the other form. The spheroids have 1-4 mm thick walls and appear relatively dark-toned in all cases, some with a reddish hue. Only one hollow spheroid (Winnipesaukee, sol 653) was analyzed for composition, appearing mafic (Fe-rich), in contrast to the relatively felsic host rock. The interior surface of the spheroid appears to have a similar composition to the exterior with the possible exceptions of being more hydrated and slightly depleted in Fe and K. Origins of the spheroids as Martian tektites or volcanic bombs appear unlikely due to their hollow and relatively fragile nature and the absence of in-place clearly igneous rocks. A more likely explanation to both the voids and the hollow spheroids is reaction of reduced iron with oxidizing groundwater followed by some re-precipitation as cemented rind concretions at a chemical reaction front. Although some terrestrial concretion analogs are produced from a precursor siderite or pyrite, diagenetic minerals could also be direct precipitates for other terrestrial concretions. The Gale sediments differ from terrestrial sandstones in their high initial iron content, perhaps facilitating a higher occurrence of such diagenetic reactions

The SuperCam Instrument Suite on the Mars 2020 Rover: Science Objectives and Mast-Unit Description

On the NASA 2020 rover mission to Jezero crater, the remote determination of the texture, mineralogy and chemistry of rocks is essential to quickly and thoroughly characterize an area and to optimize the selection of samples for return to Earth. As part of the Perseverance payload, SuperCam is a suite of five techniques that provide critical and complementary observations via Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), visible and near-infrared spectroscopy (VISIR), high-resolution color imaging (RMI), and acoustic recording (MIC). SuperCam operates at remote distances, primarily 2-7 m, while providing data at sub-mm to mm scales. We report on SuperCam's science objectives in the context of the Mars 2020 mission goals and ways the different techniques can address these questions. The instrument is made up of three separate subsystems: the Mast Unit is designed and built in France; the Body Unit is provided by the United States; the calibration target holder is contributed by Spain, and the targets themselves by the entire science team. This publication focuses on the design, development, and tests of the Mast Unit; companion papers describe the other units. The goal of this work is to provide an understanding of the technical choices made, the constraints that were imposed, and ultimately the validated performance of the flight model as it leaves Earth, and it will serve as the foundation for Mars operations and future processing of the data.In France was provided by the Centre National d'Etudes Spatiales (CNES). Human resources were provided in part by the Centre National de la Recherche Scientifique (CNRS) and universities. Funding was provided in the US by NASA's Mars Exploration Program. Some funding of data analyses at Los Alamos National Laboratory (LANL) was provided by laboratory-directed research and development funds

SuperCam Calibration Targets: Design and Development

SuperCam is a highly integrated remote-sensing instrumental suite for NASA’s Mars 2020 mission. It consists of a co-aligned combination of Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), Visible and Infrared Spectroscopy (VISIR), together with sound recording (MIC) and high-magnification imaging techniques (RMI). They provide information on the mineralogy, geochemistry and mineral context around the Perseverance Rover. The calibration of this complex suite is a major challenge. Not only does each technique require its own standards or references, their combination also introduces new requirements to obtain optimal scientific output. Elemental composition, molecular vibrational features, fluorescence, morphology and texture provide a full picture of the sample with spectral information that needs to be co-aligned, correlated, and individually calibrated. The resulting hardware includes different kinds of targets, each one covering different needs of the instrument. Standards for imaging calibration, geological samples for mineral identification and chemometric calculations or spectral references to calibrate and evaluate the health of the instrument, are all included in the SuperCam Calibration Target (SCCT). The system also includes a specifically designed assembly in which the samples are mounted. This hardware allows the targets to survive the harsh environmental conditions of the launch, cruise, landing and operation on Mars during the whole mission. Here we summarize the design, development, integration, verification and functional testing of the SCCT. This work includes some key results obtained to verify the scientific outcome of the SuperCam system

Igneous composition vaiations determined by ChemCam along Curiosity’s traverse from Bradbury to Rocknest area at Gale crater, Mars

Upprättat; 2013; 20150701 (ninhul

Marble quarries in Delos Island (Greece): a geological characterization

International audienceTraces of extraction in Delian marble quarries attest their exploitation during Antiquity. A preliminary non-destructive provenance study confirmed the presence of indigenous marble in Delos constructions. In contrast, Delos marble quarries have not been geochemically described so far. Therefore, a detailed (1/5000 scale) geological mapping and cross-sections were performed in the four Delian marble quarries in order to better determine their dimension and to estimate the volume of extracted marble. The surface of the quarries was revised into up to six times larger areas, increasing the extracted volume estimations. Quarries were sampled and studied with mineralo-petrographic (optical and electronic microscopy, X-Ray Diffraction) and isotopic (δ 13 C and δ 18 O) characterization. Three categories were observed, i.e. , a coarse whitish to bluish marble, a fine yellowish dolomitic marble and marble with giant white and blue calcite crystals. The Maximum Grain Size associated with oxygen and carbon isotopic ratios showed a good potential to distinguish Delian marbles from most of the main Mediterranean marbles used during Antiquity. However, geochemical elemental analyses such as trace elements analysis could supplement Delian marble characterization which will benefit future provenance studies.Des traces d’extraction dans les carrières de marbre de Délos attestent de leur exploitation durant l’Antiquité. Une première étude géochimique non destructive a permis d’identifier du marbre dans les constructions de Délos. Toutefois les carrières n’avaient jamais fait l’objet d’une étude géochimique détaillée jusque-là. Par conséquent, une carte géologique détaillée (échelle 1/5000) ainsi que des coupes géologiques ont été réalisées dans les quatre carrières de marbre afin de mieux cerner la dimension des carrières et les volumes de marbre qui en ont été extraits. La surface des carrières a été largement revue à la hausse, atteignant jusqu’à six fois la surface de la précédente cartographie des carrières, ce qui augmente donc considérablement le volume théorique de marbre extrait à Délos. Les carrières ont été échantillonnées et étudiées par une caractérisation minéralo-pétrographique (microscopie optique et électronique, diffraction de rayons X) et isotopique (δ 13 C et δ 18 O). Trois catégories ont été observées, à savoir un marbre grossier blanchâtre à bleuté, un marbre dolomitique jaunâtre fin et un marbre à cristaux géants de calcite blanche et bleue. La taille maximale des grains associée aux rapports isotopiques de l’oxygène et du carbone ont montré un bon potentiel pour distinguer les marbres déliens de la plupart des principaux marbres Méditerranéens utilisés durant l’Antiquité. Cependant, des analyses géochimiques élémentaires comme l’analyse des éléments traces dans la calcite/dolomite pourraient apporter des éléments discriminants dans la caractérisation des marbres autochtones, ce qui profitera à de futures études de provenance des marbres

Petrogenesis of mineral micro-inclusions in an uncommon carbonado

International audienc