Bonestell Crater in Acidalia Planitia and a similar to 13 km-diameter crater to the northwest preserve geomorphic and thermophysical evidence of Amazonian-aged glacial activity. In Bonestell, lobate deposits along the northwestern rim and a cirque-like depression along the southeastern rim display steep scarps, lineated textures, and polygonal surface patterns consistent with debris-covered ice and periglacial modification. The cirque depression contains thrust-like ridges and compressional structures resembling terrestrial glacial cirques, interpreted as a remnant of polythermal glaciation, where cold- and warm-based ice likely coexisted. Thermal inertia values across these deposits range from similar to 300 to 800 JM-2 K-1s-1/2, suggesting a downslope transition from poorly consolidated sediment to indurated material. CRISM spectra reveal hydrated minerals and altered silicates consistent with episodic basal melting or volatile-driven alteration. In contrast, the unnamed northwest crater hosts clear examples of rock glaciers. Multiple lobate flows descend from alcoves along the crater walls, exhibiting convex-upward profiles, degraded termini, and compressive ridges that closely resemble terrestrial debris-covered glaciers. HiRISE image data show flow-parallel lineations and banding indicative of internal deformation and sublimation-driven modification. Spectral unmixing of THEMIS ROTO data acquired from multiple viewing geometries fit modeled mixtures of sand and indurated crust with thermal inertia values similar to 600 JM-2 K-1s-1/2, consistent with debris-coated ice. These results demonstrate that mid-latitude ice in the region is preserved in diverse forms, including cirques, rock glaciers, and debris-mantled ice masses. Their co-occurrence indicates that Amazonian glaciation was not singular nor isolated but regionally extensive and capable of producing transient wet-based conditions that locally sustained liquid water and habitable environments.

Until recently, the influence of basal liquid water on the evolution of buried glaciers in Mars' mid latitudes was assumed to be negligible because the latter stages of Mars' Amazonian period (3 Ga to present) have long been thought to have been similarly cold and dry to today. Recent identifications of several landforms interpreted as eskers associated with these young (100s Ma) glaciers calls this assumption into doubt. They indicate basal melting (at least locally and transiently) of their parent glaciers. Although rare, they demonstrate a more complex mid-to-late Amazonian environment than was previously understood. Here, we discuss several open questions posed by the existence of glacier-linked eskers on Mars, including on their global-scale abundance and distribution, the drivers and dynamics of melting and drainage, and the fate of meltwater upon reaching the ice margin. Such questions provide rich opportunities for collaboration between the Mars and Earth cryosphere research communities.

Geomorphic and mineralogical data from the martian surface indicate liquid water was abundant on the martian surface and near subsurface ∼3.5 to 4 Gyr ago, but whether early Mars had a warm and wet climate or whether it was cold and icy with punctuated periods of warmth is still unknown. Mineral assemblages of sedimentary rocks on Mars help determine past aqueous conditions and sediment sources. Here, we report on the primary and secondary mineral and amorphous assemblage of glacial flour from Collier Glacier valley on the northern flank of North Sister in Oregon, U.S.A. to identify mineralogical characteristics of mafic sediments altered under cold, wet conditions. Collier glacial flour is dominated by primary igneous minerals (plagioclase is dominant, with lesser amounts of pyroxene and olivine) and comprises 10-40 wt.% X-ray amorphous materials. Crystalline secondary phases (e.g., phyllosilicates, zeolite) are not significant contributors to the authigenic alteration assemblage. High-resolution transmission electron microscopic observations of the <2 μm size fraction of the flour demonstrate that the X-ray amorphous materials are both primary (i.e., volcanic glass) and secondary in nature. The secondary X-ray amorphous materials are enriched in Si, Al, and Fe, and we observe incipient phyllosilicate formation associated with primary and secondary amorphous materials. Our results indicate chemical weathering on a cold and icy early Mars would have produced X-ray amorphous materials, but not crystalline secondary phases. We suggest that the abundant X-ray amorphous materials recognized from orbit and in situ on Mars could have formed under cold and periodically wet conditions similar to those on North Sister today. Furthermore, the lack of volumetrically significant phyllosilicate formation in Collier Glacier flour indicates phyllosilicates on Mars did not form in a cold and wet climate.

