Europa in the High Arctic

by Paul Gilster on December 23, 2010

Yesterday’s post discussed interesting terrain on remote moons, Rhea and Europa among them. But while we can piece together much useful information about a moon’s surface and its history from orbit, some of the most provocative places in the Solar System may well require investigation on the ground. In the case of Europa, that means robotic equipment, but the issue is stark, as Damhnait Gleeson (JPL) recently told Wired.com. “What we can see from orbit is such a simple picture compared to the surface,” Gleeson said in a story on Europa analogues on Earth. “From orbit it’s just ice and sulfur. We really have to go deeper to understand the system.”

That’s just what Gleeson and colleagues have been doing with data and samples gathered at the Borup Fjord Pass on Ellesmere Island, a remote and all but inaccessible place in the Canadian High Arctic. Gleeson, who as a graduate student worked under Europa specialist Bob Pappalardo (JPL), spent time at the pass in 2006, taking samples of the unique yellow stains left by sulfur-rich springs on the surface of the ice. The team’s work proceeded in a starkly beautiful landscape that scientists believe may hold clues about what happens on Europa, with implications for finding life on the moon.

Image: At Borup Fjord Pass, sulfur-rich stains blanket the white, snowy glacier. Credit: Stephen Grasby.

You may have run into this work when The Planetary Society took an interest and provided partial funding for the 2006 study. The reasons for its interest are apparent when you consider that the amount of sulfur at Borup Fjord Pass is what Pappalardo calls ‘an unusual chemical combination.’ The glacial spring at Borup Fjord deposits sulfur, gypsum and calcite across glacial ice. We’d expect pure sulfur to react with oxygen to form gypsum, but the team was able to show that the sulfur was being replenished by microorganisms. Usefully, the sulfur produced by the microbes shows a complicated structure that is not apparent in control samples.

Cut to Europa, where sulfur-rich materials are found concentrated along cracks and ridges on the surface. Do compounds in the ice contain organic material from the ocean below? It’s a huge question, as Gleeson told Astrobiology Magazine in this article last March:

“Europa’s liquid water layer contains twice the volume of all the Earth’s oceans combined, an enormous potentially habitable environment, not billions of years in the past but at the present day. The composition of the ocean directly controls our view of the habitability of the environment, our understanding of whether microbial life could survive there, and if so, what metabolic pathways or geochemical gradients it could utilize to gain energy.”

The Borup Fjord Pass studies, then, are all about comparing Europa’s surface compounds with the sulfur and glacial ice combination found on Ellesmere Island, and indeed, the spectral properties of the glacial ice in the Arctic proved similar to what we see on Europa’s surface. All of this makes Ellesmere Island a potential testbed for instrumentation that will one day travel to Europa. Chemicals circulating between the ocean and the ice layer could produce the energy life needs to exist. The Europan surface is doubtless too saturated with radiation for life to exist there, but a robotic lander might uncover traces of organic material migrating from below.

Image: A Galileo image of the Europan surface. Sulfur-rich materials here may help us understand the composition of the astrobiologically interesting ocean beneath the ice. Credit: NASA/JPL/University of Arizona/University of Colorado.

But absent a lander, this work should prove useful for future orbital observation of Europa as well. The Galileo spacecraft’s spectrometers were able to obtain data in the near-infrared but not enough to resolve the mixture of compounds that left this particular spectral signature. Gleeson’s work continues to investigate the Ellesmere sulfur deposits with spectral studies in the near-infrared and space observations of the site from the Hyperion spectrometer aboard the Earth Observing 1 spacecraft. The next time we get to Europa, we’ll have a better read on what to look for.

The most recent work on Arctic analogues to Europa is Gleeson et al., “Characterization of a sulfur-rich Arctic spring site and field analog to Europa using hyperspectral data,” Remote Sensing of Environment Vol. 114, Issue 6 (15 June 2010), pp. 1297-1311 (abstract).

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{ 15 comments }

James M Essig December 23, 2010 at 12:24

I would like to wish Paul Gilster and Marc Millis, as well as all of those affiliated with Tau Zero and Centauri Dreams and Project Icarus as well as the many commentors who post here at Centauri Dreams a wonderful and joy filled Holidays and a Great and Happy New Year.

Let us work for bold things in the new year, and dream about what dream may come.

Ad Astra Incrementis for all of humanity.

Jim

Adam December 23, 2010 at 20:13

I second James’ motion! Merry Xmas to Paul, Marc, CD & the TZF!

