The metabotropic glutamate receptor 1 (mGluR1) is abundantly expressed in the mammalian central nervous system, where it regulates intracellular calcium homeostasis in response to excitatory signaling. Here, we describe heterozygous dominant mutations in GRM1, which encodes mGluR1, that are associated with distinct disease phenotypes: gain-of-function missense mutations, linked in two different families to adult-onset cerebellar ataxia, and a de novo truncation mutation resulting in a dominant-negative effect that is associated with juvenile-onset ataxia and intellectual disability. Crucially, the gain-of-function mutations could be pharmacologically modulated in vitro using an existing FDA-approved drug, Nitazoxanide, suggesting a possible avenue for treatment, which is currently unavailable for ataxias.

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The ancient surface of Mars is dominated by degraded impact craters with reduced or eliminated rim relief. Some degraded craters have an inlet valley, while many remain fluvially isolated. Despite controlling Martian fluvial connectivity, few constraints exist on why some—but not all—degraded craters possess inlets. We compared a suite of properties around degraded Martian craters with and without inlets to ascertain what topographic and hydrologic factors influenced inlet formation. Slope and surface roughness are similar, but topographic inset within the catchment, drainage density, and potential contributing areas diverge for breached and non‐breached craters. We suggest that the importance of basin hydrology‐related factors over topographic factors is the result of the former less frequently surpassing inlet incision thresholds than the latter. We conclude that greater topographic inset (i.e., craters deeper within regional depressions) promoted higher discharge, and that inlet valley formation was ultimately controlled by Mars' crater‐dominated topography.

Over 250 hydrologically open paleolakes, which filled with water before catastrophically breaching, have been identified on Mars. These open‐basin lakes are recognized by the topographic geometry of a closed contour below the elevation of the outlet, indicating that the lake was incompletely drained by the breach flood. Here, we explore factors that controlled how completely a given open‐basin lake on Mars drained using (a) observations of 24 open‐basin lakes on Mars and (b) numerical modeling experiments of lake breach flooding. Observational results suggest that the key parameters for promoting more complete draining in open‐basin lakes on Mars were steeper regional slopes and taller crater rims. From a suite of 303 numerical experiments, we find that more complete draining is accomplished with larger basins, steeper regional slopes, basins with steeper walls, taller crater rims, and a more erodible substrate (parameterized by grain size in our model). Outliers in the observational results suggest that complete draining was inhibited by the presence of another lake immediately downstream of the breach as well as a less erodible substrate relative to other basins. We observe no correlation between open‐basin lake area and drained fraction on Mars, contrary to the strong trend in our numerical experiments. We hypothesize that this is the result of increasing resistance to erosion with depth in the Martian crust, which is not incorporated into our model. Our results provide new insights into controls on the fluvial integration of the early Mars landscape as well as the spatially variable erodibility of the shallow Martian crust.

<p>On planetary bodies, impact craters and fluvial activity interact, and valley incision competes with the topographic, lithologic and structural disruption caused by impacts that frequently occurred in the geologic past. Yet, many terrestrial and martian impact craters were breached by inlet valleys, which supplied (or still supply on Earth) crater interiors with water. Radial and concentric drainage patterns are also observed around craters, suggesting impact-induced structure fundamentally influences incision in these areas.</p> <p>To gain a greater understanding of fluvial erosion in crater-dominated terrains, and inlet valley formation across crater rims, we will investigate the incision history of the Dhar valley inlet at Lonar Crater, Maharashtra, India. Lonar crater is the best-preserved impact crater in basalt, which formed within the last 100 ka when a bolide impacted the Deccan Traps basalts. At 1.8 km diameter and 135 m deep, it is a simple crater. A small, 5.5 m deep lake resides in the crater interior and is fed by the Dhar inlet to the north east, and groundwater springs in the crater walls. We would use cosmogenic radionuclide dating to investigate the onset and timescales of fluvial erosion that formed the inlet valley, with comparison to the surrounding non-cratered terrains. We plan to measure the accumulation of cosmogenic <sup>3</sup>He in pyroxene and olivine to derive <em>in situ</em> exposure ages at different levels in the valley, and also to derive basin-averaged denudation rates from fluvial sediments. Vesicle-fill quartz is also present, so measurement of cosmogenic <sup>10</sup>Be is a possible complement to <sup>3</sup>He measurements.</p> <p>We also plan to complete detailed mapping of the Dhar valley inlet and examine hypotheses relating to Dhar valley inlet formation. Previous authors have posited that the Dhar valley inlet formed as spring activity promoted drainage head erosion across the steep crater rim and/or that gullying concentrated in the north east of the crater due to water supply from higher elevation regions in that direction. We will also investigate whether a prominent fracture in the north east, and sub-vertical cooling fractures that trend NE-SW (an original basaltic flow feature), may have influenced the Dhar valley inlet formation.</p> <p>Increased constraints on crater inlet valley incision mechanisms, controls, and rates, will help extrapolate our understanding of fluvial erosion to crater-dominated terrains, including key specific sites such as Jezero crater on Mars, and in generalized numerical simulations of cratered landscapes. This work will ultimately help place constraints on the extent, absolute timing, environments and mechanisms required to develop fluvial valleys around and into impact craters.</p> <p>Field work is expected to be completed in early Spring 2023 and at EGU 2023 we will present preliminary findings from the field and detail our next steps moving forward. This work is possible thanks to funding from the Eugene and Carolyn Shoemaker Impact Crater Research Fund and graduate field work funding from the Jackson School of Geosciences. </p>

There is abundant evidence for liquid water on early Mars, but the debate remains whether early Mars was warm and wet or cold and icy with punctuated periods of melting. To further investigate the hypothesis of a cold and icy early Mars, we collected rocks and sediments from the Collier and Diller glacial valleys in the Three Sisters volcanic complex in Oregon. We analyzed rocks and sediments with X-ray diffraction (XRD), scanning and transmission electron microscopies with energy dispersive spectroscopy (SEM, TEM, EDS), and visible, short-wave infrared (VSWIR) and thermal-IR (TIR) spectroscopies to characterize chemical weathering and sediment transport through the valleys. Here, we focus on the composition and mineralogy of the weathering products and how they compare to those identified on the martian surface. Phyllosilicates (smectite), zeolites, and poorly crystalline phases were discovered in pro-and supra-glacial sediments, whereas Si-rich regelation films were found on hand samples and boulders in the proglacial valleys. Most phyllosilicates and zeolites are likely detrital, originating from hydrothermally altered units on North Sister. TEM-EDS analyses of the <2 um size fraction of glacial flour samples demonstrate a variety of poorly crystalline (i.e., no long-range crystallographic order) phases: iron oxides, devitrified volcanic glass, and Fe-Si-Al phases. The CheMin XRD on the Curiosity rover in Gale crater has identified significant amounts of X-ray amorphous materials in all samples measured to date. The amorphous component is likely a combination of silicates, iron oxides, and sulfates. Although we have not yet observed amorphous sulfate in the samples from Three Sisters, the variety of poorly crystalline weathering products found at this site is consistent with the variable composition of the X-ray amorphous component identified by CheMin. We suggest that these amorphous phases on Mars could have formed in a similarly cold and icy environment.