Surface topographic impact of subglacial water beneath the south polar ice cap of Mars

• Main Authors: Arnold, Neil, Butcher, Frances, Conway, Susan, Gallagher, Colman, Balme, Matthew
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Research 2022
• Subjects: 5109 Space Sciences; 5107 Particle and High Energy Physics; 5101 Astronomical Sciences; 51 Physical Sciences; Ice cap
• Online Access: https://www.repository.cam.ac.uk/handle/1810/340196; https://doi.org/10.17863/CAM.87621

Bright radar reflections observed at the Ultimi Scopuli region of Mars’ south polar layered deposits (SPLD) by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument have been interpreted as the signature of areas of subglacial water beneath it. However, other studies put forward alternative explanations that do not imply the presence of liquid water. Here we shed light on the issue by looking at the surface topography of the region. On Earth, reduced or absent basal friction, and consequent ice velocity changes, cause a distinct topographic signature over subglacial lakes. Using Mars Orbiter Laser Altimeter |(MOLA) data, we identify and characterise an anomaly in the surface topography of the SPLD overlying the area of the putative lakes, similar to those found above terrestrial subglacial lakes of similar size. Ice flow model results suggest comparable topographic anomalies form within 0.5 – 1.5 Myr with locally elevated geothermal heating or 2 – 5 Myr without elevated geothermal heating. These findings offer independent support for the presence of basal water beneath Ultimi Scopuli and suggest surface topography could supplement radar returns to help identify other potential subglacial water bodies. European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 787263)