Water‐Ice Exposing Scarps Within the Northern Midlatitude Craters on Mars

Abstract

We report new exposures of water ice along the scarps wall located within craters in the northern midlatitude region of Mars using high‐resolution imagery and spectral data of Mars Reconnaissance Orbiter. The exposed water‐ice deposits are shallower and exhibit 1.5 and 2 μm absorption. These scarps are located on the pole‐facing walls and equator‐facing wall origin floor deposits which formed over the latitude dependent mantle. Our observations advance in bracketing the younger ice deposits through the crater size‐frequency distributions of host craters, which formed around ~25 and ~95 Myr and exposed around ~1 Myr. This reveals that ice transportation, accumulation, compaction, and ice‐dust mixing occurred in recent epochs. Our study complements the earlier studies that shallow water ice is spatially widespread and consistent with subsurface water‐ice detection by neutron spectrometer. We interpret the ice remnants likely to preserve in craters pole‐facing wall and equator‐facing wall‐associated floor deposits, which demonstrates widespread water‐ice resources on Mars.

Identification of a new spectral signature at 3 μm over martian northern high latitudes: Implications for surface composition

“…Black dotted lines correspond to wavelengths of 1.5, 2.0, 3.03, and 3.62 µm. (Carrozzo et al, 2009;Vincendon et al, 2010;Harish et al, 2020) exhibit a 1.5 µm absorption of a few percent depth along with a stronger 2 µm absorption feature, while we do not detect these features. Very small water ice particles are needed to produce a 3 µm band without detectable feature at = 1.5 µm: an optical path length of only 4 µm within ice is supposed to be sufficient for OMEGA to detect ice at = 1.5 µm according to Vincendon et al (2010).…”

“…When some subsurface water ice was exposed in a trench dug by the Phoenix robotic arm, observations showed that it quickly sublimated (Arvidson et al, 2009), so permafrost is unstable at the surface. However, local exposure of pergelisol outcrops have been reported in the northern mid-latitudes on pole-facing slopes (Dundas et al, 2018;Harish et al, 2020;Dundas et al, 2021). These are subpixel compared to OMEGA resolution, and we could expect such subsurface ice exposures to be more frequent in the northern high latitudes.…”

Widespread Exposures of Extensive Clean Shallow Ice in the Midlatitudes of Mars

“…Some smaller and less well-defined exposures are included here, but more probably remain to be discovered. The two scarps reported by Harish et al (2020) were independently identified by our survey, supporting its effectiveness in identifying scarps at these scales.…”

“…CRISM data confirm exposed ice at several scarps (Table S1) beyond those described in Dundas et al (2018). Detections at two of the scarps were independently confirmed by Harish et al (2020). Notably, one observation of the icy scarp at 57°N, 95.7°E (northern scarp site #4) shows a distinct water ice signature, DUNDAS ET AL.…”

“…These surface-mantling deposits are now widely thought to have been deposited as mixtures of snow or frost and dust (in unknown and probably variable proportions) within the last few million years during periods when Mars' axial tilt was higher than at present (e.g., Head et al, 2003;Madeleine et al, 2014;Mustard et al, 2001;Schon et al, 2009). Dundas et al (2018) documented seven scarp exposure sites in the southern hemisphere and one cluster in Milankovič crater in the north; Harish et al (2020) reported two additional scarps in the northern hemisphere. However, neither conducted a comprehensive survey.…”