The Europa Gambit: Part II

by Paul Gilster on February 24, 2007

Most speculation about finding life on Europa revolves around drilling through the perhaps kilometers-deep ice to sample the ocean beneath. But paleobiologist Jere H. Lipps (University of California, Berkeley) envisions a different exercise. Lipps, who has studied polar environments for twelve years in Antarctica, notes that turnover of ice on that continent often brings organisms to the surface that would otherwise be hidden.

Is ice shifting similarly on Europa? Absolutely. Looking at images of that fractured surface, we see a dynamic environment where water from beneath seems to have welled up and re-frozen. The surface is strewn with domes, ridges and tilted ice rafts. Evidence of life might be found in places where blocks of ice have pushed up to form ridges and rills.

Lipps puts it this way:

“This is a paleontological search strategy, which is what I do. If I want to collect fossils in Nevada, I get a map and look for likely spots, like rock outcroppings, where fossils will be found. Ice turned on its edge is just a geologic outcrop to me let’s go there and see if we can find evidence of past or present life.”

Europa's icy surface

What about radiation in the hostile Jovian environment? Lipps believes it is unlikely to penetrate more than one or two meters. That would leave even near-surface ice environments — cracks, overhangs, and so on — that could support life forms. And just as the paleontologist in New Mexico can see an evolutionary history of life over time by studying layers of sedimentary rock, ices of different ages could provide the same perspective to a rover or — let’s hope one day — a human on Europa.

Image
: The reddish ovals in the center of this image may be areas where water from Europa’s underground ocean upwelled and froze on the surface. Credit: Galileo Project, NASA.

Lipps spoke on a panel at the American Association for the Advancement of Science meeting that included William McKinnon (Washington University), whose advocacy of a Europa mission we discussed not long ago in the first part of this post. A central point about the search for life on Europa is not to get too doctrinaire about just how and where we may find it, for Earth’s poles show life’s unique adaptability. Lipps again:

“Based on analogy with Earth’s polar seas, Europan life may occur in many habitats: on soft and rocky bottoms at the ocean’s floor, associated with hydrothermal vents on the floor of the oceans, at different levels in the water column as plankton and nekton, and in and on the ice cover itself. Some of these might contain complex associations of life forms, including both micro- and macroscopic forms and consumers and predators.”

Lipps and Sarah Rieboldt proposed likely habitats for Europan life in “Habitats and taphonomy of life on Europa,” Icarus 177 (2005), pp. 515-527. Taphonomy refers to the processes that occur during fossilization, a necessary study if paleontologists are to extract accurate information about the organisms involved. Some day let’s hope we have boots on the ground on Europa to pursue these investigations, but a sampling strategy could be created earlier for properly equipped rovers.

Darnell Clayton February 24, 2007 at 15:29

Color me skeptical, but I doubt we will find anything larger than a single celled micro-organism, if we find anything at all.

Sunlight would have a difficult time filtrating through the 20 mile ice crust (give or take several miles or more) which means unless these organisms find something salty (aside from each other) there might not be much to view beneath the crust.

Chris Wren February 24, 2007 at 17:18

Isn’t Europa bathed in Jovian radiation? I can definitely see a robotic mission, but “boots on the ground” seems kind of improbable.

Administrator February 24, 2007 at 17:55

Chris, sure, my ‘boots on the ground’ comment is a stretch, precisely because of the radiation you’re talking about, but maybe someday… Meanwhile, a robust rover that could handle the radiation (and that’s also a challenge for long-term operation) might find some interesting evidence of life if it’s there. Assuming Dr. Lipps is right about organisms conceivably thrust up through the ice here and there, maybe flash-fossilized in an ice ridge for study.

Administrator February 24, 2007 at 17:57

Darnell, I have no idea what we might find under that ice either. Be aware, though, that we don’t have a good idea of the depth of the ice; some estimates are much thinner than the 20-miles you’re suggesting. Heat from tidal friction offers one conceivable energy source.

pinlighter February 24, 2007 at 18:34

What possible source of energy is there under this ice?

There’s no light, so no photosynthesis

Any chemical reaction that might be exploited will run down when its substrate is exausted.

Terran deep ocean biomes are not an analog – they depend on oxygen to oxydise the chemicals erupted.

No vulcanism, no mantle convection.

????????????

