The planet venus is seen at the start of its transit of the Sun

The atmosphere of Venus contains a gas that on Earth can be attributed to living organisms, scientists said Monday, a discovery the head of NASA called "the most significant development yet" in the hunt for extraterrestrial life.

Conditions on our 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 60 kilometres (45 miles) from the surface.

Writing in Nature Astronomy, 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.

 This artistic impression depicts the planet Venus. 

They concluded that their research provided evidence "for anomalous and unexplained chemistry" on Venus.

Lead author Jane Greaves, from Cardiff University's School of Physics and Astronomy told AFP that the presence of phosphine alone was not proof of life on Earth's next door neighbour.

Greaves added that it was the first time phosphine had been found on a rocky planet other than Earth.

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

The bulk of current efforts to look for past extraterrestrial life focus on Mars, which is known to have once contained all the necessary ingredients to support carbon-based organisms.

The US and China recently sent rovers to the Red Planet, while the UAE sent an atmospheric probe.

'Exciting'

Reacting to the study, Alan Duffy, an astronomer from Swinburne University and Lead Scientist of The Royal Institution of Australia, said it while it was tempting to believe that the phosphine was produced by lifeforms, "we have to rule out all possible other non-biological means of producing it".

Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate, which has conducted several fly-bys of Venus, called Monday's research "intriguing".

He added that the planet was the focus of two out of four of NASA's next four candidate missions under its Discovery Program, as well as Europe's proposed EnVision mission, in which NASA is a partner.

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 our home planet 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