![Left: Average ocean fraction, calculated assuming a seawater freezing point of −1.8°𝐶 for Cases 1 and 3 and 0°𝐶 for Case 2. White shows the ice, and blue ocean. Middle: The mean near-surface air temperatures. Shown within the black contours are the regions where these vary between above and below freezing over the course of a single Earth year. Right: The mean surface temperatures. Also shown within the black contours are the regions where these vary between above and below freezing over the course of a single Earth year: these regions are narrower than the air ‘perifreezing zone’.-- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/09/Sea-Ice.png?fit=1200%2C676&ssl=1)
[astro-ph.EP] Water worlds with potential deep oceans are at the forefront of currently observable exoplanetary habitability.
The standard requirements for habitability are the presence of an energy source, a source of nutrients, and a solvent, all of which can be met in exoplanets with deep liquid water oceans. Such planets may be numerous, ranging from hycean worlds and ocean worlds to terrestrial-size planets with enhanced water content.
However, abiogenesis requires additional conditions, namely a mechanism to accumulate nutrients to the high concentrations required for prebiotic chemistry, and an energy source to drive the chemistry.
A deep ocean, and in some cases the high-pressure ice layers underneath, has traditionally been thought to prevent the required concentrations. Here we outline a location where nutrients could be concentrated in sufficiently high quantities to make abiogenesis possible — at the interface between the open ocean and the surface ice shelf.
Using a 3D General Circulation Model, we explore cases corresponding to several candidate habitable exoplanets which might have dayside sea ice. We discuss how the planet’s climate influences the nature and behaviour of the sea ice.
We investigate the ability of small-scale ice formation and melting processes to concentrate nutrients to prebiotically useful levels, and also explore the potential for meteoritic impactor fragments to provide a platform for prebiotic chemistry.
We find that both of these mechanisms may plausibly provide concentrated chemical feedstock for prebiotic chemistry, which adds an important new perspective when evaluating the prospects of habitability in planets with deep oceans.
Edouard F. L. Barrier, Nikku Madhusudhan, Frances E. Rigby
Comments: Accepted in MNRAS. 25 pages, 12 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2609.07818 [astro-ph.EP] (or arXiv:2609.07818v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2609.07818
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Submission history
From: Edouard Barrier
[v1] Mon, 7 Sep 2026 17:55:01 UTC (3,807 KB)
https://arxiv.org/abs/2609.07818
Astrobiology,
