(CN) — The ice shell of the Jovian moon Europa may cover a dynamic system full of pockets of water that make it a prime candidate for extraterrestrial life in our solar system, according to a paper published Tuesday in the journal Nature Communications.
Europa, a moon similar in size to Earth’s moon, features a surface consisting mostly of ice crisscrossed by fractures. The shell likely covers an ocean with more water than all of Earth’s oceans combined, according to NASA. Scientists believe the ice shell is 10 to 15 miles thick, above an ocean 40-100 miles deep. The deepest point on Earth, Challenger Deep, is not quite 7 miles.
The findings were made by three Stanford University researchers after similarities between Europa and the Greenland ice sheet became apparent one day in a research group meeting, during a presentation by planetary scientist Gregor Steinbrügge on scientific questions surrounding Europa.
Riley Culberg, a doctoral candidate in electrical engineering who researches the effects of climate change on the Greenland ice sheet, noticed the double ridges on Europa appeared remarkably similar to those on Greenland's ice sheet.
“I looked at that picture and was like, ‘Whoa! I saw something like that literally earlier today in my own data from Greenland that looks almost identical to these cross sections that he’s seeing,’” Culberg said.
And when the trio of researchers — Culberg, Steinbrügge and Dustin Schroeder — dug into it, they found m-shaped crests called the double ridge in Greenland could be a smaller version of the features on Europa.
The double ridges on Europa appear as dramatic gashes across the moon’s icy surface, with crests reaching nearly 1,000 feet, separated by valleys about a half-mile wide.
Since the 1990s when the Galileo spacecraft passed by, scientists have known about the features on Europa but did not know how they were formed. But Greenland reveals a possible scenario.
The double ice ridge in northwest Greenland was created when the ice fractured around pressurized water refreezing inside the ice sheet, the researchers found through analyses of surface elevation data and ice-penetrating radar collected by NASA’s Operation IceBridge.
“We think this same kind of mechanism could have operated on Europa,” Culberg said.
“What was forming these features in Greenland were actually pockets of water that were being frozen and fracturing into the surface, in a series of freezing and fracture and refreezing and fracturing again, shoved up these double-ridge shapes,” said Schroeder, an associate professor of geophysics at Stanford who supervised the research.
To sustain those pools of water beneath the icy surface of Europa, some sort of cycling needs to be occurring, Culberg said.
“If we had a bunch of shallow water, well, that water had to come from somewhere,” Culberg said. “One of the places it might have come from is water from the ocean that is getting sort of forced up through fractures into the ice shell, or from kind of like convection of the ice inside of the ice shell. The idea of having shallow water kind of implies we have a lot of transport going on in the ice shell, which is probably good at moving around the chemistry that you need for life.”
When it comes to life on Europa, scientists are not even suggesting complex marine life inside the ocean. It would likely be far simpler.
“It’s more like, are the right building blocks there for microbial, single-cell, whatever kinds of things that you imagine life might have formed out of on earth initially," Culberg said.
There is plentiful opportunity for future research on Europa and Greenland will continue to provide a useful comparison, Culberg said. Future missions in space may allow researchers to confirm their findings.
“The idea that we have Greenland as sort of an analog for some of these processes means that we have that big data record there to see if there are other things we can understand about Europa,” Culberg said. “Someday we’ll actually hopefully get to test some of these hypotheses.”
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