June 20, 2010
Europa May Contain Extraterrestrial Ocean Life
One might find that Jupiter's moon Europa to have extraterrestrial life after fossil-hunting on the icy surface.
"A prospector sent there could possibly find extraterrestrial life within our lifetimes," planetary scientist Richard Greenberg at the University of Arizona's Lunar and Planetary Laboratory in Tucson told Space.com.
A global ocean that may be about 100 miles deep envelops Europa. An icy crust of unknown thickness overlies this ocean, although some estimates say that it is only just a few miles thick.
Scientists have entertained the notion for years that Europa could support extraterrestrial life.
Recent findings have suggested that its ocean could be loaded with oxygen, enough to support millions of tons worth of marine life, similar to the type that exists on Earth.
Scientists have proposed missions to drill through its outer shell, perhaps using heat to melt through ice, in order to explore the ocean.
"With that vision in mind, NASA has a multi-staged plan, first with a Europa orbiter scheduled for 18 years from now, and 10 or 20 years after that, a lander to see what the surface is like, and then maybe a generation later, hopefully we can figure out how to drill all the way down through the ice," Greenberg noted. He recently wrote a book, "Unmasking Europa," which touched upon how one might search for life on the Jovian moon.
However, rather than deploying complex equipment needed to penetrate an uncertain distance into the ice, the remains of marine life on Europa could be right on the outer shell.
Scientists are not suggesting that any life from Europa somehow managed to dig its way up through the ice. Instead, Greenberg said that the constant upheaval Europa undergoes could drag unwitting organisms upward.
The scarcity of craters seen on Europa could mean that the ice shell is no older than 50 million years old. The culprit for this extraordinary activity is the gravitational pull Europa experiences from Jupiter. This causes about 1,000 times stronger forces than what Earth feels from our moon, flexing and heating Europa and constantly stirring its crust.
Ice regularly gets pushed up from below, leading double ridges about 330 feet high to form and cover at least half of Europa's surface. Parts of the surface could also partially melt from below, creating rafts of ice that break loose and tumble around.
This process creates the "chaotic terrain" that makes up about 40 percent of the ice shell, and also sends matter both upward and downward.
"If there are organisms in Europa's ocean, one could well imagine that all over the surface there might be frozen chunks of that stuff," Greenberg said. "People are talking about various kinds of drills and melting down through the ice, and I think we can jump past that and sample the ocean from the surface."
Greenberg said that one of the best places to look for fossils on the moon would be newly formed double ridges.
"The ridges that crisscross others are going to be the most recent ones," he explained. "One could then imagine landers scooping up the ice and analyzing it."
Chaotic terrain would also be another good area to explore, as would an active crack in Europa's crust.
"If we can land right next to an active crack, there's a good chance we could sample some of the most recent ice," Greenberg said. "If we could put a penetrator into it, we could even sample water as it comes up."
Planetary geologist Brad Dalton of NASA's Jet Propulsion Laboratory said that if any microbes did manage to make their way to Europa's surface, the constant stream of radiation from Jupiter would likely break their proteins down over time.
He also said that Dalton's experiments have suggested orbiters could investigate the infrared signature of Europa's icy crust to look for tattered remnants of life. Landers could conduct even more detailed analyses.
Also "there's always the possibility that we could find structures "” something analogous to skeletal remains," Greenberg told Space.com.
Dalton said that if landers dug "even a meter or so down might also be able to find viable organisms, if there are any there."
If there is life in Europa's ocean then it still remains uncertain whether it would indeed get lofted up via geological processes to its surface. However, if no life is seen on the moon's surface then that does not mean there is no life in Europa's ocean.
"My point is only why wait to look for life at the hardest place on Europa to get to?" Greenberg said. "Why not go to the easy place first?"
Image Caption: Europa's trailing hemisphere, as seen by the Galileo spacecraft. The prominent crater in the lower right is Pwyll. Darker regions are areas where Europa's primarily water ice surface has a higher mineral content. Credit: NASA
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