Sources such as volcanoes,meteorites or lightning couldn’t account for it. “They were orders of magnitude off,” said Dr McKemmish.
That leaves three explanations:measurement error (Dr McKemmish’s most likely explanation);a physical process we don’t yet understand;or microbes living in the planet’s clouds.
“On Earth,phosphine is a sign of life,” said Dr McKemmish.
DAVINCI+ will fly twice past Venus,tracking the clouds and mapping the surface,before releasing a probe through the atmosphere. The probe will take samples of the gases and photograph the planet’s surface,looking for evidence of ancient oceans.
An artist’s impression of DAVINCI+’s mission.Credit:NASA GSFC visualization and CI Labs Michael Lentz and colleagues
VERITAS will orbit the planet and use radar to map Venus’ surface,looking for the chemical fingerprints of dried water and signs of plate tectonics.
In a single year,the Earth’s continents move a few centimetres. But over hundreds of millions of years,the entire surface of the Earth is recycled down into the red-hot mantle beneath the crust and new nutrient-rich land is created via volcanoes.
Without that renewal,the nutrients and minerals of the Earth’s surface would soon be depleted.
Louis Moresi,a professor of geodynamics at the Australian National University,said:“It’s like turning the soil over. The Earth is the only place we know it happens,and it’s the only place we know that there is life.”
DAVINCI+ will drop a probe into Venus’ atmosphere.Credit:NASA GSFC visualization and CI Labs Michael Lentz and colleagues
Venus does not appear to have plate tectonics in the classic sense. But its surface is not old and weathered like that of the moon or Mars,and there are tantalising hints of mountains on the surface – signs of movement.
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It is possible the surface is being rapidly weathered and turned over by the planet’s atmosphere,or another process we still don’t understand.
If it has its own form of plate tectonics,that will offer important clues for which planets circling other stars might be able to support life,said Professor Moresi.
“Venus is our best bet to answer that question,” he said.