As well as looking out into distant star systems, the James Webb Space Telescope also observes targets right here in our own solar system — and recently it has made an intriguing discovery about Europa, the moon of Jupiter. Europa is a location of great interest to scientists because it is one of the most likely places in the solar system to support life beyond Earth, and new findings could make that possibility more likely.
From orbit, Europa appears icy, but previous observations like those made by Hubble in 2012 showed that there were plumes of water erupting from the surface — suggesting that there is a liquid water ocean beneath the thick, icy crust. This salty ocean is a prime target for habitability research, but it wasn’t known whether this ocean contained the carbon-related materials that are needed for life.
The new observations using Webb’s NIRSpec instrument found carbon dioxide on the planet’s surface, and the researchers believe that this came from the ocean beneath the icy crust. This supports the idea that there are carbon compounds in this ocean, which could mean it is habitable.
“On Earth, life likes chemical diversity — the more diversity, the better. 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 whether it might be a good place for life,” said one of the researchers, Geronimo Villanueva of NASA’s Goddard Space Flight Center, in a statement.
The researchers considered whether the carbon dioxide they observed could have come from another source other than the subsurface ocean, such as being carried by a meteorite that struck the moon. However, carbon dioxide is unstable on the moon’s surface which implies that it must have arrived there relatively recently. The detection was also made in a particular region of the moon where there is younger terrain, so it is unlikely that the source could have been an ancient meteorite impact.
“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,” said fellow researcher Samantha Trumbo of Cornell University.
Finding carbon molecules is exciting, but it is a long way from confirming that Europa is habitable. For more information, we’ll need in-depth observations like those that will be collected by the JUICE and upcoming Europa Clipper missions. Eventually, the ideal scenario would be to send a mission that can pass through the surface and probe the ocean itself.
“Scientists are debating to what extent 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.”
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