An alien world with a seemingly sulphur-filled atmosphere may be the most volcanic planet astronomers have ever spotted.
We have never directly detected volcanic activity outside our solar system, in part because current telescopes aren’t powerful enough to take images of exoplanets’ surfaces. We might be able to spot alien volcanoes by measuring the gases they pump into a planet’s atmosphere, but this is also at the very limit of what current telescopes can do – there have been tantalising hints of atmospheres on rocky exoplanets, but they have always disappeared in follow-up observations.
Now, at NASA’s Jet Propulsion Laboratory in California and his colleagues think they have seen strong evidence of an atmosphere made almost entirely of sulphur dioxide on the distant world L 98-59 b, a rocky planet less than half the mass of Earth, using new observations from the James Webb Space Telescope (JWST).
Advertisement
That amount of sulphur, if confirmed, implies a level of volcanic activity eight times that of Jupiter’s moon Io – the most volcanic object we currently know of – as well as a magma ocean that spreads through the majority of the planet’s interior.
At first, Bello-Arufe and his team calculated that the planet’s close orbit to its parent star should make it extremely hard for it to keep any atmosphere. “However, what makes L 98-59 b special is that it may experience a large amount of tidal heating, which can drive volcanism, constantly replenishing the atmosphere of the planet,” says Bello-Arufe.
Tidal heating happens as gravitational forces pull a planet’s inner material back and forth. The effect causes the unusually large amount of volcanism we see on Io.
Signatures in the light coming from L 98-59 b could also be explained by a lack of atmosphere, but Bello-Arufe and his team found that it better matched a planet with an extremely sulphur dioxide-rich atmosphere.
If confirmed, which should be possible with more observation time with JWST, it would be the first case of an atmosphere around a rocky exoplanet, says at the University of Oxford. However, there are still some mysteries about the observation, such as why there are no traces of other gases in the atmosphere. “You would expect other [elements] as well,” he says.
arXiv
