We estimated the mineralogy of the effusive and explosive units at the Gardner shield volcano using Chandrayaan-1 Moon Mineralogy Mapper (M3) data and Lunar Reconnaissance Orbiter (LRO) Diviner data. We present a high-resolution 3D morphological map of the shield based on LRO Camera (LROC) Narrow Angle Camera (NAC) and Wide Angle Camera (WAC) images and LOLA SLDEM data. The shield shows evidence of caldera subsidence with downsag and possible trapdoor style subsidence, including a central normal fault, partially developed fault-ring structure, resurgence, and subsidence blocks, two sinuous rilles, graben, lineaments, a parasitic cone SE of the central caldera. The shield comprises 5 prominent voluminous and 10 thinner effusive basaltic flow units, and one explosive unit displaying pyroclastic material at the center of the caldera. North of the caldera is Gardner crater, which is a simple bowl-shaped impact crater, formed after the shield, revealing fresh mineralogy from the shield and highlands, including high calcium pyroxene, olivine, and Fe-spinel. The crater has a dark debris flow on its eastern wall, landslides, a boulder cluster, boulder tracs, and lineaments. The shield presents a unique lava river channel originating from a secondary oblique fault ~ 5 km wide and spreading tens of kilometers at the northern part of Mare Tranquillitatis. Our volcano-tectonic study indicates that the Gardner shield is a science rich site with exploration potential to study basaltic caldera-forming volcanoes with in-situ pyroclastic resources as it comprises almost all the major compositional and structural aspects to understand lunar thermal, tectonic, and geological evolution.

Chloride salt-bearing deposits are widely distributed across the southern highlands of Mars. Because chloride salts are highly water-soluble, these deposits may be representative of the last significant period of stable liquid water at the Martian surface. Therefore, these deposits are key to understanding the fate and evolution of surface waters on Mars. Yet, little consensus exists about the formation conditions of these deposits, and their origins remain enigmatic. This is due in part because remote spectroscopic detection and quantification of many chlorides is hampered by a lack of easily discernible diagnostic absorption features. To address this issue, we present a novel Hapke radiative transfer model (RTM)-based method to estimate hydration states and salt abundances of Martian chloride salt-bearing deposits using visible/near-infrared (VNIR) reflectance spectra. VNIR laboratory spectra are used to derive water abundances of analog chloride-bearing materials, establishing an experimental basis for application of these methods to Mars. These methods are then applied to orbital Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data to create maps of hydration state and modeled salt abundance of chloride-bearing deposits. When overlain onto high resolution 3D digital terrain models (DTMs), these methods produce the highest resolution, site-specific salt abundance maps currently available, enabling new discoveries and understanding of geologic context. As an example, deposits in the Terra Sirenum region are observed to have higher estimated salt abundances than previously recognized, exhibiting spatial variations in both abundance and surface morphology.

Mid-infrared (MIR) spectroscopy has been used with great success to quantitatively determine the mineralogy of geologic samples. It has been employed in a variety of contexts from determining bulk composition of powdered samples to spectroscopic imaging of rock thin sections via micro-FTIR. Recent advances allow for IR measurements at the nanoscale. Near field nanoscale infrared imaging and spectroscopy with a broadband source (nano-FTIR) enable understanding of the spatial relationships between compositionally distinct materials within a sample. This will be of particular use when analyzing returned samples from Bennu and Ryugu, which are thought to be compositionally like CI or CM2 carbonaceous chondrites. Returned samples will likely contain olivine/pyroxene chondrules that have been transformed into hydrous phyllosilicates, sulfides, carbonates, and other alteration phases. The use of near-field infrared techniques to probe the boundaries between once pristine chondrules and alteration phases at the nanoscale is a novel approach to furthering our understanding of the compositional evolution of carbonaceous asteroids and the processes that drive their evolution. Here we report the results of nano-FTIR spectroscopy and imaging measurements performed on the carbonaceous chondrite Allan Hills (ALH) 83100 (CM1/2). We show with nanoscale resolution that spatially resolved Fe-Mg variations exist within the phylosilicates around a chondrule rim. We also present effects of crystal orientation on the nano-FTIR spectra to account for the spectral differences between the meteorite and mineral spectra.