Webb Telescope’s search for life on distant exoplanet faces challenges

Artist rendering of the view on a Hycean world. Credit: Shang-Min Tsai/UCR.

Recent excitement about NASA’s James Webb Space Telescope (JWST) potentially finding signs of life on a distant planet has been tempered by a new study.

Although the telescope detected intriguing gases on the exoplanet K2-18b, researchers at the University of California, Riverside (UCR) suggest that these findings might not conclusively point to life.

Their research, detailed in The Astrophysical Journal Letters, explores how future observations could confirm the presence of life-produced gases.

K2-18b, located about 120 light years away from Earth, is an exoplanet that receives a similar amount of solar radiation as Earth, making it a candidate for supporting life.

Unlike Earth’s nitrogen-rich atmosphere, K2-18b has a hydrogen-based atmosphere and is speculated to have vast water oceans.

This unique combination makes K2-18b a “Hycean” world, a potential home for life that differs from what we find on Earth.

In 2023, a team from Cambridge used the JWST to identify methane and carbon dioxide in K2-18b’s atmosphere—gases that on Earth are associated with biological activity.

The researchers also reported a possible detection of dimethyl sulfide (DMS), a compound produced by ocean phytoplankton on Earth and crucial for cloud formation. However, the detection was tentative and not definitive.

Shang-Min Tsai, a UCR project scientist and author of the study, explained that while the initial findings were promising, the data from JWST did not strongly support the presence of DMS.

This is because the DMS signal could easily be confused with methane, another prevalent gas in K2-18b’s atmosphere.

The UCR team’s computer models, which simulate the physics and chemistry of DMS in a hydrogen-based atmosphere, indicated that detecting DMS at significant levels would require life forms on K2-18b to produce much more DMS than is typical on Earth.

Despite these challenges, the researchers are hopeful about future observations with JWST. Later this year, the telescope is scheduled to use an upgraded instrument better suited for detecting DMS and other potential signs of life.

This could provide clearer evidence about the presence of life on K2-18b or similar planets.

Eddie Schwieterman, a UCR astrobiologist and senior author of the study, noted that the best signs of life on an exoplanet might differ greatly from those on Earth.

For example, DMS could be a more prominent biosignature in hydrogen-rich atmospheres compared to oxygen produced by plants and bacteria on Earth.

The ongoing quest to find life beyond Earth is driven by curiosity and the human instinct to explore the unknown.

Tsai likened it to hearing a noise while camping in the wilderness and using a flashlight to see what’s out there. In the case of astronomers, they use telescopes to shed light on the mysteries of the cosmos.