Nearby planet reeks of rotten eggs
The smell is from hydrogen sulphide, a vital ingredient for building the molecules of life
It’s rare that discovering a place that smells of rotten eggs is a cause for celebration, but that’s the case with exoplanet HD 189733 b. Observations of the planet’s atmosphere by the James Webb Space Telescope (JWST) found traces of hydrogen sulphide, the chemical which gives bad eggs their odour and which is an important ingredient in the formation of life.
“We’re not looking for life on this planet – it’s way too hot,” says Guangwei Fu from Johns Hopkins University, who led the study. “But finding hydrogen sulphide is a stepping stone for finding this molecule on other planets and gaining more understanding of how different types of planets form.”
HD 189733 b is far from a pleasant place to visit, quite aside from its odour – the temperature is around 930°C (1,700°F), it rains glass and the wind blows up to 8,000km/h (5,000mph). Located 64 lightyears away, the planet is slightly larger than Jupiter but orbits its star 13 times closer than Mercury orbits the Sun. Fu’s team used JWST to characterise the planet’s atmosphere, accurately measuring its water, carbon dioxide and carbon monoxide content, as well as uncovering hydrogen sulphide.
“Sulphur is a vital element for building more complex molecules and – like carbon, nitrogen, oxygen and phosphate – scientists need to study it more to fully understand how planets are made and what they’re made of,” says Fu.
These elements are the foundation of known life and even though HD 189733 b is uninhabitable, knowing their abundance gives an insight into their presence on other planets which may be more hospitable to life. They also have a major impact on the planet’s atmosphere and chemistry. Fu’s team will now attempt to sniff out traces of sulphur on further exoplanets, to build a picture of how the element is distributed on other worlds. hub.jhu.edu