New Evidence Found for Europa's Vast Ocean --Increases Potential for Life
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March 05, 2013

New Evidence Found for Europa's Vast Ocean --Increases Potential for Life

 

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Based on new evidence from Jupiter's moon Europa, astronomers hypothesize that chloride salts bubble up from the icy moon's global liquid ocean and reach the frozen surface. Mike Brown, an astronomer at the California Institute of Technology (Caltech). Brown—known as the Pluto killer for discovering a Kuiper-belt object that led to the demotion of Pluto from planetary status—and Kevin Hand from the Jet Propulsion Laboratory (JPL) have found the strongest evidence yet that salty water from the vast liquid ocean beneath Europa's frozen exterior actually makes its way to the surface.

Hand emphasizes that, from an astrobiology standpoint, Europa is considered a premier target in the search for life beyond Earth; a NASA-funded study team led by JPL and the Johns Hopkins University Applied Physics Laboratory have been working with the scientific community to identify options to explore Europa further. "If we've learned anything about life on Earth, it's that where there's liquid water, there's generally life," Hand says. "And of course our ocean is a nice salty ocean. Perhaps Europa's salty ocean is also a wonderful place for life."

"We now have evidence that Europa's ocean is not isolated—that the ocean and the surface talk to each other and exchange chemicals," says Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy at Caltech. "That means that energy might be going into the ocean, which is important in terms of the possibilities for life there. It also means that if you'd like to know what's in the ocean, you can just go to the surface and scrape some off."

The finding, based on some of the first data of its kind since NASA's Galileo mission (1989) to study Jupiter and its moons, suggests that there is a chemical exchange between the ocean and surface, making the ocean a richer chemical environment, and implies that learning more about the ocean could be as simple as analyzing the moon's surface. "The surface ice is providing us a window into that potentially habitable ocean below," says Hand, deputy chief scientist for solar system exploration at JPL.

Since the days of the Galileo mission, when the spacecraft showed that Europa was covered with an icy shell, scientists have debated the composition of Europa's surface. The infrared spectrometer aboard Galileo was not capable of providing the detail needed to definitively identify some of the materials present on the surface. Now, using current technology on ground-based telescopes, Brown and Hand have identified a spectroscopic feature on Europa's surface that indicates the presence of a magnesium sulfate salt, a mineral called epsomite, that could only originate from the ocean below.

"Magnesium should not be on the surface of Europa unless it's coming from the ocean," Brown says. "So that means ocean water gets onto the surface, and stuff on the surface presumably gets into the ocean water."

Europa's ocean is thought to be 100 kilometers deep and covers the entire globe. The moon remains locked in relation to Jupiter, with the same hemisphere always leading and the other trailing in its orbit. The leading hemisphere has a yellowish appearance, while the trailing hemisphere seems to be splattered and streaked with a red material.

The spectroscopic data from that red side has been a cause of scientific debate for 15 years. It is thought that one of Jupiter's largest moons, Io, spews volcanic sulfur from its atmosphere, and Jupiter's strong magnetic field sends some of that sulfur hurtling toward the trailing hemisphere of Europa, where it sticks. It is also clear from Galileo's data that there is something other than pure water ice on the trailing hemisphere's surface. The debate has focused on what that other something is—i.e., what has caused the spectroscopic data to deviate from the signature of pure water ice.

"From Galileo's spectra, people knew something was there besides water. They argued for years over what it might be—sodium sulfate, hydrogen sulfate, sodium hydrogen carbonate, all these things that look more or less similar in this range of the spectrum," says Brown. "But the really difficult thing was that the spectrometer on the Galileo spacecraft was just too coarse."

Brown and Hand decided that the latest spectrometers on ground-based telescopes could improve the data pertaining to Europa, even from a distance of about 400 million miles. Using the Keck II telescope on Mauna Kea—which is outfitted with adaptive optics to adjust for the blurring effect of Earth's atmosphere—and its OH-Suppressing Infrared Integral Field Spectrograph (OSIRIS), they first mapped the distribution of pure water ice versus anything else on the moon. The spectra showed that even Europa's leading hemisphere contains significant amounts of nonwater ice. Then, at low latitudes on the trailing hemisphere—the area with the greatest concentration of the nonwater ice material—they found a tiny dip in the spectrum that had never been detected before.

"We now have the best spectrum of this thing in the world," Brown says. "Nobody knew there was this little dip in the spectrum because no one had the resolution to zoom in on it before.

The two researchers racked their brains to come up with materials that might explain the new spectroscopic feature, and then tested everything from sodium chloride to Drano in Hand's lab at JPL, where he tries to simulate the environments found on various icy worlds. "We tried to think outside the box to consider all sorts of other possibilities, but at the end of the day, the magnesium sulfate persisted," Hand says.

