Modeled Subglacial Water Flow Routing Supports Localized Intrusive Heating as a Possible Cause of Basal Melting of Mars' South Polar Ice Cap

Abstract

The discovery of an ~20‐km‐wide area of bright subsurface radar reflections, interpreted as liquid water, beneath the Martian south polar layered deposits (SPLD) in data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument, and the discovery of two geologically recent potential eskers (landforms produced by subglacial melt) associated with viscous flow features in Martian midlatitudes, has suggested recent basal melting of Martian ice deposits may be feasible, possibly due to locally elevated geothermal heating. Locations of terrestrial subglacial lakes and major drainage axes have been successfully predicted from subglacial hydraulic potential surfaces calculated from surface topography and ice thickness. Here, we use surface topography from the Mars Orbiter Laser Altimeter and SPLD bed elevations derived from MARSIS data to calculate the subglacial hydraulic potential surface beneath the SPLD and determine whether the observed high reflectance area coincides with predicted subglacial lake locations. Given the sensitivity of terrestrial predictions of lake locations to basal topography, we derive over 1,000 perturbed topographies (using noise statistics from the MARSIS data) to infer the most likely locations of possible subglacial water bodies and drainage axes. Our results show that the high reflectance area does not coincide with any substantial predicted lake locations; three nearby lake locations are robustly predicted however. We interpret this result as suggesting that the high reflectance area (assuming the interpretation as liquid is correct) is most likely a hydraulically isolated patch of liquid confined by the surrounding cold‐based ice, rather than a topographically‐constrained subglacial lake.

The Global Search for Liquid Water on Mars from Orbit: Current and Future Perspectives

“…Modeling of the subglacial hydraulic potential beneath the South polar cap, based on radar-derived basal topography, provided estimates of the location of subglacial lakes that do not match the bright radar reflector. This finding is consistent with a hydraulically isolated liquid body confined by cold-based ice, rather than with a subglacial lake [34]. In spite of the theoretical difficulties in reconciling the presence of liquid water with the known characteristics of the SPLD, recent observations acquired by MARSIS over the same region, and analyzed using signal processing procedures commonly applied on Earth to discriminate between wet and dry subglacial areas, are in agreement with the earlier detection of subglacial water, and provide evidence for other wet areas in its surroundings, suggesting the presence of a complex hydrologic system [35].…”

Characteristics of the Basal Interface of the Martian South Polar Layered Deposits

“…The presence of subsurface liquid water was initially ruled out due to the cold temperatures expected at the base of the SPLD (Plaut et al., 2007). However, recent analyses at a few locations of bright basal reflectors suggest there may be a liquid water component at the interface (Lauro et al., 2021; Orosei et al., 2018), although the presence and stability of liquid water is under debate (Arnold et al., 2019; Sori & Bramson, 2019). Thus, key questions about the properties of the basal interface below the SPLD remain unanswered.…”

Red Sea tectonics unveil the largest known terrestrial ice stream: New constraints on Late Ordovician ice sheet dynamics

“…Our findings show that subglacial AIS-related MLs were misclassified as mega-yardangs and raise the question of whether similar misinterpretations could have been made in other parts of the arid and hyper-arid world, and possibly more so on Mars, where MLs are much less likely to be obscured or modulated by tectonic activities. Ice streams could have carved mega-lineated flutes in the Martian outflow channels during earlier warmer climatic periods on Mars 68,69 ; discoveries of liquid water beneath the Martian south polar layered deposits 70 suggest recent basal melting of Martian ice sheets 71 . The long glacial cycles due to the Earth's high amplitude obliquity modulation in the Ordovician (>10 6 yr) 14 that compared well with the Martian amplitude modulation 72,73 and the presence of the large polar landmass of Gondwana raises the suggestion that the AIS-related landforms could potentially present a better analogue to Martian glacial landforms than Quaternary landforms 74,75 .…”