Europa’s ice ocean is the most interesting extra-terrestrial cocktail outside of the Pan-Galactic Gargle Blaster: an entire world of water and heat. It could only be more exobiologically interesting if we detected Vulcans. Active controversy fuels spirited research into this incredible environment, with one theory explaining how the ice shell coating the planet could be pumping the ocean full of oxygen.
The main subject of debate is the thickness of Europa’s icy shell, as a layer of incredibly frozen water (over one hundred degrees C below) is the sort of thing that affects everything underneath. The “thin ice” model suggests that the outer shell is only a couple of kilometers thick at most, covering an ocean continually heated by the immense tidal forces from Jupiter (a reverse of Earth’s organization, where the moon causes tides on the host planet). A thin crust means that regular fracturing and ejection regularly resurfaces the incredibly smooth surface, while still causing cracks and - most importantly - shuttling material up and down between the ice-locked ocean and the external universe.
This is particularly important because oxygen is constantly created on the surface, giving Europa a thin atmosphere (and by “thin” we mean “one trillionth the pressure of Earth’s”). This oxygen awesomely originates from charged particles from the sun and from Jupiter’s immense magnetosphere ramming into the ice and blasting it into oxygen and hydrogen. Professor Richard Greenberg of MIT thinks that this oxygen could slowly saturate the Europan ocean as the shell is continually replaced by fresh water from the submerged seas, cycling the entire surface.
Of course, oxygen isn’t essential for life - even water is only a selfish selection because we happen to be based on it - but we know for a fact water and oxygen are required for at least one manner of life (in fact it’s encoded in our existence), so such a setup on another world is incredibly interesting.
Another fortunate effect of such an ice-cycling could be the ejection of items from the subsurface world to where we could see them from space, although “fortunate” really depends on whether you’re the one looking or the thing ejected. Should any simple lifeforms suddenly find themselves on the surface, the minus one-sixty Celsius and absence of fluid environment means they wouldn’t be around to appreciate our attention.
Europa remains our most exciting extra-terrestrial life possibility, and we’ll get a better look in 2026 with the Europa Jupiter System Mission (sixteen years late for Arthur C Clarke’s 2010 deadline, but still pretty good!) The joint NASA/ESA mission will examine Europa and Ganymede, and we can eagerly anticipate incredibly interesting data. (And hope they don’t get cancelled).
Luke McKinney
Image Credit: Walter Myers
Greenberg’s Thoughts (and book)
Europa Jupiter System Mission
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