By Mayank Chhaya-
Europa, one of Jupiter’s likely 95 moons often regarded as the most promising place for life apart from Earth, became even more so with the discovery of carbon originating in its subsurface ocean.
This discovery, which has important implications for the potential habitability of Europa’s ocean, has been made by NASA’s James Webb Space Telescope (JWST).
“Astronomers using data from NASA’s James Webb Space Telescope have identified carbon dioxide in a specific region on the icy surface of Europa. Analysis indicates that this carbon likely originated in the subsurface ocean and was not delivered by meteorites or other external sources. Moreover, it was deposited on a geologically recent timescale,” NASA announced today.
The discovery has excited scientists who have long regarded Europa as the most promising place for life outside earth. Although until recently they knew that beneath its water-ice crust lies a salty ocean of liquid water with a rocky seafloor, they did not know if contained life-supporting chemicals such as carbon.
“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 if it might be a good place for life,” said Geronimo Villanueva of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, lead author of one of two independent papers describing the findings.
“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,” added Samantha Trumbo of Cornell University in Ithaca, New York, lead author of the second paper analyzing these data.
According to NASA, Webb found that on Europa’s surface, carbon dioxide is most abundant in a region called Tara Regio – a geologically young area of generally resurfaced terrain known as “chaos terrain.” “The surface ice has been disrupted, and there likely has been an exchange of material between the subsurface ocean and the icy surface,” it said.
Trumbo was quoted as saying, “Previous observations from the Hubble Space Telescope show evidence for ocean-derived salt in Tara Regio. 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.”
“Scientists are debating how much 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.”
Since carbon is not stable on Europa’s surface its presence indicates that it was supplied on a geologically recent timescale.
Europa has a diameter of 1,944 miles. A NASA backgrounder about Europa says, “Scientists think Europa’s ice shell is 10 to 15 miles (15 to 25 kilometers) thick, floating on an ocean 40 to 100 miles (60 to 150 kilometers) deep. So while Europa is only one-fourth the diameter of Earth, its ocean may contain twice as much water as Earth’s global ocean.”
[Photo Courtesy:Europa by NASA’s Galileo spacecraft in the late 1990s. Credit: NASA/JPL-Caltech]