The natural chemical and physical variations that occur within volcanic rocks (petrology) provide critical insights into mantle and crust conditions on terrestrial bodies. Visible/near-infrared (VNIR; 0.3-2.5 mu m) and thermal infrared (TIR; 5-50 mu m) spectroscopy are the main tools available to remotely characterize these materials from satellites in orbit. However, the accuracy of petrologic information that can be gained from spectra when rocks exhibit complex variations in mineralogy, crystallinity, and microtexture occurring together in natural settings is not well constrained. Here, we compare the spectra of a suite of volcanic planetary analog rocks from the Three Sisters Volcanic Complex, Oregon to their mineralogy, chemistry, and microtexture from X-ray diffraction, X-ray fluorescence, and electron microprobe analysis. Our results indicate that TIR spectroscopy is an effective petrologic tool in such rocks for modeling bulk mineralogy, crystallinity, and mineral chemistry. Given a library with appropriate glass endmembers, TIR modeling can derive glass abundance with similar accuracy as other major mineral groups and provide first-order estimates of glass wt.% SiO2 in glass-rich samples, but cannot effectively detect variations in microtexture and minor oxide minerals. In contrast, VNIR spectra often yield non-unique mineralogic interpretations due to overlapping absorption bands from olivine, glass, and Febearing plagioclase. In addition, we find that sub-micron oxides hosted in transparent matrix material that are common in fine-grained extrusive rocks can lower albedo and suppress mafic absorption bands, leading to very different VNIR spectra in rocks with the same mineralogy and chemistry. Mineralogical interpretations from VNIR spectra should not be treated as rigorous petrologic indicators, but can supplement TIR-based petrology by providing unique constraints on oxide minerals, microtexture, and alteration processes.

We discuss how a Code of Conduct-type policy can foster a safer and more equitable environment within mission teams and research groups, as well as professional societies and conferences/meetings.Such a policy is highly complementary to other common Rules of the Road-type policies for NASA and NSF-funded science endeavors, and can be instrumental in creating a more inclusive culture.Eight recommendations are provided to increase effectiveness of Code of Conducttype

Glaciated environments are important sources of lithogenic nutrients due to mechanical and chemical weathering and meltwater transport influencing downstream ecosystems. High physical weathering rates in subglacial environments due to bedrock grinding results in significant chemical weathering due to increased reactive mineral surface area. Until recently, glaciers and ice sheets were considered a minor part of the global Si cycle, in part because near-freezing conditions were thought to limit silicate weathering rates. However, recent research has shown that silicate dissolution is the predominant chemical weathering process in alpine glaciated catchments in the volcanoes of the Cascades Range, USA [1]. Alpine glacier systems may provide large fluxes of bioavailable Si similar to other recent findings [2,3

This paper emphasizes the importance of using terrestrial analogues to improve our understanding of the role of ice on Mars through its associated landforms. We discuss terrestrial regions and techniques that can help understand Martian icy environments, and highlight the necessity to explore the Martian cryosphere as the next natural step.

