Europa, extreme shrimp, and the search for alien life


“Extreme shrimp” sounds like a marketing campaign for a seafood chain.


But let’s not forget the oxygen co-fuel used by these deep sea extremophiles.

All the thermal-vent ecosystems are driven not by the metals and sulfur coming out of the vents, but by the oxidation of these oxygen-poor chemicals with oxygen carried down to the deep, from the air, by the thermohaline circulation system.

We don’t (yet) know of a similar source of oxygen on Europa.


Life on earth started out without much oxygen. Oxygen was a byproduct of bacteria which incidentally was a massive extinction event on earth.


Probably. But back then it was not around deep ocean vents. Cyanobacteria made the oxygen with avaiilable compounds such as CO2 and H2O, using energy derived from abundant sunlight.

If there’s any life on Europa, it will probably resemble whatever came before that. Not much sunlight way out there. Maybe some interesting chemicals circulating but, without either a source of photons or a set of highly energetic reactants such as S + 2O2 → SO4, it runs more slowly by several orders of magnitude.

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Thanks for this; it’s a point that often goes unappreciated. There’s an expression about fish not noticing water, and in the same way it seems like even scientists often take oxygen for granted.

So you sometimes hear about the life around heat vents not being dependent on energy from light, but really all ecosystems on earth are. If we recognize that complex molecules like sugar are really a way of transporting that energy into places that don’t receive light directly, we should recognize oxygen is really another.

I’m really not sure what alternatives there are and would love to see one explained. I’ve seen tidal heating mentioned before, but heat itself is not a form of energy you can exploit. You need a temperature gradient, and on the scale of a microbe there is not going to be anything worthwhile.

It’s true a mixture of chemicals available for reactions is supposed to have started life here, but if there’s any notable energy to extract it won’t stay that way for billions of years. This video at least gives a way around that: vents could sustain such a mixture by slowly releasing one reagent into another.

But what are these reagents supposed to be? On earth there are reducing agents like sulfide to seep from the interior, and that works because life has created a very peculiar oxidizing atmosphere. I can’t come up with why there would be such a difference in a case like Europa, and haven’t heard anything so much as suggested, which is a pretty serious omission.

I mean, I’m all for exploring the possibility of life in places like this. But it seems to me there’s a lot of simply pointing to extreme environments on earth and handwaving all the details of why they work, and it makes it hard to get excited about the chances.


I’m pretty pursuaded by the Rare Earth hypothesis which says, based on our own planet’s history, that single-cell life is probably everywhere. It may have formed just about immediately after the Earth cooled off enough to have water.

But multicellular life may be vanishingly rare. A number of highly unlikely coincidences were necessary to bring us to the place we are today. It’s possible that very few planets have the same circumstances. It would certainly resolve the Fermi paradox.


I think the bottom line is, we don’t know. Those deep-sea ecosystems do interesting things with a relatively small amount of oxygen, a chemical that comes from the surface. On Europa, you have a very gloomy ocean with an ice ‘roof’ on top of it, and lots of thermal input from the tidal forces acting on it. And the heat is a source of energy, although a poor one. Another speculative energy source would be the natural Uranium and Thorium in Europa’s core. Any life form that works out a way to harvest the alpha decay will have a marvelous source of energy. (Because nuclear forces are from four to eight orders of magnitude greater than chemical forces, this would be a very difficult problem for a biological system.)

I hope to live long enough to hear news of Europa’s ocean. So far, the Solar System has been an even more amazing and marvelous place than we humans imagined before we went out there.

Try with gamma.


I think the jury is still out on this one. Maybe, and it’s a big maybe, they derive some energy from the radiation. IMNSHO it is more likely that these microbes are merely radiation tolerant. That gives them an advantage over other microbes, but they do not actually convert radiation to organic energy in any significant way.

Enceladus probably has a better chance of hosting life, but NASA/ESA have already decided that they like Europa better. I guess after Cassini, it’s Jupiter’s turn?

Another factor, I think, is that they figured out a way to do a mission to Jupiter orbit that will work with solar panels (though not for long – they degrade in the high radiation environment). Whereas a new Saturn orbiter would require plutonium for RTGs, and the very small amount of plutonium DOE has left is already spoken for (the Mars 2020 mission).

We need to kickstart the LFTR reactors. Pu-238 (resp. Np-237) is a byproduct of their normal operations.

And in short-term we need to extract the politicos’ heads out of their rectums and force them to release money for Pu-238 production.

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