That's gas: CO2 found on Europa surface may hint at some possible sign of life

The search for alien life in our Solar System has heated up with the discovery of carbon dioxide on the surface of Europa, the Jupiter moon that is believed to house a massive, salty liquid water ocean beneath its frozen surface.

That's pretty interesting because if there's CO₂ in that ocean, that would mean there's salty water, carbon, and oxygen – building blocks for life as we know it – potentially.

The discovery, as described in a pair of scientific papers published yesterday, was made thanks to the James Webb Space Telescope's near-infrared spectrograph. The find points to carbon dioxide not arriving from external sources, such as meteorites, but rather being raised to the surface of Europa from its internal ocean on a relatively recent timescale, geologically speaking. 

The high levels of CO₂ were found on Europa in a region known as Tara Regio, which is a young region of resurfaced "chaos terrain" that's caused by some sort of disturbance involving "an exchange of material" between the ocean and frozen surface, NASA explained. 

"Previous observations from the Hubble Space Telescope show evidence for ocean-derived salt in Tara Regio," said Cornell University's Samantha Trumbo, lead author on one of the two papers. "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."

JWST readings that found CO₂ on Europa's surface in the Tara Regio region - Click to enlarge

NASA hasn't provided an estimate of how old Tara Regio's surface is compared to the rest of Europa, but believes other observations of the moon rule out exogenic sources. Other moons of Jupiter contain CO₂ that came from other sources, the researchers said, but "none of these scenarios would produce the observed relationship between Europa's CO₂ and its geologically disrupted large-scale chaos terrain," they concluded. 

CO₂ on the surface of Europa doesn't last that long, another sign in favor of it having been ejected to the surface in recent geologic history since most of it is confined to Tara Regio, they argue. 

The second of the two papers was examining whether there could have been plumes of water vapor erupting from beneath Europa's surface, but found no evidence of plume activity - a fact that still doesn't rule it out entirely, the team noted. The absence of any plume did allow the researchers to set an upper limit on the rate of material being ejected from the inner region of Europa, though, so not all was lost. 

Greetings, Europans!

"The presence of CO₂ doesn't directly support the presence of undiscovered life," NASA told us. "It does, however, show that one of the key ingredients for life as we know it is available in the Europan ocean," the space agency added. So don't get your hopes up, but don't consider them dashed, either. 

• Launching soon: ESA's Juice to probe Jupiter's moons for signs of possible life
• James Webb spots water vapor in rocky planet-forming disk
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• Space dust that regularly hits Earth could contain proof of alien life

Carbon beneath the surface is likely in the form of dissolved CO₂, the researchers said, but could also be in other forms. The bottom line is that, if the team is correct, then "carbon, a biologically essential element, is present in Europa's subsurface ocean … if this carbon was delivered as CO₂ and if that CO₂ is representative of the carbon redox state in the ocean then a highly reduce ocean chemistry is unlikely." 

In other words, there's probably oxygen down there, too. 

We'll learn more once the European Space Agency's JUICE mission arrives at Jupiter's moons in a little under eight years, and then once NASA's Europa Clipper mission reaches Europa after its scheduled launch date late next year. Both will study the moons of Jupiter - Europa included - in greater detail than we can do from such a distance - even with the JWST. ®