Liquid water was abundant on early Mars, but whether the climate was warm and wet or cold and icy with punctuated periods of melting is still poorly understood. Modern climate models for Mars tend to predict a colder, icier early climate than previously imagined. In addition, ice and glaciation have been major geologic agents throughout the later Hesperian and Amazonian eras. One process that can act in such climates is repeated freezing and thawing of water on the surface and in the subsurface, and is significant because it can occur anywhere with an active layer and could have persisted for a time after liquid water was no longer stable on Mars’ surface. As freeze-thaw is the dominant mechanical weathering process in most glacial/periglacial terrains, it was likely a significant geomorphologic driver at local to regional scales during past climates, and would potentially have been most active when day-average surface temperatures exceeded 0 °C for part of the year. Indeed, freeze-thaw involving liquid water in the Amazonian is evidenced by abundant geomorphic features including polygonal ground and solifluction lobes requiring seasonal thawing. In addition to physical modification, freezing can drive solutions towards supersaturation and force dissolved solutes out as precipitates. In Mars-like terrains, dissolved solutes are typically dominated by silica. In polar regions on Earth, freeze-thaw cycles have been shown to promote deposition of silica, and freeze-thaw experiments on synthetic solutions found stable amorphous silica that built up over multiple cycles. Freeze-thaw may therefore be an important but overlooked chemical weathering process on Mars. However, our ability to assess its impact on alteration of martian terrains is majorly limited by the current lack of understanding of the alteration phases produced (and formation rates) under controlled freeze-thaw weathering of Mars-relevant materials. To address this knowledge gap, we report results from (1) freeze-thaw weathering products found at a glacial Mars analog site at the Three Sisters, Oregon, and (2) new controlled freeze-thaw experiments on basaltic material.

Liquid water was abundant on early Mars, but whether the climate was warm and wet or cold and icy with punctuated periods of melting is still poorly understood. Modern climate models for Mars tend to predict a colder, icier early climate than previously imagined [e.g., 1]. However, any model for the early climate on Mars must be reconciled with the chemical record. We currently do not understand how alteration mineralogy formed in snow and ice dominated conditions compares to that of warmer climates, and it is unclear whether cold climate weathering could form all or any of the aqueous alteration phases expressed on early martian surfaces [2]. To help resolve this knowledge gap, we synthesize results from glacial Mars analog sites at the Three Sisters, Oregon and mafic regions of the Antarctic ice sheet, and compare them to the surface mineralogy of Mars. These sites provide the opportunity to investigate weathering in environments analogous to glacial environments on Mars throughout geologic time, including snowpacks or smaller wet-based or polythermal glaciers [3, 4] as well as the proposed extensive ice sheets of the late Noachian icy highlands model

Volcanic surfaces are common and varied throughout the terrestrial planets. Remote spectroscopy is often the only method for determining surface chemistry and mineralogy of such provinces, and is thus critical for understanding petrologic processes and constraining planetary interior evolution and chemistry. Natural volcanic systems exhibit variability in magmatic chemical evolution, crystallinity, oxidation, and eruption-related alteration (e.g. hydrothermal). The extent to which spectroscopy can identify these characteristics alongside each other is thus a key question for interpreting volcanic processes from orbit. While the effects of each of these on visible/near infrared (VNIR) and thermal infrared (TIR) spectra of igneous rocks has been studied separately to varying degrees, their combined spectral effects (and interpretability of such spectra) are understudied.

past 100 years, exposing fresh subglacial/proglacial sediment, with annual ice/snowmelt feeding the proglacial lake. Mineralogical Signatures Of Cold And Icy Climates On Ancient And Modern Mars. N. A. Scudder, B. Horgan, A. Rutledge, E. B. Rampe, R. J. Smith, J. Graly, Purdue University (nscudder@purdue.edu), Northern Arizona University, NASA Johnson Space Center, Stony Brook University, Indiana University Purdue University Indianapolis.