Some scientists had long suspected that magnesium sulfate was on the surface of Europa. But, Brown says, "the interesting twist is that it doesn't look like the magnesium sulfate is coming from the ocean." Since the mineral he and Hand found is only on the trailing side, where the moon is being bombarded with sulfur from Io, they believe that there is a magnesium-bearing mineral everywhere on Europa that produces magnesium sulfate in combination with sulfur. The pervasive magnesium-bearing mineral might also be what makes up the nonwater ice detected on the leading hemisphere's surface.

Brown and Hand believe that this mystery magnesium-bearing mineral is magnesium chloride. But magnesium is not the only unexpected element on the surface of Europa. Fifteen years ago, Brown showed that Europa is surrounded by an atmosphere of atomic sodium and potassium, presumably originating from the surface. The researchers reason that the sodium and potassium chlorides are actually the dominant salts on the surface of Europa, but that they are not detectable because they have no clear spectral features.

The scientists combined this information with the fact that Europa's ocean can only be one of two types—either sulfate-rich or chlorine-rich. Having ruled out the sulfate-rich version since magnesium sulfate was found only on the trailing side, Brown and Hand hypothesize that the ocean is chlorine-rich and that the sodium and potassium must be present as chlorides.

Therefore, Brown says, they believe the composition of Europa's sea closely resembles the salty ocean of Earth. "If you could go swim down in the ocean of Europa and taste it, it would just taste like normal old salt," he says.

The work is described in a paper that has been accepted for publication in the Astronomical Journal.

The Daily Galaxy via NASA/JPL-Caltech

Comments

We definitely need to send a probe to Europa.

Incredibly fascinating these times we live in and definitely have to send more probes with ever more precise instruments - can't wait.

Even if it does not harbor life We can send a probe with a organism which could live and reproduce in such environment.
Then after some years we would have a place where could use for resupply or/and set a bases, and develop further an eco system on Europa.

Europa might be our backyard kindergarden to study further about Teraforming and Eco System evolution.

"We definitely need to send a probe to Europa."

Well, we are out of luck : NASA is obsessed with Mars :
http://www.scientificamerican.com/article.cfm?id=has-nasa-become-mars-obsessed

and it has earmarked $5B for Mars (Curiosity, MAVEN, Insight and Curiostiy 2) but zilch for Europa or Titan.
No money is left for any such probe for the foreseeable future.
All while Mars looks less and less habitable with each mission.
If we are lucky we will get 2 fly-bys in 2032 during ESA mission to Ganymede.

Just think what we could achieve with the money that is spent on weapons of war and money lost through corruption, A giant base on the moon from which to explore the solar system. Only doing that kind of thing will we truly become a space faring Species

Mars has many points plus before Europa even if it doesn`t have life . It is a planet (still, we don`t know what it will be next year when some idiot will change again the classification). It is very close to us compared to Europa. It has a good potential for solar powerups (on Europe the Sun is barely visible). It has water too on it (even it`s solid). The level of radiation is not so high as on Europe where nobody would resist more than days (yeah, Jupiter has that effect on his close moons). It is easy to re-supply with stuff in case of human base on it not only for distance, but for gravity and atmosphere problem, it will be a challenge to land a ship near Jupiter (and Europe is too close) anytime soon. Also the temperatures are lower on Europa, even if underwater it will be nicer, but we don`t have a cutingedge technology for underwater even here on Earth, it`s something completly new for a space agency.

@Gaugain,

You seem to be seeing this from a manned spaceflight point of view. If that is the case, then the extra attention to Mars should come from manned spaceflight funds. The space SCIENCE funds should be spent on scientific targets and, as things stands, a program that spends $5B on a single target and much much less on all the rest is highly unscientific.
The scientific unmanned spaceflight program, with very little funds has achieved a lot. In contrast, the manned one, with billions of funds (see the $100 B space station), after 40 years is still stuck in LEO.
It is ridiculous requiring the small scientific unmanned program to subsidize the white elephant manned one. They can pay for all the extra Mars missions they want in preparation of the ever postponed Mars landing, all I ask is that limited scientific funds are spent scientifically and equitably. This doesn't mean no Mars missions, I love Curiosity.
It means that instead of having four of them, axe at least a couple and make room for other solar system targets.
Besides, as long as the manned Mars mission costs $100 B or more, there little chance of that happening.
And Tito's mission, if it happens at all, will fail to inspire anyone for the same reason that everyone remembers Neil Armstrong and none who flew on Apollo 8.

Tito's mission to Mars is just like the Mars-One project. Just isn't going to happen anytime soon. Just too much money and no one has the amount needed. Mars-One is pulling in less than $2,000 per month from the sales of t-shirts and coffee cups. No money, no plan!!


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