Administrator February 24, 2007 at 19:52

Here’s one take on an energy source for Europa, in Borucki et al., “A new energy source for organic synthesis in Europa’s surface ice.” It’s in the Journal of Geophysical Research:

http://www.agu.org/pubs/crossref/2002/2002JE001841.shtml

Which is not to say that it’s correct but that there are various ideas in play, including your own, that there may be no energy source at all.

btester February 28, 2007 at 23:39

friction from jovian gravitational pull?

Administrator March 1, 2007 at 8:52

Yes, Jupiter’s gravity and tidal effects from the other Galilean moons are frequently mentioned in the energy discussion for Europa. It will take a close look by future spacecraft to determine which, if any, of these energy sources actually play a role here. It is always possible that the place is as dead as our Moon, but let’s hope for a more interesting outcome.

ljk March 12, 2007 at 10:16

New directions in the search for life in our solar system

For a decade the mantra guiding the exploration of Mars has been
“follow the water”. Jeff Foust reports on how the focus on the
search for life on Mars may be changing, as well as the continued
interest in Jupiter’s moon Europa.

http://www.thespacereview.com/article/827/1

ljk January 2, 2008 at 14:27

Hydrothermal Systems in Small Ocean Planets

Steve Vance, Jelte Harnmeijer, Jun Kimura, Hauke Hussmann, Brian
deMartin, and J. Michael Brown

Astrobiology, Vol. 7, No. 6: 987-1005.

http://www.liebertonline.com/doi/abs/10.1089/ast.2007.0075

————————————————————————
Energy, Chemical Disequilibrium, and Geological Constraints on Europa

Kevin P. Hand, Robert W. Carlson, and Christopher F. Chyba
Astrobiology, Vol. 7, No. 6: 1006-1022.

http://www.liebertonline.com/doi/abs/10.1089/ast.2007.0156

Adam January 2, 2008 at 16:35

Hey look at this quote from the Hand, Carlson & Chyba paper…

If delivery periods are comparable to the observed surface age (30–70 Myr), then Europa’s ocean could reach O2 concentrations comparable to those found in terrestrial surface waters, even if 109 moles yr1 of hydrothermally delivered reductants consume most of the oxidant flux. Such an ocean would be energetically hospitable for terrestrial marine macrofauna.

…my estimation of the odds for life on Europa have gone up multi-fold with the discovery of even more energy sources. Especially if Chris Chyba is involved – he’s not one to jump to conclusions.

Macrofauna! Perhaps there are tidal pockets in the ice-shell which go up close to the surface as the ice-shell flexes in different directions over the course of an orbit. If we can spot one that might be the place to try to penetrate below the ice.

Administrator January 2, 2008 at 21:56

Adam, which paper is this? Oxygen concentrations comparable to terrestrial surface waters — that’s quite a prospect!

Adam January 3, 2008 at 8:23

Hi Paul

It’s from the paper Larry posted just above my post…

Energy, Chemical Disequilibrium, and Geological Constraints on Europa

Kevin P. Hand, Robert W. Carlson, and Christopher F. Chyba
Astrobiology, Vol. 7, No. 6: 1006-1022.

http://www.liebertonline.com/doi/abs/10.1089/ast.2007.0156

…so there you go :-)

Administrator January 3, 2008 at 9:11

Hadn’t yet gotten that far in my reading, Adam. What a quote: “Such an ocean would be energetically hospitable for terrestrial marine macrofauna.” Clearly we’ll have to look at Europa again soon in this context.

Adam January 4, 2008 at 2:25

Hi Paul

The quote is straight from the abstract and it nearly knocked me over in surprise. All sorts of images – straight from Greg Benford’s depiction of the aliens under the ice of “Pocks” – sprang into my mind. Even if Europa doesn’t have indigenous life could we seed it? Could we colonise it? Possibilities abound – imagine melting a bubble via nuclear power that brings us closer to the surface, thus letting in sunlight and keeping out the rads.

johnF January 4, 2008 at 9:32

Chris chyba has a long standing interest in europa and its possibilities for life; here are a couple of earlier papers by him on the subject: http://www.liebertonline.com/doi/abs/10.1089/153110703322736123?journalCode=ast
and
http://www.pnas.org/cgi/content/full/98/3/801, sorry these arn’t proper links I’m not sure how to do those here!
I think if there is a liquid water ocean and humans go there, or even send machines there it will end up being colonised by earth life.

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