Introduction: New results show that cold-climate silica mobility is more efficient than previously reported, and is the dominant weathering process in glaciated mafic bedrock. Based on field work at glaciated volcanic sites, we hypothesize that this is due to both high rates of silica dissolution from mafic bedrock and reprecipitation of silica in the form of opaline silica coatings and other poorly crystalline silicate alteration phases in proglacial sediments. Widespread evidence for past and present-day glaciation on Mars [1-4] means that this cycle must be investigated in order to better interpret alteration signatures on the surface of Mars, especially those in the north polar deposits [5-7]. Amorphous silica in this settings could be interpreted as mineralogical evidence for alteration by meltwater sourced from ice or snow. Field study: To investigate meltwater-driven silica cycling on mafic volcanic bedrock, water and rock samples were collected during June 2015 and July 2016 from glaciated volcanic bedrock in the Cascade Volcanic Arc: Mount Adams (46o9’N, 121o27’W), Mount Hood (45o21’N, 121o42’W), Middle Sister (44o9’N, 121o46’W) and North Sister (44o10’N, 121o47’W). Dominant bedrock compositions for each site are detailed in Table 1. Evidence for subglacial precipitation of poorly crystalline silica was found at North and Middle Sisters in the form of striated rock coatings on recently deglaciated lava flows (Fig 1) [8] and in a silica-enriched poorly crystalline component of glacial flour from proglacial till deposits [9]. Results: Figure 1 shows a representative thermal infrared spectrum of a rock coating from the North Sister proglacial plain. It exhibits similar absorptions to opaline silica and an Al-Si gel, indicating that it is composed primarily of poorly crystalline silica. Figure 2 shows the mean glacial outwash stream silica concentrations. The mafic bedrock sites have greater concentrations of silica in glacial outwash waters compared to the felsic sites. Within each mafic field site, the highest silica concentrations were measured in moraine-sourced springs. Silica cycling in terrestrial glacial systems The high rate of bedrock comminution in subglacial environments results in high rates of both chemical and physical weathering, due to the increased reactive mineral surface area formed through glacial grinding. In most bedrock types, carbonate weathering is enhanced and silica fluxes are depressed in glacial outwash compared with global average riverine catchment runoff due to low temperatures and short residence times [10]. However, in mafic systems, higher dissolved SiO2 concentrations have been observed [11-13]. Additionally, remote sensing has identified high-silica zones in proglacial outwash plains on mafic bedrock [14]. Water composition. The major difference between glacial alteration of volcanic bedrock and more typical continental terrains is the absence of significant dissolved carbonate in the former. In the absence of carbonate minerals which normally dominate dissolution processes at glacier beds [10], carbonation of feldspar can become the dominant weathering process [11]:

The glaciers of the Three Sisters volcanoes in Cascadia have retreated dramatically over the past century. In order to understand ongoing chemical weathering and solute transport in the proglacial valleys, waters were sampled from glacier outwash streams, local snowmelt, and proglacial springs and lakes at Collier and Diller Glaciers. To understand weathering and transport processes in the proglacial plains, infrared orbital remote sensing data was used to map compositional variability and highlight weathering products, which were then ground-truthed with laboratory mineralogical and chemical analyses of sediments. The hydrochemistry is significantly affected by a sub- and proglacial mafic weathering system lacking carbonate minerals. Here we report major ion concentrations in meltwaters for the summer 2016 and 2017 melt seasons. Total cation concentrations range from 3 to 250 μeq/l and dissolved bicarbonate concentrations range from 2 to 200 μeq/l. Other dissolved anions are negligible compared to bicarbonate. Dissolved silica concentrations range from 2 to 260 μmol/l, comparable to total dissolved cation concentrations. The highest cation and silica concentrations were measured in moraine-sourced springs. Compositional remote sensing analysis identified alteration zones in the proglacial plains at both Collier and Diller indicating potential hydrated silica. This analysis is consistent with laboratory analysis of sediment samples, which indicate the presence of poorly crystalline phases weathering products, including hydrated silica. Weathered materials are preferentially deposited on moraines due to aeolian and glacial transport, as well as intra-moraine alteration, and at abandoned stream terraces due to fluvial transport. Geochemical measurements indicate that the predominant form of chemical weathering in these periglacial mafic systems is the carbonation of feldspar as well as reactive volcanic glass. The presence of poorly crystalline silicates, as indicated by remote sensing datasets and laboratory analysis, is consistent with rapid weathering of feldspars and glass and formation of Fe-Al-Si-bearing mineraloids in these proglacial valleys. This weathering regime has wide-ranging implications for atmospheric CO2 drawdown due to cold-climate volcanic rock weathering.