Leonard David's INSIDE OUTER SPACE

As seen in the ultraviolet, Venus image taken by NASA’s Pioneer-Venus Orbiter in 1979.
Credit: NASA

The clouds of Venus are potentially amenable to the growth of microorganisms.

A new study points to photosynthesis that might occur around-the-clock in Venus’ clouds with the middle and lower clouds receiving similar solar energy as Earth’s surface.

Researchers report that photosynthesis may continue through the night due to thermal or infrared energy originating from the surface and the atmosphere. 

Credit: Rakesh Mogul, et al.

The study, “Potential for Phototrophy in Venus’ Clouds,” was led by Rakesh Mogul, professor of Biological Chemistry at Cal Poly Pomona. It was published online this week as part of an October 2021 special collection of the journal Astrobiology focused on the possible suitability of Venus’ clouds for microbial life, and the constraints that may prohibit life.

Acceptable range

“Our study provides tangible support for the potential for phototrophy and/or chemotrophy by microorganisms in Venus’ clouds,” said Mogul in a university release. 

“The acidity and water activity levels potentially fall within an acceptable range for microbial growth on Earth, while the constant illumination with limited UV suggests that Venus’ clouds could be hospitable for life,” Mogul explains. “We argue that Venus’ clouds, therefore, make a great target for habitability or life detection missions, like those currently planned for Mars and Europa.”

The study also found that after filtering through the Venusian atmosphere, sunlight gets scrubbed of much of the ultraviolet radiation (UV), which is harmful to life, as result of scattering and absorption, providing a benefit like Earth’s ozone layer.

Credit: Rakesh Mogul, et al.

Chemical conditions

Mogul and his team, using new interpretations to refractive index and radio occultation measurements obtained from Venus’ clouds, found that the chemical conditions of Venus’ clouds are potentially hospitable to microorganisms.

“We show that solar irradiances calculated across Venus’ clouds support the potential for Earth-like phototrophy and that treatment of Venus’ aerosols containing neutralized sulfuric acid favor a habitable zone,” the paper explains.

With a targeted launch for fiscal year 2030, NASA’s DAVINCI+ will send a probe to brave the high temperatures and pressures near Venus’ surface to explore the atmosphere from above the clouds to near the surface. During the final leg of its free-fall descent, the probe will capture images and chemistry measurements of the deepest atmosphere on Venus for the first time.
Credits: NASA GSFC visualization by CI Labs Michael Lentz and others

Upcoming missions

Given the set of Venus probes now on the books from NASA, Europe and perhaps Russia, could they help further life detection on that cloud-veiled world?

“The upcoming mass spectral experiments on DAVINCI could really help in detailing the chemical makeup of the clouds; which by inference could tell us more about the habitability-related parameters of acidity, water activity, and etc.,” Mogul told Inside Outer Space. “I think many of the future plans are still in flux, though I believe Rocket Lab is also discussing spectral measures to get chemical information regarding cloud composition. As for life detection at Venus, we’re probably a long ways away!”

The co-authors of the study are Sanjay S. Limaye (University of Wisconsin, Madison), Yeon Joo Lee (Technische Universitat Berlin, Berlin, Germany) and Michael J. Pasillas (Cal Poly Pomona).

To take a look at the paper — “Potential for Phototrophy in Venus’ Clouds” — go to:

https://www.liebertpub.com/doi/full/10.1089/ast.2021.0032

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