On Jupiter’s moon Europa, ‘chaotic terrain’ could carry oxygen to the ocean

According to a team of researchers led by the University of Texas at Austin, the salty water contained in the icy shell of Europa, the moon of Jupiter, could transport oxygen in an ocean of liquid water covered in ice where it could potentially help sustain extraterrestrial life.

This theory has been proposed by others, but the researchers put it to the test by building the world’s first physics-based computer simulation of the process, with oxygen hitching a ride on salt water under the “chaotic terrains” of the moon, landscapes composed of fissures, ridges and blocks of ice that cover a quarter of the icy world.

The results show that not only is transport possible, but that the amount of oxygen brought into the ocean of Europa could be equivalent to the amount of oxygen in Earth’s oceans today.

“Our research puts this process within the realm of possibility,” said lead researcher Marc Hesse, a professor in the Department of Geological Sciences at UT Jackson School of Geosciences. “It provides a solution to what is considered to be one of the outstanding problems of the habitability of Europe’s subterranean ocean.”

The study has just been published in the journal Geophysical Research Letters.

Europa is a prime location to search for extraterrestrial life as scientists have detected signs of oxygen and water, as well as chemicals that could serve as nutrients. However, the moon’s icy shell – estimated to be about 15 miles thick – serves as a barrier between water and oxygen, which is generated by sunlight and charged particles from Jupiter hitting the surface. icy.

If life as we know it exists in the ocean, there must be a way for oxygen to get there. According to Hesse, the most plausible scenario based on the available evidence is that the oxygen is transported by salt water or brine.

Scientists believe that chaotic terrains form over regions where Europa’s ice shell partially melts to form brine, which can mix with oxygen from the surface. The computer model created by the researchers showed what happens to the brine after the chaotic terrain forms.

The model showed that the brine flowed in a distinct way, taking the form of a “porosity wave” that causes the pores of the ice to momentarily widen, allowing the brine to pass through before settling. close. Hesse compares the process to the classic comic book gag of a water bulge coming down a garden hose.

This mode of transport appears to be an efficient way to deliver oxygen through the ice, with 86% of the oxygen being absorbed at the surface traveling the wave to the ocean. But available data allow for a wide range of oxygen levels delivered to Europa’s ocean over its history – with estimates ranging by a factor of 10,000.

According to co-author Steven Vance, a researcher at NASA’s Jet Propulsion Laboratory (JPL) and supervisor of its Planetary Interiors and Geophysics group, the higher estimate would make oxygen levels in Europa’s ocean similar to those in Earth’s oceans – raising hopes for the potential of this oxygen to support life in the Hidden Sea.

“It’s tempting to think of some kind of aerobic organisms living just under the ice,” he said.

Vance said NASA’s next Europa Clipper mission in 2024 could help improve estimates of oxygen and other ingredients needed for life on the icy moon.

Kevin Hand, a Europa scientist at NASA JPL who was not part of the study, said the study presents a compelling explanation for oxygen transport on Europa.

“We know that Europa has useful compounds like oxygen on its surface, but do these end up in the ocean below, where life can use them?” he said. “In the work of Hesse and his collaborators, the answer appears to be yes.”

The research was funded by NASA, the National Science Foundation and the American Chemical Society Petroleum Research Fund.

In addition to the Jackson School, Hesse is also a research fellow at the UT Center for Planetary Systems Habitability and the Oden Institute for Computational Engineering and Sciences.

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