Europa Capable of Supporting Life, Scientist Says
Written by Nancy Atkinson
Europa. Credit: NASA
The global ocean on Jupiter’s moon Europa contains about twice the liquid water of all the Earth’s oceans combined. New research by Richard Greenberg of the University of Arizona suggests that there may be plenty of oxygen available in that ocean to support life, a hundred times more oxygen than previously estimated.
The chances for life there have been uncertain, because Europa’s ocean lies beneath several miles of ice, which separates it from the production of oxygen at the surface by energetic charged particles (similar to cosmic rays). Without oxygen, life could conceivably exist at hot springs in the ocean floor using exotic metabolic chemistries, based on sulfur or the production of methane. However, it is not certain whether the ocean floor actually would provide the conditions for such life.
Therefore a key question has been whether enough oxygen reaches the ocean to support the oxygen-based metabolic process that is most familiar to us. An answer comes from considering the young age of
Europa’s surface. Its geology and the paucity of impact craters suggests that the top of the ice is continually reformed such that the current surface is only about 50 million years old, roughly 1% of the
age of the solar system.
Greenberg has considered three generic resurfacing processes: gradually laying fresh material on the surface; opening cracks which fill with fresh ice from below; and disrupting patches of surface in place and replacing them with fresh material. Using estimates for the production of oxidizers at the surface, he finds that the delivery rate into the ocean is so fast that the oxygen concentration could exceed that of the Earth’s oceans in only a few million years.
Greenberg says that the concentrations of oxygen would be great enough to support not only microorganisms, but also “macrofauna”, that is, more complex animal-like organisms which have greater oxygen demands. The continual supply of oxygen could support roughly 3 billion kilograms of macrofauna, assuming similar oxygen demands to terrestrial fish.
The good news for the question of the origin of life is that there would be a delay of a couple of billion years before the first surface oxygen reached the ocean. Without that delay, the first pre-biotic chemistry and the first primitive organic structures would be disrupted by oxidation. Oxidation is a hazard unless organisms have evolved protection from its damaging effects. A similar delay in the
production of oxygen on Earth was probably essential for allowing life to get started here.
Richard Greenberg is the author of the recent book “Unmasking Europa: The Search for Life on Jupiter’s Ocean Moon.” He presented his findings at the 41st meeting of the American Astronomical Society’s Division for Planetary Sciences.
Source: AAS DPS
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October 8th, 2009 at 12:50 pm
Good to hear, but does all life in the entire universe really need oxygen…
October 8th, 2009 at 1:54 pm
I have to ask the question about energy flow through. I am not an expert on this topic, but life requires more than water and oxygen. You must have energy flow through at a sufficient rate to keep biological systems going.
LC
October 8th, 2009 at 2:26 pm
Lawrence, the common notion is that most of the energy for life would come from the same source the energy needed to keep the ocean liquid comes from, i.e., tidal dissipation and radioactive decay. That heat wouldn't be directly used, but would generate chemical species that can be used for chemiossynthesis, much like happens on Earth's deep oceanic vents.
There are some exotic ideas involving surface organisms along the cracks, using solar power, but they are pretty exotic indeed.
It would probably make a rather poor biosphere, but I think it's very possible.
October 8th, 2009 at 2:43 pm
Heh! Until the last two paragraphs I was thinking "but this is terrible!" But with a delay until oxygenation, wonderful.
Regarding habitability I haven't read much, but the earlier modeling efforts I've seen have been Drake equation type estimates. However, Mendez have developed quite a nice quantitative method, where Mars and Europa places just behind Earth in global habitability, based on planetary models. Due to its large ocean Europa compares well with Earth in potential biomass. See the nice diagram!
The large surprise, at least for me, is that Enceladus is the solar system winner in potential habitability. Unfortunately it's an inaccessible habitat:
"Enceladus has the smallest volume but the highest habitat-planet size ratio followed by Europa. Surprisingly, it also has the highest mean habitability H, in the solar system, although too deep for direct exploration. Mars and Europa are the best compromise between potential for life and accessibility."
