An international team of astronomers Monday announced the discovery of a rare gas molecule - phosphine - in the clouds of Venus, which may be the first solid evidence of extraterrestrial life in the solar system.
The researchers say on Earth, phosphine is only made industrially or by microbes that thrive in oxygen-free environments. The international team, which includes researchers from Britain, the U.S. and Japan, published their findings in two papers - the science journal Nature on Monday, and Astrobiology journal on Saturday.
Phosphine was first spotted in observations that were made by Cardiff University astronomer Jane Greaves using the James Clerk Maxwell Telescope (JCMT) in Hawaii. The discovery was then confirmed using a more sensitive radio telescope, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.
The team estimates that phosphine exists in Venus' clouds at a small concentration, only about 20 molecules in every billion. Still, after running several calculations, they determined there were no non-biological sources on the planet that could account for the levels of phosphine they discovered in the atmosphere.
Astronomers have speculated for decades that high clouds on Venus could offer a home for microbes - floating free of the scorching surface but needing to tolerate very high acidity. They say detection of phosphine could point to such extra-terrestrial "aerial" life.
Another member of the team, Massachusetts Institute of Technology molecular astrophysicist Clara Sousa Silva, has investigated phosphine as a "biosignature" gas of non-oxygen-using life on planets around other stars. She said finding it on Venus is exciting and extraordinary.
But she said it raises many questions regarding how any organisms, if they exist, could survive in the planet's atmosphere, where clouds are made up of about 90% sulphuric acid. So, team members acknowledge that confirming the presence of "life" needs a lot more work.