Will scientists searching for signs of life elsewhere in the solar system live to regret their decision recently to send NASA to Saturn’s moon Enceladus instead of Jupiter’s moon Europa?
Both moons are known to have saltwater oceans under their thick icy surfaces and both appear to have geysers that send some of that water—as vapor—into space. The recent Decadal Survey for Planetary Science and Astrobiology decided that the plumes at Enceladus were more reliable and easier to sample than those at Europa, so overlooked the $5.8 billion Europa Lander mission in favor of the $4.9 billion Enceladus Orbilander.
Now it looks like Europa has may have an abundance of “water pockets” just beneath its icy shell—and possibly oxygen in its ocean.
Published in NatureCommunications, a new study used ice-penetrating radar in Greenland. They did so because they noticed that ridges on the icy moon looked extremely similar to a minor feature on the surface of the Greenland ice sheet, which they had already studied in detail.
Chemicals from space?
It suggests that Europa’s ice shell may not be a barrier to exploration, but actually a more dynamic place that could itself be habitable.
“Because it’s closer to the surface, where you get interesting chemicals from space, from other moons and from the volcanoes of another moon of Jupiter called Io, there’s a possibility that life has a shot if there are pockets of water in the shell,” said Dustin Schroeder, senior author of the study and an associate professor of geophysics at Stanford University’s School of Earth, Energy and Environmental Sciences. “If the mechanism we see in Greenland is how these things happen on Europa, it suggests there’s water everywhere.”
The researchers were actually working on climate change science when they noticed that an M-shaped crest in Greenland could be a miniature version of an obvious feature on Europa.
You can see them in any image of Europa—such as this one, below, as dramatic gashes across the icy surface. They reach nearly 1,000 feet and are separated by valleys about a half-mile wide.
Shallow water pockets on Europa
The above image is actually from NASA’s Galileo orbiter, which was the first spacecraft to spot the features on Europa in the 1990s.
The next major close-up that scientists will get of Europa will be from Juno. In late September 2022 it will get to just 221 miles/355 kilometers) above Europa’s surface.
“In Greenland, this double ridge formed in a place where water from surface lakes and streams frequently drains into the near-surface and refreezes,” said Riley Culberg, lead study author and a PhD student in electrical engineering at Stanford. “One way that similar shallow water pockets could form on Europa might be through water from the subsurface ocean being forced up into the ice shell through fractures—and that would suggest there could be a reasonable amount of exchange happening inside of the ice shell.”
It’s long been thought that Europa is a geologically active and dynamic place. “We are making a much bigger step into the direction of understanding what processes actually dominate the physics and the dynamics of Europa’s ice shell,” said Gregor Steinbrügge, study co-author and planetary scientist at NASA’s Jet Propulsion Laboratory (JPL), who started working on the project as a postdoctoral researcher at Stanford.
But could there be something living in the underground ocean?
Life in Europa’s ocean?
Another recent study of Europa, this time involving computer simulations of its “chaos terrain” surface, was published in Geophysical Research Letters during March 2022. It suggests that oxygen could be hitching a ride on salt water into its subsurface ocean.
In fact, their results show that the amount of oxygen brought into Europa’s ocean could be similar to Earth’s oceans. Cue the possibility of aquatic aerobic organisms.
“Our research puts this process into the realm of the possible,” said lead researcher Marc Hesse, a professor at the UT Jackson School of Geosciences Department of Geological Sciences. “It provides a solution to what is considered one of the outstanding problems of the habitability of the Europa subsurface ocean.”
Two missions to Europe
Although the Europa Lander concept is dead, for now, Europa isn’t being totally ignored. NASA’s Europa Clipper mission will launch in October 2024 and arrive in late 2027 to perform about 45 flybys, in each pass photographing the moon’s icy surface in high resolution.
It may help improve estimates for oxygen and other ingredients for life on the icy moon.
Meanwhile, the European Space Agency’s JUpiter ICy moons Explorer (JUICE) will launch in May 2022, arrive in 2029 and take three and a half years to examine Europa as well as two of Jupiter’s other Galilean moons, Ganymede and Callisto.
Wishing you clear skies and wide eyes.