Webb Telescope Spots Carbon on Europa's Surface
The search for extraterrestrial life took a significant step forward recently when NASA’s James Webb Space Telescope (JWST) detected carbon dioxide on the frozen surface of Europa. This moon of Jupiter has long been a prime candidate in the search for life due to the vast ocean of salty water hiding beneath its icy shell. The crucial detail in this new discovery is not just that carbon exists there, but where it likely came from: the subsurface ocean itself.
The Discovery at Tara Regio
Astronomers have known for years that Europa possesses a global ocean containing more water than all of Earth’s oceans combined. However, proving that this ocean contains the necessary chemicals to support life has been difficult from millions of miles away.
Using the Webb telescope’s Near-Infrared Spectrograph (NIRSpec), scientists identified a concentration of crystalline carbon dioxide ice. The CO2 was not distributed evenly across the moon. Instead, it was concentrated in a specific region known as Tara Regio.
Tara Regio is what geologists call “chaos terrain.” This is an area where the moon’s smooth, icy crust has been disrupted, cracked, and resurfaced. The geology suggests that relatively warm water from the ocean below has welled up to the surface, breaking the ice sheet. Because the carbon dioxide is concentrated here—in geologically young terrain—scientists are confident the carbon originated from the internal ocean rather than being delivered by crashing meteorites or asteroids.
Why Carbon is the Key to Habitability
Finding water is only step one in assessing whether a celestial body can support life. To be considered habitable, an environment generally needs three things:
- Liquid water
- Energy sources (like thermal vents)
- Chemical building blocks
Carbon is the most critical of these building blocks. It is the backbone of all known life forms. Before this discovery, scientists could not confirm if Europa’s ocean contained carbon. The detection of endogenous carbon—carbon that comes from within the moon—suggests that the ocean has a chemistry complex enough to potentially support biological processes.
In two independent papers published in the journal Science in September 2023, teams led by Geronimo Villanueva of NASA’s Goddard Space Flight Center and Samantha Trumbo of Cornell University detailed these findings. They confirmed that the CO2 is unstable on Europa’s surface, meaning it would likely break down over time. Its presence implies it was deposited there recently on a geological timescale, further supporting the theory of an exchange between the ocean and the surface.
Webb vs. Previous Telescopes
The Hubble Space Telescope had previously observed Europa, but it lacked the specific infrared capabilities required to make this definitive identification. The James Webb Space Telescope sees the universe in infrared light, which allows it to identify the chemical “fingerprints” of substances that are invisible to the human eye or other telescopes.
The observations required only a few minutes of telescope time, demonstrating Webb’s immense power. The specific absorption features of carbon dioxide are very distinct in the infrared spectrum, allowing the teams to map exactly where the CO2 was located and correlate it with the chaos terrain of Tara Regio.
Implications for the Europa Clipper Mission
This discovery comes at a perfect time for NASA’s next major planetary mission. The Europa Clipper spacecraft is scheduled to launch in October 2024 and arrive at the Jupiter system in 2030.
Before the Webb findings, mission planners viewed the investigation of the ocean’s chemistry as a general goal. Now, they have a specific target. The Clipper mission can focus its instruments on Tara Regio and other chaos terrains to analyze this carbon up close. The spacecraft will perform nearly 50 flybys of the moon, flying as close as 16 miles from the surface.
While Webb can see the chemical signature from a distance, Europa Clipper will carry mass spectrometers and dust analyzers that can “taste” the atmosphere and surface particles. The combination of Webb’s distant mapping and Clipper’s close-up analysis will give humanity its best chance yet of determining if Europa is truly habitable.
Frequently Asked Questions
Does this discovery mean there is life on Europa? No, this does not confirm life. It confirms that the ocean contains carbon, which is a necessary ingredient for life as we know it. It means the ocean is “habitable,” or capable of supporting life, but it does not prove anything is currently living there.
Why is the location of the carbon important? If the carbon were spread evenly across the moon, it might have come from external sources like meteorites. Because it is concentrated in “chaos terrain”—areas where the ice has recently broken and mixed with the water below—it indicates the carbon came from the ocean itself.
What is the difference between this and finding water on Mars? Water on Mars is mostly locked in ice caps or underground. Europa has a verified, global, liquid saltwater ocean. Finding carbon in that ocean makes it chemically similar to Earth’s oceans, making it a stronger candidate for finding simpler forms of life.
Will the Europa Clipper land on the moon? No, the Europa Clipper is an orbiter. It will orbit Jupiter and perform close flybys of Europa to scan the surface. A future mission, potentially the Europa Lander, would be required to touch down and dig into the ice.