A new study from an international team of scientists proposes that microbial life could exist in the clouds of Venus. The exciting hypothesis suggests mysterious dark patches seen in the atmosphere could be something akin to algae blooms seen in oceans on Earth.

The surface of Venus is infamously inhospitable. Dominated by volcanos, plains of lava, and temperatures above 450° C (860° F), the landscape is hellish and not that likely to be able to sustain life. Up in the clouds, on the other hand, scientists have identified a sweet spot of environmental conditions that may just be able to support microbial life.

Around 30 miles (48 km) above the planet's surface is a lower cloud layer with temperatures around 60° C (140° F) and pressures similar to that of Earth (unlike the planet's surface with a pressure of 90 atmospheres, equivalent to the pressure felt over a half a mile beneath the ocean). It's not impossible to think that microbial life could exist in this atmospheric Goldilocks zone, after all, here on Earth microorganisms have been found alive at altitudes as high as 25 miles (41 km).

In addition to these incredibly suitable environmental conditions, it's a strange and inexplicable atmospheric phenomenon that is really driving the hypothesis. As long as we have had telescopes good enough to observe Venus in detail, we have witnessed mysterious dark patches moving through its atmosphere. These dark patches seem to be composed of sulfuric acid, alongside unknown particles that absorb ultraviolet light.

"Venus shows some episodic dark, sulfuric rich patches, with contrasts up to 30–40 percent in the ultraviolet, and muted in longer wavelengths," says planetary scientist Sanjay Limaye. "These patches persist for days, changing their shape and contrasts continuously and appear to be scale dependent."

Limaye was struck by the potential similarities between these strange unidentified atmospheric particles and bacteria on Earth that have similar light-absorbing properties. The scientists note in the paper that similar bacterial life on Earth can feed on carbon dioxide and produce sulfuric acid, another primary element observed in these strange Venusian clouds.

This isn't the first time that this hypothesis has been proposed, but the team's paper is undoubtedly the most comprehensive examination of this intriguing idea. The next step, of course, is to prove the hypothesis. Limaye points to an unmanned aerial vehicle (UAV) concept from aerospace company Northrop Grumman as an exciting possibility. Called VAMP (Venus Atmospheric Maneuverable Platform), this giant UAV could potentially stay aloft in the Venusian clouds for 12 months, constantly gathering data and samples.

The only Venus mission currently on the cards that something like VAMP could be attached to is the Venera-D proposal from Russia. The ambitious plan, hopefully launching within the next 10 years, involves both an orbiter and a lander. At one point, Russia did approach NASA regarding potentially collaborative activities on the mission, but there has been no official confirmation of the collaboration moving forward at this point in time.

Despite attention in recent years moving to moons like Europa and Titan, Venus still holds many compelling mysteries and this new paper suggests the first extraterrestrial microbial life could be found in this fascinating planet's strange clouds.

The article was published in the journal Astrobiology.

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