Scientists using the Webb Space Telescope have identified a molecule in the atmosphere of another planet that could potentially be a sign of life.
During only two observations, evidence of dimethyl sulfide (DMS) was found in the atmosphere of K2-18 b, a giant “sub-Neptunian” planet about 120 light years from the Solar System in the Leo constellation.
On Earth, DMS is primarily a by-product of phytoplankton. However, according to the authors of a paper yet to be published, the finding is preliminary and “requires further verification”. The Astrophysical Journal Letters,
“Upcoming Webb observations should be able to confirm whether DMS is indeed present at significant levels in the atmosphere of K2-18 b,” said Nikku Madhusudan, an astronomer at the University of Cambridge and lead author of the paper.
The researchers analyzed light from K2-18 b’s host star as it passed through the exoplanet’s atmosphere. Webb’s unique ability to see in the infrared was important, as well as its incredible sensitivity.
The ultimate goal of this work is to identify life on a habitable exoplanet.
This is not the first time that K2-18 b has made headlines. An exoplanet 8.6 times larger than Earth orbiting a cool red dwarf star called K2-18 was discovered by NASA’s Kepler Space Telescope in 2015. Here’s why this is exciting:
- It is located in the star’s habitable zone – an orbit around a star close enough to make liquid water possible on the surface of a rocky planet.
- In 2019, the Hubble Space Telescope found evidence of water vapor in its atmosphere.
- The new research also revealed the presence of carbon-bearing molecules, including methane and carbon dioxide.
- The abundance of methane and carbon dioxide and lack of ammonia suggest that there may be an ocean beneath the hydrogen-rich atmosphere – a so-called “hycene” exoplanet.
However, not only does its mass mean that its surface gravity will be significantly greater than Earth’s, but the host star K2-18 is thought to be highly active. The surface of K2-18b is therefore likely to be repeatedly drenched with high-energy radiation, creating an environment inhospitable to life. It is also likely that the planet’s interior consists of a large blanket of high-pressure ice, like Neptune, and any oceans are too warm to be habitable.
“Our findings underline the importance of considering diverse habitable environments in the search for life elsewhere,” Madhusudan said. “Traditionally, the search for life on exoplanets has focused primarily on small rocky planets, but large Hyssene worlds are quite amenable to atmospheric observations.”
what happens next
Although there are no examples of it in our Solar System, sub-Neptunes appear to be the most common type of planet in the galaxy.
More observations of K2-18 b are planned with Webb’s mid-infrared instrument, said team member Savvas Constantino, of the University of Cambridge, who added: “This means our work here will expand what Webb can see in the habitable zone. It is an early demonstration of exoplanets.”
Wishing you clear skies and wide eyes.