A Possible Subsurface Lake on Europa

by Paul Gilster on November 17, 2011

An area of disrupted terrain called Thera Macula on Jupiter’s moon Europa may be evidence for a body of liquid water with the volume of North America’s Great Lakes encased within the ice. The notion comes from analysis of floating ice shelves that seem to be collapsing. That an ocean exists beneath the ice on Europa should surprise no one, but what is significant about the recent findings is that they suggest a way to exchange nutrients and energy between the surface and the ocean beneath. Such a mechanism changes the nature of the speculation about whether Europa’s ice is thick or thin. The case for astrobiology always seemed stronger if the ice were thin, but it seems that ways to exchange material with the surface may exist in either scenario.

At least that’s what this intriguing finding suggests. Britney Schmidt (University of Texas at Austin) is lead author on the paper that appears online in Nature:

“One opinion in the scientific community has been, ‘If the ice shell is thick, that’s bad for biology’ — that it might mean the surface isn’t communicating with the underlying ocean. Now we see evidence that it’s a thick ice shell that can mix vigorously, and new evidence for giant shallow lakes. That could make Europa and its ocean more habitable.”

When you work with Europa, you’re relying on images taken by the Galileo spacecraft, focusing in this case on two bumpy features in the disrupted topography that scientists call chaos terrain. The area known as Thera Macula shows evidence of active resurfacing of ice over a large body of water. Evidence that such terrain can still be forming is good news for those hopeful for life beneath the surface. The speculation is that many such lakes may exist throughout shallow regions of Europa’s shell, many of them covered with similar collapsing ice shelves.

Image: Thera Macula (false color) is a region of likely active chaos production above a large liquid water lake in the icy shell of Europa. Color indicates topographic heights relative to background terrain. Purples and reds indicate the highest terrain. Credit: Paul Schenk/NASA.

The researchers worked with Galileo data and applied processes observed here on Earth in areas where ice shelves are in motion and volcanoes are found beneath overlying glaciers. Their work indicates that chaos terrains “… form above liquid water lenses perched within the ice shell as shallow as 3 kilometres. Our results suggest that ice–water interactions and freeze-out give rise to the diverse morphologies and topography of chaos terrains.” All of this means that nutrients and energy may be available in the deep ocean, but we won’t know for sure until we can develop a mission that is designed to probe beneath the ice. The same kind of radar instruments that study Earth features within ice can be adapted for such a spacecraft.

The paper is Schmidt et al., “Active formation of ‘chaos terrain’ over shallow subsurface water on Europa,” published online in Nature 16 November 2011 (abstract).

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{ 23 comments }

Istvan November 17, 2011 at 12:49

An obvious question, hopefully addressed in the Nature article, is the duration of such features, so that they can be targeted specifically by future probes. The Galileo data is approaching a decade old now, and without better propulsion systems, probe cruise time to Jupiter is typically another five years. Add a design, development, and assembly period of five to ten more years under NASA’s bureaucracy, and it will take us a while to get fresh instruments onsite to give us a better look at Thera Macula or a similar feature on Europa. I’m optimistic, however, as my impression is that except for on highly dynamic Io, most topographic features on outer system bodies have rather long lifetimes.

Tarmen November 17, 2011 at 17:10

Makes me wonder…
The closer we look, the more exceptional geologic features we will discover. Even until some day in the 22nd or 23rd century we will guide robot spelunkers down into endless ravines and caverns, tunnels and tubes twisted and flooded and re-shaped over a billion years of geologic activity. Perhaps even there are some mats of bacteria and fungi . Perhaps luminous or poisonous. Or crawling things, sniffy down toward the sweet liquids or the carbons. Perhaps our smart robots will have to explore down inside Europa in an autonomous mode, leaving us behind. Will they return to the surface with some wondrous discoveries??

