Gale crater, geological context of the rover traverse and samples studiedThe Curiosity rover landing site is located at -4.59° S, 137.44° E). Fig. S1a shows a portion of the THEMIS IR nighttime mosaic of Bradbury Rise. The landing site is marked by a black cross within the landing ellipse. It is located at a distal portion of the alluvial fan stretching below Peace Vallis on the northern rim of Gale crater.Mafic and light-toned igneous float rocks were initially observed by the Curiosity rover close to the Bradbury landing site from sol 1 to 55 in the Hummocky plain unit. After Curiosity left the fluvio-lacustrine deposit of Yellow Knife Bay (sol 55-326), it traversed back across the hummocky unit (Fig. S1b). An increasing number of light-toned rocks dominated by feldspars (porphyritic, felsic coarse-grained, felsic fine-grained) together with three groups of mafic rocks were observed along the traverse from sol 326 to sol 550. The mafic rocks are described in detail in Cousin et al. (2015) 43 and Sautter et al. (2014) 45 . The rocks selected for the present study are summarized in Table S1. Laser-Induced Breakdown Spectrometer (LIBS) spectraChemCam's laser-induced breakdown spectrometer (LIBS) uses a pulsed laser to ablate targets up to ≈ 7 m from the rover. The size of the laser interaction varies with distance, ranging from 350 µm at 1.5 m to 550 µm at 7 m 36 . The light emitted by the ablated plasma spark is collected by the same telescope used to transmit the laser beam, and is analyzed by three spectrometers which record the atomic emission spectrum over the ultraviolet (UV: 240.1-342.2nm), violet (VIO: 382.1-469.3 nm), and visible to near-infrared (VNIR: 474.0-906.5 nm) ranges 21, 22 . The ChemCam LIBS spectra consist of 6144 channels covering the above wavelength range in wavelength with typically several hundred emission peaks covering all of the major elements and many minor and trace elements.A typical ChemCam LIBS observation involves the analysis of multiple locations on the target: common geometries for LIBS observations are square grids (e.g. 3×3, 4×4) and

[1] Textural and compositional analyses using Chemistry Camera (ChemCam) remote microimager and laser-induced breakdown spectroscopy (LIBS) have been performed on five float rocks and coarse gravels along the first 100 m of the Curiosity traverse at Bradbury Rise. ChemCam, the first LIBS instrument sent to another planet, offers the opportunity to assess mineralogic diversity at grain-size scales (~100 μm) and, from this, lithologic diversity. Depth profiling indicates that targets are relatively free of surface coatings. One type of igneous rock is volcanic and includes both aphanitic (Coronation) and porphyritic (Mara) samples. The porphyritic sample shows dark grains that are likely pyroxene megacrysts in a fine-grained mesostasis containing andesine needles. Both types have magnesium-poor basaltic compositions and in this respect are similar to the evolved Jake Matijevic rock analyzed further along the Curiosity traverse both with Alpha-Particle X-ray Spectrometer and ChemCam instruments. The second rock type encountered is a coarse-grained intrusive rock (Thor Lake) showing equigranular texture with millimeter size crystals of feldspars and Fe-Ti oxides. Such a rock is not unique at Gale as the surrounding coarse gravels (such as Beaulieu) and the conglomerate Link are dominated by feldspathic (andesine-bytownite) clasts. Finally, alkali feldspar compositions associated with a silica polymorph have been analyzed in fractured filling material of Preble rock and in Stark, a putative pumice or an impact melt. These observations document magmatic diversity at Gale and describe the first fragments of feldspar-rich lithologies (possibly an anorthosite) that may be ancient crust transported from the crater rim and now forming float rocks, coarse gravel, or conglomerate clasts.

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<p>VERITAS is a proposed Discovery mission concept, currently in Step 2 (Phase A), and would launch in 2026. VERITAS addresses one of the most fundamental questions in rocky planetary evolution: why did twin planets follow different evolutionary paths? Venus’ hot lithosphere may be a good analog for early Earth, and could be responsible for the apparent lack of plate tectonics.  Determining the factors that lead to the initiation of plate tectonics would inform our predictions for rocky Earth-sized exoplanets.  VERITAS answers key questions about Venus’ geologic evolution and searches for current activity and evidence for past or present water.</p> <p><strong>Payload:</strong> VERITAS carries two instruments and conducts gravity science. The VISAR X-band [Hensley et al., this meeting] measurements include: 1) a global digital elevation model (DEM) with 250 m postings, 5 m height accuracy, 2) Synthetic aperture radar (SAR) imaging at 30 m horizontal resolution globally, 3) SAR imaging at 15 m resolution > 20% of the surface and 4) surface deformation from RPI at 2 mm precision for at least 12 targeted, potentially active areas. VEM [Helbert et al., this meeting] would produce surface coverage of most of the surface in 6 NIR bands located within 5 atmospheric windows and of 8 atmospheric bands for calibration and water vapor measurements. VERITAS would use Ka-band uplink and downlink to create a global gravity field with 3 mgal accuracy / 160 km resolution.</p> <p><strong>Science:</strong> VERITAS looks for the chemical fingerprint of past water in the form of low Fe, high Si rock in the tessera plateaus [Dyar et al. submitted, 2020; Helbert et al., submitted, 2020] and for present day volcanic outgassing of volatiles in the form of near surface water outgassing due to recent or active volcanism. </p> <p>VERITAS uses a variety of approaches to search for present day activity, including 1) tectonic and volcanic cm-scale surface deformation, 2) chemical weathering, 3) thermal emission from recent or active volcanism, 4) topographic or surface roughness changes, and 5) comparisons to past mission data sets.</p> <p>VERITAS constrains rocky planet evolution via: 1) examining the origin of tesserae plateaus -possible continent-like features, 2) assessing the history of volcanism, 3) looking for evidence of prior tectonic or impact features buried by volcanism, and 4) determining the origin of tectonic features such as huge arcuate troughs that have been compared to Earth’s subduction zones.</p> <p>VERITAS gravity data (resolution 160 km, 3x better than avg. Magellan resolution), would enable estimation of elastic thickness (a proxy for thermal gradient) and determination of core size [Mazerico et al. Fall AGU 2019].</p> <p> </p> <p><strong>Conclusions</strong>: VERITAS would create a rich data set of high-resolution topography, imaging, spectroscopy, and gravity. These co-registered data would be on par with those acquired for Mercury, Mars and the Moon that have revolutionized our understanding of these bodies. In addition to answering fundamental science questions, VERITAS’ data would motivate further Venus missions.  Active surface deformation would promote a seismic mission. Accurate topography plus surface rock type would optimize targeting of surface or areal missions.</p> <p><em>Acknowledgements</em>: A portion of this research was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The information presented to about the VERITAS mission concept is pre-decisional and is provided for planning and discussion purposes only.</p>

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