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Water worlds can’t host life?

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From Science:

Why water worlds won’t host life

New research published online before print in the Monthly Notices of the Royal Astronomical Society shows that Earth-sized water worlds are habitable only in a very limited range of temperatures—from about 0̊C to 127̊C. Anything outside that range, which tends to occur on planets that are in a “Goldilocks zone” of 102 million to 140 million miles away from their stars (Earth is about 93 million miles away from the sun), could be devastating for life as we know it. More.

Here’s the abstract:

The unstable CO2 feedback cycle on ocean planets Ocean planets are volatile-rich planets, not present in our Solar system, which are thought to be dominated by deep, global oceans. This results in the formation of high-pressure water ice, separating the planetary crust from the liquid ocean and, thus, also from the atmosphere. Therefore, instead of a carbonate–silicate cycle like on the Earth, the atmospheric carbon dioxide concentration is governed by the capability of the ocean to dissolve carbon dioxide (CO2). In our study, we focus on the CO2 cycle between the atmosphere and the ocean which determines the atmospheric CO2 content. The atmospheric amount of CO2 is a fundamental quantity for assessing the potential habitability of the planet’s surface because of its strong greenhouse effect, which determines the planetary surface temperature to a large degree. In contrast to the stabilizing carbonate–silicate cycle regulating the long-term CO2 inventory of the Earth atmosphere, we find that the CO2 cycle feedback on ocean planets is negative and has strong destabilizing effects on the planetary climate. By using a chemistry model for oceanic CO2 dissolution and an atmospheric model for exoplanets, we show that the CO2 feedback cycle can severely limit the extension of the habitable zone for ocean planets. (paywall) – D. Kitzmann1,?, Y. Alibert1,?,†, M. Godolt2, J. L. Grenfell2, K. Heng1, A. B. C. Patzer3, H. Rauer2,3, B. Stracke2 and P. von Paris4,5

See also: Don’t let Mars fool you. Those exoplanets teem with life!

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One Reply to “Water worlds can’t host life?

  1. 1
    mahuna says:

    A. ” The atmospheric amount of CO2 is a fundamental quantity for assessing the potential habitability of the planet’s surface because of its strong greenhouse effect”

    Well, no.

    1. The greenhouse effect of CO2 is not linear, and so a doubling of atmospheric CO2 does not double the atmosphere’s ability to trap heat.

    2. Water vapor (aka “clouds”) is much more effective than CO2 in trapping heat.

    But if the entire crust of the planet is covered by solid “high pressure” ice (which I assume does NOT float), the last of your worries is the air temperature at 10,000 feet.

    B. “habitable only in a very limited range of temperatures—from about 0?C to 127?C”

    Um, 50 degrees F above boiling is “habitable”? Research on extremophiles on Earth has concluded that the tiny little critters living in hellish environments originated in the same environments as all other Life and then “migrated down”. You can’t START Earthlike life in extreme environments. Although I guess the Designer could cobble together a beastie that loves subzero temperatures and acid if the Designer chose.

    What does this suggest about the likelihood of Europa also being dead?

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