UI scientists’ geological discovery indicates possible habitable world
Europa, one of Jupiter’s moons, may be closer to being habitable than most planets in the solar system.
Image of Europa’s surface
Courtesy of Tara Roberts
Louise Prockter of Johns Hopkins University and Simon Kattenhorn, who until recently was a professor at the University of Idaho, released a study this month, indicating that Europa has a plate tectonic system similar to Earth’s.
Kattenhorn, who works in structural geology, said he became interested in Europa when NASA’s Galileo Mission started sending back images of Jupiter’s moon.
“So when I saw these images in the late 90s of Europa, I just realized that there was a wealth of potential research projects that could involve looking at Europa in my field of expertise,” Kattenhorn said. “And so that was the start of what has so far been 16 years of research, and trying to unravel the mysteries of why Europa’s surface looks the way it does.”
He said he and Prockter started studying the images of the Galileo Mission sent back by examining the low-resolution pictures for recognizable features.
“So this began essentially a two-year process of very detailed mapping of the features on the surface, and looking for evidence of what these features could be,” he said. “And this ultimately led to the hypothesis that we were dealing with subduction of one icy plate beneath another one, and so this essentially then made us realize that this would mean that Europa would in fact have the equivalent of a plate tectonic process.”
The plates in a plate tectonic system, which in Earth’s case are made of rock, rest on the outside of a liquid center — Earth’s is made of molten rock — and can move in three ways.
They can move away from each other, causing the space between to fill with new material. Two plates can move next to each other along fault lines, causing earthquakes and volcanic eruptions. Finally, in a process called subduction, two plates can push toward each other, causing one to move beneath the other and into the liquid center.
“On Europa, of course, we’re not dealing with rock, we’re dealing with ice, and so people may wonder how you can have plate tectonics in ice,” he said. “But in many ways, it’s similar to what we see on Earth.”
Kattenhorn said Europa has an outer layer that is about 280 degrees Fahrenheit from its contact with space, while the bottom layer is considered “warm ice,” at about 32 degrees. He said Europa has liquid water beneath the ice shell, which acts the same way as Earth’s rock core.
“Now in this new study that we have just published we have
found evidence of subduction, where one of the plates collides with an adjacent plate, and dives downward beneath it back into the middle of the ice,” he said. “So it essentially moves downward into the ice shell, and is reincorporated into the ice as it warms up.”
He said the discovery of another world with evidence of plate tectonics is exciting, because it allows for Europa to potentially be habitable.
Kattenhorn said subduction would make it possible for Europa’s structure to change.
“Subduction provides a mechanism to get those compounds that are sitting on the surface back down into the ice shell, and potentially reincorporating those compounds into the beneath or perhaps within bodies of water within the ice shell, if they exist,” he said. “And so, for astrobiologists who study such things — habitable environments — this would be very exciting, because it provides a mechanism to introduce the things you need into a habitable environment.”
Daphne Jackson can be reached at [email protected]