http://arxiv.org/abs/1801.00748
We model the evolution of ocean temperature and chemistry for rocky exoplanets with 10-1000$\times$ Earth’s H$_2$O but without H$_2$, taking into account C partitioning, high-pressure ice phases, and atmosphere-lithosphere exchange. Within our model, for Sunlike stars, we find that: (1) habitability is strongly affected by ocean chemistry; (2) possible ocean pH spans a wide range; (3) exsolution-driven climate instabilities are possible; (4) surprisingly, many waterworlds stay habitable for $>$1 Gyr, and (contrary to previous claims) this longevity does not necessarily involve geochemical cycling.
We also find, using an ensemble of N-body simulations that include volatile loss during giant impacts, that a substantial fraction of habitable-zone rocky planets emerge after the giant impact era with deep, ice-free water envelopes. This outcome is sensitive to our assumptions of low initial abundances of $^{26}$Al and $^{60}$Fe in protoplanetary disks, plus H$_2$-free accretion. We use the output of the N-body simulations as input to our waterworld evolution code. Thus, for the first time in an an end-to-end calculation, we show that chance variation of initial conditions, with no need for geochemical cycling, can yield multi-Gyr habitability on waterworlds.
E. Kite and E. Ford
Wed, 3 Jan 2018
35/59
Comments: 23 pages, 18 figures, submitted
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