Enzo November 17, 2011 at 17:48

@Istvan

No reason to be optimistic regarding a mission to Europa. At the moment there’s no money for it.
There are some studies to reduce costs :
http://futureplanets.blogspot.com/2011/10/europa-new-options.html

But I wouldn’t hold my breath since 3 missions have been proposed but none went ahead.

Some Europa observations might come from an ESA Ganymede orbiter if it is approved:
http://futureplanets.blogspot.com/2011/11/juice-jupiter-ganymede-orbiter-revised.html
The good thing with ESA is that once a mission has been approved, it is unlikely to get cancelled (unlike for example, SIM or some near misses like Cassini and Dawn) .

Enzo November 17, 2011 at 17:59

I understand how warm hot water, coming from a volcano below, could punch a hole in the ice crust.
However, I don’t understand why, once the volcanic activity has subsided, the ice would start reforming from the bottom (as well as the top), leaving a bubble of water in the middle as I’ve seen in pictures like this :
http://www.spaceref.com/news/viewpr.html?pid=35254

Any ideas ?

Bob November 17, 2011 at 18:27

Endless committees, competing groups, 10- to 15 years to get a probe designed and built, budget cycles, launch delays, minimum 5 years to get there and we are looking at least 20 years from now. How depressing…

Or, we could spend the next decades designing and deploying a more general probe building and launching system, based in space, such that a team of grad students could specify a mission, design a probe from generic subsystems, send the specifications to some assembly system in space which builds and launches it to carry out that specific mission. Then hundreds of missions could be conducted. More like getting time on a telescope.

andy November 17, 2011 at 19:45

Interesting, though the thick ice shell proposed in this model will make it rather harder to reach the ocean proper.

Enzo November 17, 2011 at 20:17

The Planetary Society has a posting that answers my question above about water bubbles in ice :
http://www.planetary.org/blog/article/00003266/

jkittle November 17, 2011 at 23:50

Right on Bob!
we need a generalized probe platform with communications and guidance, propulsion, then we can get a lower cost of mission. We can gaindesign and manufacture experience and upgrade chassis design very 5 to 10 years, while building upon an experience operations team in each mission.
Ditto launchers
ditto manned capsules
ditto launching a a series of earth orbiting satellites to enhance deepspace communications
No more 5 billion dollar plus mission unless they are MANNED
four smaller but highly capable IR telescopes are much less risky than one big bloated project

bigdan201 November 18, 2011 at 3:39

I’m fairly confident that there is biology in the subsurface oceans of Europa. This finding is especially encouraging. But what we’ll find there is pure speculation. I wonder what complexity of life can be supported there by the available energy. Will it be mostly plankton/fungi? or will there be larger invertebrae? There probably wouldn’t be enough energy for anything more complex, such as sharks. Of course exobiology is very open-ended, but I imagine that convergence will still play a role.

Ole Burde November 18, 2011 at 8:27

It would be nice if more funding was avaiable , but it isn’t .
Launching a specific mission to Europa must in many ways be similar to the present missions to Mars . If we made more of the more-or-less same kind of investment in spaceteknology , it would be taken away from other , much more neglected areas of development . One good eksample is the recycling teknologies necesary for making a habitat almost independent for longer periods of time . Another would be if no sucsessor to the Kepler mission gets enough funding to identify or rule out signs of life on the candidate planets that kepler will probably identify.
Time will come for investigating Europas oceans , especially if this can be done in a way that international partners pays most of the cost.

djlactin November 18, 2011 at 8:58

Higher around the edges; lower in the centre. Might this instead be the ‘crater’ left by an impact? (Even this interpretation would allow communication between the surface and the underlying water; just by a different means.)

Alex Tolley November 18, 2011 at 11:03

“‘If the ice shell is thick, that’s bad for biology’ — that it might mean the surface isn’t communicating with the underlying ocean. ”

That may be one branch of opinion, but it is somewhat at odds with bacterial life that exists near ocean vents and in the lithosphere itself. I don’t see this feature as having significance unless the issue is some sort of panspermia – e.g. life being acquired elsewhere, perhaps from early Mars. Even then, all we want is a permeable surface ~ 3-4 bya.

