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HiRISE Observations of Martian Ground Ice: A Possible Resource for Exploration


Ground ice is widespread on Mars and has been studied with a variety of techniques [1-2], including in situ exploration [3]. Model estimates bound the likely spatial distribution [4]. The widespread occurrence makes it a potential resource for future exploration [5]. Important variables for both scientific interpretation and use as a resource include the depth to ice, ice content, and vertical structure. The High Resolution Imaging Science Experiment (HiRISE) onboard the Mars Reconnaissance Orbiter has been acquiring high-resolution (0.25–0.6 cm/pix) images of Mars since 2006. These images provide several new avenues to understand ground ice.

New impact craters expose ice at middle and high latitudes. These craters reveal the geographic distribution of ice, which is exposed at latitudes as low as 39° N, and demonstrate that it occurs at depths <1 meter. The ice remains bright for months or years, despite sublimation. Thus, the ice at these locations has a low lithic content, although some clean ice could be produced by the impact process.

Erosional scarps found near 55°N/S provide cross-sections through ice, confirmed by infrared spectra. At these sites, massive ice occurs within 1–2 meters of the surface, and can be >100 m thick. The scarps bound pits several km across, eroding mantling deposits likely formed from snow and dust. This provides important insight into past Martian climate. Boulders on the surface could have been transported by glacial flow, impact gardening, or cryoturbation processes, but remain poorly understood.

These observations provide key high-resolution data, showing that ice deposits on Mars can be shallow, clean, and thick, and that the ice may be widely available, although HiRISE observations are restricted to a few locations. These sites are targets for future scientific investigation and show that Martian ice deposits have many properties that would allow use as a resource by human explorers if Planetary Protection requirements are met. Important remaining unknowns include the extent of lateral heterogeneities and the concentration of dust, salts, and other contaminants.

[1] Feldman W. C. et al. (2008), in The Martian Surface (J. F. Bell, ed.). [2] Mouginot J. et al. (2010) Icarus, 210, 612-625. [3] Mellon M. T. et al. (2009) JGR, 114, doi:10.1029/2009JE003417. [4] Mellon M. T. et al. (2004) Icarus, 169, 324-340. [5] Abbud-Madrid et al. (2016) M-WIP study report, posted at http://mepag.nasa.gov/reports/.