Adam December 23, 2010 at 20:21

I was just thinking about Europa today, in the context of the alien invasion film “Monsters”, which was done on a very low budget, but with the interesting premise that the ‘invasion’ was an accidental release of Europan life-forms via a sample return mission. I think that’s a distinct possibility, oxygen-breathing life on Europa, though I doubt the Europas will be giant luminescent octopoids. The biosphere can probably only sustain some fish-sized organisms. But who knows?

The recent photographs of gliding squid, flying through the air, does make one wonder just what might inherit the Earth after vertebrates are gone. The ‘documentary’ from a few years ago, “The Future is Wild”, posited ‘flish’ replacing birds and various molluscs as new land animals in 200 billennia time, but perhaps the ‘flish’ might need to compete with the flying-squid?

Paul Gilster December 23, 2010 at 21:28

All these good vibes, both here and via emails, are much appreciated, and let me wish all Centauri Dreams readers the best for the holidays. Will 2011 be the year we find interesting things around Centauri B? Or maybe a fully confirmed planet in the habitable zone of some interesting M-dwarf? I’m looking forward to finding out. Thanks to all of you for your participation in the past year, and indeed in all of the six years-plus this site has been operational.

Michael Spencer December 24, 2010 at 8:30

Hi Paul,

“We’d expect pure sulfur to react with oxygen to form gypsum”

Chemistry alert! Gypsum is Ca2SO4+2H2O, I think? I am sure you sourced that comment so I cannot figure out how the chemistry works?

And this: I’ve mentioned to you before how much I appreciate your writing style…I do a column every week of about 1000 words and appreciate your task, maintaing the writing quality, let alone content, day after day…I admit to occasionally stealing a turn of phrase…

Michael Spencer

Paul Gilster December 24, 2010 at 8:46

Michael, Gleeson mentions this in a 2006 JPL news release:

“Finding so much sulfur is the clue that there’s a continuous supply of it being produced, otherwise it would have become gypsum.”

But I think I pulled the reaction with oxygen from the Wired article:

“‘It’s so unusual to find ice and sulfur together on Earth,” Gleeson said. “It’s really not what you’d expect to see.” On Earth, most pure sulfur reacts with oxygen to form the soft mineral gypsum.”

Please correct if this is wrong — I’m no chemist! And thank you for those kind words about my work. Doing a regular column has much in common with regular blogging, as I’ve learned by doing both over the years. Feel free to swipe that occasional turn of phrase ;-)

bigdan201 December 24, 2010 at 14:42

This reminds me of Mars rovers being tested out in the Mojave desert. The Earth is a convenient place to do studies that can apply elsewhere.

Is there any word on how thick the global ice sheet on Europa is? Ideally, a Europa mission would drill through the ice to investigate the ocean directly – so information on ice thickness and also variation in thickness would be useful.

Rob Henry December 25, 2010 at 20:26

Adam brings up the possibility of large complex Europans. This seems an unlikely prospect yet it is a repeated theme in astrobiology. As far as I can make out this idea rests on three points. The first is to postulate either that abiogenesis is an easy process or lithopanspermia is an efficient process. The evidence today at least points to the early solar system being conducive to the interplanetary spread of hardy endolithic bacteria into receptive environments. Due to the gravitational collapse heating, Jupiter radiated so much heat in the early solar system that Europa was apparently warmer than now even if it received less insolation, so it may have been more conducive to life then.
The second is that the evolution of complex multicellular life on Earth was not a fluke, but had environmental triggers. If so the main contenders for this trigger event seem to be the rising levels of free oxygen, and the effects of snowball Earth. We have good reasons to believe that both those conditions apply on Europa.
The third is that there might be a sufficiently high flux of biologically useful energy on Europa. Several current ideas for such a mechanism allow for a thriving bacterial community at best ideas, but there are exceptions. Richard Greenberg calculated that sufficient oxygen could be generated on Europa’s surface, and supplied to life below, to support the equivalent of a three million ton ecosystem of Earthly fish. If not, the other hope may be in that the Laplace resonance Galileans should go through cycles of tidal activity. We might be seeing Europa at a low point, its icy crust normally being so very thin as to allow photosynthesis or rapid recycling chemicals that could be energized by surface radiation. Perhaps, between these cycles, complex life clings on around hydrothermal vents.
Please let me know if I am missing any vital point.

Adam December 25, 2010 at 23:01

Hi Rob Henry
Nice summary. About right too. I first saw a “Voyager I” shot of Europa in c.1979 on TV then in an astronomy book and from that point on I followed the ideas about Europa, from Clarke’s fictional speculations in “2010″ through to the debates throughout the 1990s over the rheology of ice, and Greenberg’s work on the putative ocean’s oxygenation. It’s a fascinating little world and perhaps a sign-post to even more clement worlds. As you note even Earth appears to have had ice-locked oceans several times in geohistory, so it’s not a state incompatible with life-as-we-know-it.

