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While the surface conditions on Venus are known to be inhospitable, with temperatures soaring above 450 degrees Celsius, the cloudy, acidic atmosphere of the planet could potentially harbour microbial life, a new study suggests.
The research, detailed in the journal Astrobiology, supports the idea of habitability of Venus’ clouds, which was first raised in 1967 by biophysicist Harold Morowitz and astronomer Carl Sagan.
“To really know, we need to go there and sample the clouds,” said co-author of the new study Rakesh Mogul, Professor at California State Polytechnic University, Pomona.
“Venus could be an exciting new chapter in astrobiology exploration,” Mogul said.
On Earth, terrestrial microorganisms — mostly bacteria — are capable of being swept into the atmosphere, where they have been found alive at altitudes as high as 41 kilometres by scientists using specially equipped balloons, according to study co-author David Smith of NASA’s Ames Research Center.
There is also a growing catalog of microbes known to inhabit incredibly harsh environments on our planet, including the deep ocean hydrothermal vents, the toxic sludge of polluted areas, and in acidic lakes worldwide.
The study to explore habitability of Venus’ clouds led by Sanjay Limaye of the University of Wisconsin-Madison was further inspired by his visit to Tso Kar, a high-altitude salt lake in Ladakh in Jammu and Kashmir.
There he observed the powdery residue of sulfur-fixing bacteria concentrated on decaying grass at the edge of the lake being wafted into the atmosphere.
For the study, the researchers focused on unidentified particles that make up unexplained dark patches observed in the clouds of Venus.
Spectroscopic observations, particularly in the ultraviolet, show that the dark patches are composed of concentrated sulfuric acid and other unknown light-absorbing particles.
Those dark patches have been a mystery since they were first observed by ground-based telescopes nearly a century ago, Limaye said.
They were studied in more detail by subsequent probes to the planet.
The particles that make up the dark patches have almost the same dimensions as some bacteria on Earth, although the instruments that have sampled Venus’ atmosphere to date are incapable of distinguishing between materials of an organic or inorganic nature, the study said.
The patches could be something akin to the algae blooms that occur routinely in the lakes and oceans of Earth, according to Limaye and Mogul.
“Venus has had plenty of time to evolve life on its own,” explained Limaye, noting that some models suggest Venus once had a habitable climate with liquid water on its surface for as long as two billion years.
“That’s much longer than is believed to have occurred on Mars,” he added.
