Europa’s subsurface ocean is the likely source of carbon dioxide detected on its surface, marking a major leap in understanding the potential for Jupiter’s sixth-closest moon to harbour life.
The discovery was made by astronomers embedded in NASA’s James Webb Space Telescope program.
It’s long been known that below Europa’s protective ice sheet is a liquid water ocean and rocky seabed, like Earth.
Solid carbon dioxide has been previously identified on the moon’s surface, but until now, it’s been difficult to know what other chemicals exist within its subsurface ocean.
“On Earth, life likes chemical diversity – the more diversity, the better. We’re carbon-based life,” says Dr Geronimo Villanueva, a planetary scientist at NASA’s Goddard Space Flight Center.
“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.”
Villanueva’s team used the James Webb Space Telescope to analyse its surface and found carbon dioxide in a region called Tara Regio using the Near-Infrared Spectrograph. With a 320×320 kilometre resolution, this imager can identify the location of specific chemicals on Europa’s surface.
Peering at Tara Regio, the JWST identified specific regions of solid carbon dioxide in a region of disrupted surface ice.
This, says Villanueva, indicates a connection between the surface and subsurface ocean.
“Previous observations from the Hubble Space Telescope show evidence for ocean-derived salt in Tara Regio,” says Dr Samantha Trumbo, an astronomer from Cornell University, US, whose analysis of Europa’s carbon has been published in Science.
“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.”
While identifying solid carbon and a potential connection to Europa’s ocean isn’t indicative of life, the discovery of this connection is a vital step towards understanding the moon’s potential.
“[It’s] not a trivial thing. Carbon is a biologically essential element,” says Trumbo.
Further close-up analyses of Europa are scheduled to take place at the end of the decade, with NASA’s Europa Clipper mission to launch towards Jupiter next year and the European Space Agency’s JUICE spacecraft which launched in April, will get close-up to Europa in 2030.