I haven't caught up with the solar system part of the research, but the earlier work seems sound. By modeling land plant environmental responses Mendez matches Earth detailed Net Primary Productivity curve (biomass as a proxy for energy flow) over the globe. And that with only two independent factors depending on temperature and relative humidity.
Similar factors are said to describe prokaryote productivity. And they are neatly free from model assumptions of cellular life et cetera, it's probably mostly dependent on observing carbon metabolism (slightly modified by having protein enzymes involved).
So habitability as generally a suitability for life seems better described as a measure of productivity, not probability for life occurring.
October 8th, 2009 at 4:27 pm
Until we send a probe to Europa we'll never know whether life exists or not, but nonetheless, this is exciting news. LC,(or anyone else) what types of challenges would we face in actually landing a robotic probe on the surface? I can imagine they would be immense.
October 8th, 2009 at 7:01 pm
I have an alternative interest in Europa. I have this idea of using acoustical tomography to map out the tracks from cosmic rays frozen in the ice. Effectively there should be 10^6TeV particle physics frozen on that moon. So it would be of interest to me if a probe were landed there with a rover that conducted these measurments.
As for getting under the ice caps, that might be tough. I suppose a nuclear reactor that generates a lot of heat might melt its way through eventually. From there a probe capable of managing what ever environment under there might then conduct a search for life.
The mission profile would be considerable, and costly. There is no atmosphere where parachutes can be used, so it has to retrorocket all the way down. Fortunately the moon is pretty small so the gravity is not much. To be honest I would imagine the landing craft to be the size of the Apollo lunar module. There would then be a rover deployed to study the surface (with my particle physics "sonogram" included I hope) and an nuclear reactor "drill" probe dropped through the ice. Once through some probe would proceed to explore this environment.
I am aware there is some Jovian mission planned set to flyby Europa to detect the thickness of the ice. This will of course have some bearing on the potential presence of life there.
LC
October 9th, 2009 at 1:20 am
William928, there's development in at least US, and surprisingly Sweden, on free roving 'worms' and subs to be able to get to and maneuver underground water bodies.
Of course the best work is the US sub resources, but swedish research interests in miniature worm probes akin to the miniature SMART probe technology may well pay off in terms of ROI. Think of a "multiple probe head" doing the difficult drilling down, and then releasing a swarm of probes. Or you could perhaps go for a smaller drill.
There's some thought going into how to minimize biological contamination too, I believe. Not that it's a big concern of mine, any native organisms will compete well with imports, it's just a free snack for them. In fact, I believe you could make a good argument for culturing probe surfaces with known and genome mapped organisms instead.
On the Jovian mission, I believe they develop a special radar antenna for ice depth mapping. But I'm uncertain if they will be able to see possible thick ices. IIRC Europa is modeled as either thin conductive ice (um, on the order of km ?) or thick convective (at a guess several 100 km), right? Perhaps if you can't see the end of the ice you have the habitability answer right there…
October 9th, 2009 at 9:52 am
I don't know why they are getting excited about the availability of oxygen on Europa because oxygen was highly toxic to early life. It wasn't until long after the origin of life that oxygen was used by most organisms and this was a very lengthy transition. It seems to me that the availability of high concentrations of oxygen would decrease the possibility that life exists there, unless the oxygen comes from life itself. If it comes from solar wind and geological processes, it would likely inhibit the formation of life because oxygen is so reactive.
October 9th, 2009 at 1:25 pm
I'd like to know how that water was created in the first place? Solar system formation remnant? or perhaps through a ongoing/continuing process?
Does Sol, as part of its internal mixing and evolutionary process continually release ionized oxygen and hydrogen? Yes? And perhaps in historical times with volume to create spontaneous coincidental Ice ages throughout the solar system?
October 10th, 2009 at 3:22 am
Kawarthajon you didn't read the article did you? The oxygen took a couple of billion years to build up, providing time for life to arise.
This isn't exactly news though. There was a paper on this idea a couple of years back.