Astronomers have discovered a large deposit of carbon dioxide (CO2) ice on Europa, one of the icy moons of Jupiter. The distant world is covered by a thick ice crust and beneath it there is a salty water ocean and a rocky seafloor. Europa is already seen as one of the most likely possible places where life could emerge. However, scientists weren’t even sure its ocean contained the chemicals like CO2 needed for life. This has now changed.
Observations from JWST revealed the presence of carbon dioxide on the surface of Europa consistent with coming from the ocean underneath the ice rather than delivered by meteorites. This discovery has important implications for the possible habitability of Europa.
“On Earth, life likes chemical diversity – the more diversity, the better," Geronimo Villanueva of NASA’s Goddard Space Flight Center, lead author of one of two independent papers describing the findings, said in a statement. "We’re carbon-based life. Understanding the chemistry of Europa’s ocean will help us determine whether it’s hostile to life as we know it, or if it might be a good place for life.”
“We now think that we have observational evidence that the carbon we see on Europa’s surface came from the ocean. That's not a trivial thing. Carbon is a biologically essential element,” added Samantha Trumbo of Cornell University, lead author of the second paper.
Carbon dioxide is not stable on the surface of Europa. This means it had to have reached it in a geologically recent timescale. Its highest abundance was found in the Tara Regio, an area known for its resurfaced "chaos terrain". Previous observations have confirmed that the surface ice had been disrupted, and there had been an exchange between the ocean and the surface.
“Previous observations from the Hubble Space Telescope show evidence for ocean-derived salt in Tara Regio,” explained Trumbo. “Now we’re seeing that carbon dioxide is heavily concentrated there as well. We think this implies that the carbon probably has its ultimate origin in the internal ocean.”
“Scientists are debating how much Europa’s ocean connects to its surface. I think that question has been a big driver of Europa exploration,” said Villanueva. “This suggests that we may be able to learn some basic things about the ocean’s composition even before we drill through the ice to get the full picture.”
The observations did not report any plume activity, like the geysers seen on Enceladus, the equally icy moon of Saturn. This doesn’t mean that Europa doesn’t have such activity only that during the time JWST dedicated to the moon, they did not see any.
Future missions like the European Space Agency’s JUICE and NASA’s Europa Clipper will provide more insight on this intriguing world and these new observations will influence what these missions will look for.