@bigdan201: “I’m fairly confident that there is biology in the subsurface oceans of Europa. ” Based on what evidence?

bigdan201 November 18, 2011 at 21:14

@bigdan201: “I’m fairly confident that there is biology in the subsurface oceans of Europa. ” Based on what evidence?

It is pure conjecture, based on the ubiquity of life on earth. If life exists here in almost every conceivable environment, then it follows that it should be able to develop elsewhere. Of course we don’t know much at all about biogenesis, which is a huge variable. However, we do believe that life began in the ocean, so that is one reason to expect exobiology on Europa. My statement was an educated guess more than anything else.

forrest noble November 19, 2011 at 0:36

I consider these large lakes near the surface as very good news. There has been speculation that a Europa ocean toward the lunar core could be too saline, something like the dead sea or worse. Large lakes near the surface are more likely to be closer to fresh water because of the continuous cycle of freezing and thawing, maybe something like icebergs thawing.

In time if we do not find life in any of these underground lakes or ocean, they might become great future food depots for seeding life for the purpose of future food production for solar system travelers, or possibly asteroid or Jupiter moon miners :)

Bob November 19, 2011 at 17:23

“However, we do believe that life began in the ocean, so that is one reason to expect exobiology on Europa. ”

This is an article of faith based on the conservative old dogma that life on earth must have begun on earth. Really the only evidence is that life is here which says nothing about how or where it started. There is growing evidence and theory that supports the concept that microbial life came from elsewhere and seeded earth. At some point that should be the default position.

I would assume that any life discovered off earth would better support the position stated above over the idea that life independently arose however I assume that the latter view will likely be the default position of most scientists unless or until we find enough samples to make that concept seem unnecessary.

bigdan201 November 20, 2011 at 1:32

True, which is why I chose the word “believe”. If life on earth originated elsewhere, that would make it even more likely that there is life in the Europa ocean.

Until we get more hard evidence, we can only speculate. However, the chirality of alien specimens will shed a great deal of light on these matters. The same chirality would support earth being seeded, differing chirality would suggest multiple biogeneses.

Tarmen November 20, 2011 at 14:50

Regarding the panspermia origination idea…
Given that the galaxy is about 7-8 billion years older than our Solar system at just 4 billion or so, I should expect that life should have arisen in many places during those 7-8 billion years before our Sun ignited. And life always tries to preserve itself and reproduce itself. So, it seems likely that the Milky Way some 4 billion years ago was already littered with the ‘life preservers’ of ages past . Maybe pods , or freeze dried fragments of information, or dormant bacteria. Just faint hopes, like coconuts bobbing on the ocean. And/Or perhaps more intelligent Johny Appleseed aliens have purposely dispersed starter seed in every direction before the was an Earth. Maybe various ancient rivals tried to out do each other in ‘taming’ the wilderness.
None of those prehistoric likelihoods would rule out home grown evolution alongside, or replacing one or the other (or others).
A lot of stories were written before there was an Earth .

Bob November 21, 2011 at 13:23

Tarmen, as you know what you wrote is basically the tenants of the Hoyle, Wickramasinghe theory which postulates that genetic material was present when the solar system formed and was introduced into the comets where it exponentially multiplied and eventually seeded earth as well as flinging more genetic material further out into interstellar space.

Wickramasinghe has bacteria data from about 41km up taken with high altitude balloons under highly controlled sterile conditions. The samples were able to replicate and are not the usual types of bacteria expected from earth contamination. Skeptics blow off the data with the usual claim that they must be bacteria lifted up from volcanic action but their own models and the timing of the experiment suggest otherwise.

ljk January 5, 2012 at 10:50

Russia’s Europa lander concept from 2009:

http://futureplanets.blogspot.com/2009/04/russian-europa-lander-concept.html

Check out the presentation papers and posters, most of which are online here:

http://arc.iki.rssi.ru/conf/2009elw/presentations/

ljk March 3, 2012 at 14:26

Europa’s Acidic Oceans May Prohibit Life

by Tammy Plotner on March 2, 2012

The more we explore our solar system, the more we find things in common. Jupiter’s frigid moon – Europa – is about the size of our satellite and – like Earth – home to some very hostile environments.

