CO2 from the moon Europa originated in its inner ocean

Portada Carbono en Europa

Jupiter's moon Europa is an essential target in the search for life elsewhere in the solar system because a subsurface ocean of salty liquid water is believed to lie beneath a frozen crust of solid ice. The potential habitability of that hidden environment depends on its chemical composition, including the abundance of biologically essential elements such as carbon.

The CO2 on the surface of the moon Europa originated in its interior ocean
Jupiter's icy moon Europa captured in 2022 by NASA's Juno probe. / NASA/JPL-Caltech/SwRI/MSSS Image processing: Kevin M. Gill

Previous research has detected the presence of solid CO ice2 on the surface of Europa, but until now it has not been possible to determine whether that carbon dioxide originated in the underground ocean, if it reached the moon due to the impact of meteorites or if it occurred on the surface through interactions with the magnetosphere of the gigantic Jupiter. The first option seems to be the correct one, according to two studies published this week in the journal Science.

Two independent studies have used data from the James Webb telescope to verify that the CO2 in Europa's surface ice comes from the ocean assumed to lie beneath.

Both works use spectroscopic observations in the near infrared which has registered the James Webb Space Telescope (JWST) on the ice of this moon, and both indicate that its CO2 It comes from the subsurface ocean below.

In one of the articles, the researcher Samantha Trumbo from Cornell University and Michael Brown at Caltech (both in the US) used Webb data to map the distribution of carbon dioxide in Europe and found that it is most abundant in Tara Regio, a region of about 1,800 square kilometers dominated by “chaotic terrain,” geologically altered materials that have recently returned to the surface.

CO2 is most abundant in Tara Regio, a chaotic terrain with altered materials that have recently returned to the surface

“This indicates that the CO2 identified in this region – one of the youngest terrains on the surface of Europe – comes from an internal source of carbon, and we propose that it formed in the internal ocean,” the authors point out. Afterwards, it would have emerged into the outer zone on a geologically recent time scale.

However, they do not rule out another option: “a formation on the surface through the radiolytic conversion of organic compounds or carbonates derived from the ocean.” In either case, the underground ocean would contain carbon.

Same conclusion in another study

For its part, another team independent of scientists, led by Geronimo Villanueva from NASA's Goddard Center, used the same Webb data to detect “four spectral features of CO ice2, with shapes and distribution over the surface of Europa that indicate that it is mixed with other compounds and concentrated in Tara Regio.”

 
graph 3
CO2 distribution on the moon Europa: false color image captured by JWST and three models of carbon dioxide intensity bands. / GL Villanueva et al./Science

The authors also measured the ratio of two carbon isotopes, specifically 12C/13CO Ice C2, and with the value obtained (83) and other observations “we interpret that the carbon comes from the interior of Europe.” However, they could not distinguish whether its source is abiotic (by geological processes, for example) or biogenic, that is, produced by some possible form of life.

In search of the plumes

In addition, they looked for feathers or plumes of volatile material that crossed the frozen crust of the Moon. Although indications of these characteristics had been found in previous studies, the authors did not find them during the Webb observations: “In the search for plumes, no water, carbon monoxide, methanol, ethanol, or fluorescent methane emissions were detected.”

The researchers argue that the activity of these emanations of material on Europa could be infrequent, or that they sometimes do not contain the volatile gases that they included in their searches with the space telescope.

Carbon in the lunar ocean

In any case, the results of both studies complement each other and reinforce the conclusion that the subsurface ocean of Europe contains abundant carbon.

“On Earth, life likes chemical diversity: the more diversity, the better. Are carbon based life. Understanding the chemistry of Europa's ocean will help us determine if it is hostile to life as we know it or if it could be a good place for it," says Villanueva.

For his part, Trumbo adds: “We now believe we have observational evidence that the carbon we see on its surface comes from the ocean. It is not something trivial. Carbon is a biologically essential element”.

NASA plans to launch its spacecraft in October 2024 Europa Clipper, which will make dozens of close flybys of this moon of Jupiter to continue investigating whether it could have conditions suitable for life.

Reference:

Samantha K. Trumbo et al. “The distribution of CO2 in Europe indicates an internal source of carbon”. GL Villanueva et al. “Endogenous CO2 ice mixture on the surface of Europa and no detection of plume activity.” Science, 2023

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Octavio Alonso