For as long as humans have looked up at the night sky, we have been curious about life beyond Earth. Scientists now know that there are several places in the solar system that may have conditions suitable for life. One of these is Jupiter's moon Europa, a fascinating world with a salty subsurface ocean of liquid water -- perhaps twice as much liquid water as all Earth's oceans combined. However, scientists have yet to confirm whether Europa's ocean contains chemicals necessary for life, especially carbon - the universal building block of life as we know it.

Now, astronomers using the James Webb Space Telescope have discovered carbon on the surface of Europa, and the carbon likely originated from this ocean. The discovery hints at the possibility of habitable environments in Europa's ocean.

The blue-white sphere on a black background is reminiscent of the famous "Blue Marble" photo of Earth from space. The sphere's edges are blurred and diffuse, with much of the northern hemisphere facing the observer appearing as patches of dark blue. A large crescent-shaped white patch runs along the left side of the Southern Hemisphere facing the observer, and a larger, spherical white patch covers the mid-latitudes on the right side of the Southern Hemisphere. Light blue areas border these white patches in the Southern Hemisphere.

Jupiter's moon Europa is one of the few worlds in the solar system that could harbor life. Previous research has shown that beneath its water-ice crust lies a salty liquid water ocean and a rocky seafloor. However, planetary scientists have yet to confirm whether this ocean contains the chemicals needed for life, especially carbon.

Astronomers using data from NASA's James Webb Space Telescope discovered carbon dioxide in a specific area of ​​Europa's ice surface. Analysis showed that the carbon likely came from an underground ocean rather than being provided by meteorites or other external sources. Furthermore, its deposition is geologically recent. This discovery has important implications for the potential habitability of Europa's ocean.

"On Earth, life loves chemical diversity - the more diversity the better. We are carbon-based life. Understanding the chemistry of Europa's ocean will help us determine whether it is hostile to life as we know it, or whether 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 separate papers describing the discovery.

"We now believe that we have observational evidence that the carbon we see on Europa's surface comes from the ocean. This is no small thing. Carbon is an essential element for living things," added Samantha Trumbo of Cornell University in Ithaca, New York, and lead author of a second paper analyzing the data.

NASA plans to launch the Europa Clipper spacecraft. The spacecraft will conduct dozens of close flybys of Europa to further study whether Europa has conditions suitable for the existence of life.

Surface-to-ocean connection

Weber discovered that the area with the highest carbon dioxide content on the surface of Europa is an area called the "Tara Regio". The surface ice has been disrupted, and there is likely to have been an exchange of material between the underground ocean and the ice surface.

"Previous observations with the Hubble Space Telescope showed evidence of salt extraction from the ocean at Tara Riggio. Now we see large concentrations of carbon dioxide there as well. We think that means the carbon may have ultimately originated from the internal ocean," Trumbo explained.

"Scientists are debating how much Europa's ocean is connected to its surface. I think that question has been a big driver of Europa exploration," Villanueva said. "This suggests that even before we drill through the ice to get the full picture, we may be learning something fundamental about the composition of the ocean."

The two teams determined carbon dioxide using data from the Webb Near Infrared Spectrograph (NIRSpec) Integrated Field Unit. This instrument mode can provide spectra with a resolution of 200x200 miles (320x320 kilometers) across the 1,944-mile-diameter surface of Europa, allowing astronomers to determine the location of specific chemicals.

Carbon dioxide is not stable on Europa's surface. Therefore, the scientists say, the carbon dioxide was likely supplied in recent geological time - a conclusion reinforced by the concentration of carbon dioxide in an area of ​​young terrain.

Heidi Hammel of the Association of Universities for Research in Astronomy said: "These observations only took up a few minutes of the observatory's time, and even in this short time, we were able to complete very important scientific work. This work provides the first clues to all the amazing solar system science we can do with the Webb telescope." She is a Webb interdisciplinary scientist who leads Webb's first cycle-guaranteed time observations of the solar system.

Villanueva's team also looked for evidence of water vapor plumes erupting from Europa's surface. Researchers using NASA's Hubble Space Telescope reported preliminary detections of plumes in 2013, 2016, 2017 and 2018. However, finding conclusive evidence has been difficult.

The new Webb data showed no evidence of plume activity, allowing Villanueva's team to place a tight upper limit on the rate at which material could be ejected. However, the team emphasized that the lack of detection does not rule out the possibility of a plume.

"It's always possible that these plumes are variable and that you only see them at certain times. We can say with 100 percent certainty that we did not detect plumes at Europa during our observations with the Webb telescope," Hamel said. The findings could help inform NASA's Europa Clipper mission and the European Space Agency's (ESA) upcoming Jupiter Icy Moon Explorer (JUICE).

The two papers will be published in the journal Science on September 21.

The James Webb Space Telescope is the world's most important space science observatory. Webb is unraveling the mysteries of the solar system, peering into distant worlds around other stars, and exploring the mysterious structure and origins of the universe and our place in it. The Webb telescope is an international program led by NASA with partners including the European Space Agency (ESA) and the Canadian Space Agency.