Opinion Search for life outside Earth has received a boost with the James Webb Telescope

The volatile sulphur compound, dimethyl sulphide (DMS), gives the sea its distinctive odour. It is produced by blooms of algae floating close to the sea surface and is regarded by scientists as a biosignature — an indication of the possibility of life. Last week, a paper published in the Astrophysical Journal Letters suggested an abundance of DMS on a planet, K2-18b, that orbits a star 124 light years from Earth. The study led by Cambridge scientist Nikku Madhusudhan suggests that the DMS concentrations on the planet are thousands of times stronger than on Earth. The scientists used data from the James Webb Telescope to generate the strongest indication, so far, of life outside the only habitable planet. However, much more research is required to reach the grand conclusion that there are oceans outside the solar system, teeming with life.

K2-18b was discovered in 2015 by NASA’s Kepler mission, prompting studies that have changed the understanding of the universe. It is amongst the planets outside the solar system that are far bigger than Earth but smaller than Neptune. These sub-Neptunes are located around the “Goldilocks Zone” of a star, an area not too hot and not too cold to contain water, and, therefore, holding the promise of life. But even now sub-Neptunes are poorly understood. The dazzle of its parent star outshines the planet, making it difficult to explore its atmosphere. Researchers from Madhusudhan’s team sidestepped this challenge by analysing the light from the planet’s parent star as it passed through the sub-Neptune’s atmosphere. In 2023, Madhusudhan’s team had identified methane and carbon dioxide in K2-18b’s atmosphere. That study found a “tantalising hint of DMS”, but the Astrophysical Journal Letters study offers a stronger indication of the gas. Scientists will now need to run several studies to make sense of the latest findings. For instance, one question that needs to be answered is if DMS behaves in the same manner as it does on Earth.

Advertisement

The search for life outside Earth has been a longstanding pursuit in astronomy. It received a fillip with the launch of the James Webb Telescope in 2021, which can analyse the chemical composition of a planet’s atmosphere from the light of the star it orbits. However, the most powerful telescope in human history can only detect large faraway planets such as K2-18b. NASA has plans to develop an observatory that can spot the atmosphere of distant planets as small as Earth. The Trump administration’s clampdown on the agency’s funding could, however, jeopardise, at least temporarily, the plans to further extend the boundaries of human knowledge.