Scientists find gas attributed to living things on Earth on Venus

PARIS • The atmosphere of Venus contains a gas that on Earth can be attributed to living organisms, scientists have said. It is a discovery the head of the National Aeronautics and Space Administration (Nasa) called "the most significant development yet" in the hunt for extraterrestrial life.

Conditions on Earth's planetary neighbour are often described as hellish with daytime temperatures hot enough to melt lead and an atmosphere comprised almost entirely of carbon dioxide. However, a team of experts detected traces of phosphine, a flammable gas that on Earth often occurs from the breakdown of organic matter. They used telescopes in Hawaii and Chile's Atacama Desert to observe Venus' upper cloud deck, around 60km from the surface.

Writing in Nature Astronomy on Monday, the team stressed the presence of phosphine did not prove the presence of life on Venus. But, as the clouds swirling about its broiling surface are highly acidic and therefore destroy phosphine very quickly, the research did show that something was creating it anew.

The researchers conducted several modelling calculations in a bid to explain the new phosphine production. They concluded that their research provided evidence "for anomalous and unexplained chemistry" on Venus.

The breakthrough was hailed by Nasa administrator Jim Bridenstine, who tweeted, "it's time to prioritise Venus".

Other planetary scientists counter that a non-biological origin cannot be ruled out. "Despite prior speculation (mostly by the same authors), this can hardly be taken as a biosignature," Dr Gerald Joyce, a biologist at the Salk Institute in California, said in an e-mail.

The bulk of current efforts to look for past extraterrestrial life focuses on Mars, known to have once contained all the necessary ingredients to support carbon-based organisms. The United States and China recently sent rovers to the Red Planet, while the United Arab Emirates sent an atmospheric probe.

Venus, which rotates in the opposite direction to Earth and where a day lasts 243 times longer, is a subject of intense interest among astronomers. It is so close and of such similar size to Earth that some experts believe it serves as a warning of the dangers of runaway climate change.

Previous studies have unearthed tantalising clues suggesting Venus has active volcanoes, including signs of recent lava flows.

AGENCE FRANCE-PRESSE, NYTIMES