Underneath what is surmised to be an icy crust a few miles deep, Europa may possess an acidic ocean that could extend down as much as 100 miles (160 km) below the surface.

We know from exploring our home planet that life happens under some very extreme conditions here… But what about Europa? What are the chances that life could exist there, too?

Full article here:

http://www.universetoday.com/93939/europas-acid-oceans-may-prohibit-life/#

ljk March 29, 2012 at 15:42

How deep must life hide to be safe on Europa?

March 29, 2012

By Nola Taylor Redd

Jupiter’s icy moon is subject to constant and significant blasts of radiation. A new experiment attempts to determine how deep life must lay beneath the crust in order to survive. This will be important for future missions looking for life on Europa.

Full article here:

http://www.physorg.com/news/2012-03-deep-life-safe-europa.html

ljk September 28, 2012 at 0:38

Liquid Water Near Europa’s Surface a Rarity

by Staff Writers

Madrid, Spain (SPX) Sep 28, 2012

Europa, the enigmatic moon of Jupiter, is believed to be home to a subsurface ocean of liquid water. However, future missions to explore Europa’s ocean may need to dig deep.

Research suggests that water does not stay in a liquid state near Europa’s surface for longer than a few tens of thousands of years – the blink of an eye in geological terms.

Klara Kalousova will present this work at the European Planetary Science Congress in Madrid on Tuesday 25 September 2012.

Full article here:

http://www.spacedaily.com/reports/Liquid_Water_Near_Europas_Surface_a_Rarity_999.html

ljk November 5, 2012 at 17:48

Crybots Could Drill into Icy Moons with Remote Fiber-Optic Lawser Power

Wired – By Michael Ray Taylor, April 19, 2012

Future extraterrestrial rovers may be powered remotely by high-energy laser beams shot through miles of thin fiber-optic cables. This new technology could allow robotic probes to penetrate thick layers of ice to explore Antarctic lakes or the subterranean oceans on icy moons like Europa or Enceladus, and even power a new kind of rocket into space.

“Our modest goal over the next three years is to use a 5,000-watt laser to send a cryobot through up to 250 meters of ice,” inventor and explorer Bill Stone, who presented the new concept today at NASA’s Astrobiology Science Conference in Atlanta, told Wired. “All the data show there are no show-stoppers for doing that. But from my standpoint, this is child’s play compared to what we could do.”

The problem for scientists hoping to study the ocean of liquid water believed to lie beneath Europa’s icy crust has always been the amount of energy required to melt through miles of ice. Solar power won’t work below the surface, and batteries won’t last long enough. And while a small nuclear reactor might have enough power, the footprint would be too large for a device NASA might realistically expect to drill miles down. A nuclear device couldn’t be tested in Antarctica either, because of international treaty restrictions.

Full article here:

http://www.wired.com/wiredscience/2012/04/bill-stone-laser-powered-europa-rover/

To quote:

However well it works, no cryobot is likely to travel to Eruopa anytime soon. “We just don’t know what the surface of the moon looks like at a lander-sized scale, or whether there is a place flat enough to land,” Robert Pappalardo, a senior research scientist at JPL and head of NASA’s Europa study group, said. Pappalardo said a recent review board expressed “very serious concerns” over authorizing any lander mission to the moon until a new orbiter or fly-by mission can photograph the surface in higher resolution than currently exists.

“We have a few images at 6 meters per pixel for Europa, and that’s not enough to tell,” Pappalardo said. “The one 4-meter-per-pixel image we have of Enceladus looks like a very scary boulder field.”

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