Life on Venus could be hiding in its strange clouds
A team of scientists modeling the Venusian atmosphere have found data that could help explain the puzzling chemistry of the planet’s clouds. The findings reinforce the possibility that life exists in Venus’ atmosphere, a still controversial idea that will be investigated by several planned missions to the scorching planet.
Venus is the second planet from the Sun, which makes it much hotter than Earth. Besides the warmth of the planet, Venus is a barren, rocky wasteland dominated by volcanoes and clouds of toxic sulfuric acid. This cloud layer – about 19 km thick – covers the planet’s surface for Earth-based observers most of the time, and recently it has been in the spotlight as a possible hiding place for alien life.
Recent research has modeled these clouds more deeply, and scientists have found that the planet’s clouds are not entirely composed of sulfuric acid but contain a certain amount of mixed ammonium salt sludge. The team’s study was published in the Proceedings of the National Academy of Sciences.
“Our model predicts that clouds are not made entirely of concentrated sulfuric acid, but that cloud droplets are partially neutralized. Our model postulates that the compound that neutralizes acid in clouds is ammonia, ”Janusz Petkowski, an MIT astrobiologist and co-author of the recent study, said in an email. “The source of ammonia is unknown, but could be the result of the biological production of ammonia in cloud droplets. Due to the neutralization of acid, clouds are not more acidic than some extreme terrestrial environments that harbor life.
The recent work builds on high-profile research published last year in Nature, which claimed to detect phosphine gas in the Venusian atmosphere. (The scientists behind the new article were also among the authors of the article on phosphine.) Phosphine is produced by microorganisms that do not need oxygen to survive, so the presence of the gas was a surprising and exciting sign that something biological could be happening in those clouds. The conclusion was controversial; other researchers said the supposed signal from phosphine was actually just sulfur dioxide, while others suggested that active volcanoes, not life, could be responsible for it.
“To our knowledge, no life could survive in the droplets of Venus,” Sara Seager, an MIT planetologist and co-author of the new study, said in a statement from the institute. “But the point is, maybe some life is out there and changing its surroundings to be habitable.”
The new article did not focus on phosphine but rather on some unexplained chemical signatures in the clouds of Venus. Years of observations have indicated more water vapor and sulfur dioxide than expected. Ammonia, the researchers thought, could explain these anomalies.
“Ammonia shouldn’t be on Venus,” Seager added. “There is hydrogen attached to it, and there is very little hydrogen around. Any gas that does not belong to the context of its environment is automatically suspected of being manufactured by life.
The models indicated that if microorganisms were on Venus and produced ammonia, oxygen would be released as a byproduct. Additionally, ammonia (which is basic) would neutralize sulfuric acid droplets in clouds, making them somewhat habitable. While all of this work has been done with models, future space probe missions could help us get answers to what is really going on in the clouds.
These missions are NASA’s VERITAS and DAVINCI + missions, ESA’s EnVision Orbiter, and (possibly) the privately-offered and funded Venus Life Finder missions Seager and Petkowski are working on. The latter is the only one whose fundamental goal is to study the possibility of extraterrestrial life on Venus, but space agency missions will likely glean information on the matter as well. Of these three missions, DAVINCI + is the only mission that will actually enter the atmosphere of Venus and sample it as the spacecraft descends to the surface of the planet.
If life of any kind were discovered off Earth – whether fossilized on the surface of Mars, thriving in the clouds of Venus, or swimming in the ocean of a frozen moon – it would be one of the most important scientific discoveries of all time. But there is a long and uncertain road before such claims can be made.
More: The 7 Weirdest Things About Venus, Hell Planet