Rob Henry December 26, 2010 at 18:47

Hi Adam
I think it possible that you have interpreted me slightly incorrectly. Bacterial-type life could definitely cling on in many places in our solar system but multicellular eukaryote life is very fussy. Sure, it soon dies if conditions are too hash, but more importantly it is always out competed by bacterial grade life if conditions are too good. Think what happens if you tip fertiliser into a river or providing a pot plant with too much light and moisture. Given this we must explain how complex life ever appeared on Earth. IFF it was due to the oxygen catastrophe or Snowball Earth tipping the balance in favour of complex solutions to life’s problems THEN we can EXPECT complex life to have evolved on Europa. Complex life may die easily, but on Earths polar ice caps and deserts it seems to have clung on way better that fungi, let alone bacteria , archaea or viruses.

David December 27, 2010 at 11:54

let me start by saying that all of the information and discussions on this site are amazing and I am a huge fan. With that being said I would like also to make sure that everyone knows that I am just A fan… So please overlook any ignorance.
The thing that occurs to me in this post is that we are in sore need of instrumentation that would allow for better penetration of surfaces… The problem seems to be that “scanners” like those in the airports (not exactly those but some similar and much more powerful) could be used to actually penetrate the surface. Hyper-focused and directed at thermal vents couldnt some version of this be used to cailibrate the depth of the ice and detect motion? I realize that the life on europa (if there is any) may be microscopic and undetectable in this way, but densities and structures could be viewed and a plethora of information gleened. This reminds me of the starship Enterprise… It could detect life forms on a new planet and calculate how many…this doesn’t seem impossible to me, and probably doable with existing tech… Please correct me if I am totally off.

actually reminds me of the starship Enterprise in its ability to discern what a new planet was made of and calculate how many life forms were on the surface and what they consisted of… Thank you for your patience, and please correct me if this is impossible, but it just seems like a needed step before we can move on to other worlds….we need to know more than the chemical

andy December 27, 2010 at 17:57

Essentially any icy planet located sufficiently far from a star can support an ocean until it cools off sufficiently after its formation for the ocean to completely freeze. Contrast that with Earth-type surface oceans which are confined to a narrow range of distances in their solar systems. It may well be that most biospheres in the universe are found on cold icy worlds rather than Earth-analogues.

David December 31, 2010 at 10:57

Sorry about my earlier post. I’m using my cellphone and thought I had lost some of what I wrote. Maybe I should ask if anyone knows how our probes discern if their is liquid under the ice besides the obvious spouts of water shooting from the surface.

Eniac January 1, 2011 at 13:53

It appears to me that Europa primarily calls for 1) seismic monitoring, and 2) drilling. Drilling, of course, would be preferable, but it is difficult and risky. A handful of small and simple landers with the ability to knock on the ice and listen would go a long way towards knowing the exact composition of the moon and the extent of its interior ocean. Plus, if there where whales, we would hear their songs.

Another interesting option would be a penetrator probe, i.e. a projectile built to withstand a hard landing in the ice that would propel it right through to the interior ocean. I am not sure if that is feasible, we’d probably have to look for a crack in the ice or a soft spot of some sort and hit it just right.

Once we’re there, exploration would be relatively easy and wide-ranging, in the manner of a submarine. The tricky part is maintaining a communications link under water. I understand Earthly submarines use long trailing cables to communicate via long-wave radio, perhaps that would work. Or, use sound, with the above mentioned seismic stations as relays. Hopefully without chasing the whales away….

ljk January 31, 2011 at 4:10

Gibbous Europa

Credit: Galileo Project, JPL, NASA; reprocessed by Ted Stryk

Explanation: Although the phase of this moon might appear familiar, the moon itself might not. In fact, this gibbous phase shows part of Jupiter’s moon Europa. The robot spacecraft Galileo captured this image mosaic during its mission orbiting Jupiter from 1995 – 2003. Visible are plains of bright ice, cracks that run to the horizon, and dark patches that likely contain both ice and dirt. Raised terrain is particularly apparent near the terminator, where it casts shadows. Europa is nearly the same size as Earth’s Moon, but much smoother, showing few highlands or large impact craters. Evidence and images from the Galileo spacecraft, indicated that liquid oceans might exist below the icy surface.

To test speculation that these seas hold life, NASA and ESA have started preliminary development of the Europa Jupiter System Mission, a spacecraft proposed for launch around 2020 that would further explore Jupiter and in particular Europa. If the surface ice is thin enough, a future mission might drop hydrobots to burrow into the oceans and search for life.

http://apod.nasa.gov/apod/ap110130.html

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