Ocean Worlds

Liquid Water On Cold Exo-Earths Via Basal Melting Of Ice Sheets

By Keith Cowing
Press Release
December 7, 2022
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Liquid Water On Cold Exo-Earths Via Basal Melting Of Ice Sheets
Schematic of a basal melting model for icy exo-Earths. (a) Due to the high surface gravity of super-Earths, ice sheets may undergo numerous phase transformations. Liquid water may form within the ice layers and at the base via basal melting with sufficient geothermal heat. If high-pressure ices are present, meltwater will be buoyant and migrate upward, feeding the main ocean. The red arrows show geothermal heat input from the planet’s rocky interior. (b) Pure water phase diagram from the SeaFreeze representation [32] illustrating the variety of phases possible in a thick exo-Earth ice sheet. Density differences between the ice phases lead to a divergence from a linear relationship between pressure and ice-thickness. — astro-ph.EP

Liquid water is a critical component of habitability. However, the production and stability of surficial liquid water can be challenging on planets outside the Habitable Zone and devoid of adequate greenhouse warming.

On such cold, icy exoEarths, basal melting of regional, global ice sheets by geothermal heat provides an alternative means of forming liquid water. Here, we model the thermophysical evolution of ice sheets to ascertain the geophysical conditions that allow liquid water to be produced and maintained at temperatures above the pressure controlled freezing point of water ice on exoEarths. We show that even with a modest, Moon like geothermal heat flow, subglacial oceans of liquid water can form at the base of and within the ice sheets on exoEarths.

Furthermore, subglacial oceans may persist on exoEarths for a prolonged period due to the billion year half lives of heat producing elements responsible for geothermal heat. These subglacial oceans, often in contact with the planets crust and shielded from the high energy radiation of their parent star by thick ice layers, may provide habitable conditions for an extended period.

Lujendra Ojha, Bryce Troncone, Jacob Buffo, Baptiste Journaux, George McDonald

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph)
Cite as: arXiv:2212.03702 [astro-ph.EP] (or arXiv:2212.03702v1 [astro-ph.EP] for this version)
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Journal reference: Nat Commun 13, 7521 (2022)
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Submission history
From: Lujendra Ojha
[v1] Wed, 7 Dec 2022 15:22:25 UTC (968 KB)

SpaceRef co-founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.