For decades, scientists engaged in the search for life in the Universe (aka. astrobiology) have focused on searching for life on other Earth-like planets. These included terrestrial (aka. rocky) planets beyond our Solar System (extrasolar planets) and ones here at home. Beyond Earth, Mars is considered to be the most habitable planet next to Earth, and scientists have also theorized that life could exist (in microbial form) in the cloud tops of Venus.
In all cases, a major focal point is whether or not planets have large bodies of water on their surfaces (or did in the past). However, a new study led by a research team from the UK and German (with support from NASA) has shown that the existence of life may have less to do with the quantity of water and more to with the presence of atmospheric water molecules. As a result, we may have better luck finding life on Jupiter’s turbulent cloud deck than Venus’.
The study that describes their findings, which was recently published in Nature Astronomy under the title “Water activity in Venus’s uninhabitable clouds and other planetary atmospheres,” was led by Dr. John E. Hallsworth of the School of Biological Sciences at Queen’s University Belfast. He was joined by colleagues from multiple universities in the UK and Germany, and the NASA Ames Research Center’s Space Science Division (SSD).
This artistic impression depicts Venus. Astronomers at MIT, Cardiff University, and elsewhere may have observed signs of life in the atmosphere of Venus. Credits: ESO (European Space Organization)/M. Kornmesser & NASA/JPL/Caltech
Venus has been the focal point of a lot of interest lately, ever since the announcement that phosphine gas had been detected in the planet’s dense atmosphere. These findings, according to a team of independent researchers, was a possible sign that microbial life might exist in Venus’ sulfuric acid clouds (aka. a potential biosignature). However, according to this latest study, Venus’ atmosphere doesn’t have enough water activity to support this claim.
This conclusion is based on a new method devised by Hallsworth and his colleagues to determine the leve of water activity in a planet’s atmospheres. They then applied this method on Venus’ atmosphere, where temperatures range from 30 to 80 °C (86 to 176 °F) at altitudes of 50 km (30 mi) above the surface and water vapor accounts for about 0.002% of the atmosphere by volume.
Ultimately, the researchers found that the water activity in Venus’ atmosphere was over one hundred times beneath the lower limit. When they applied this same method to Jupiter’s clouds, they found something else entirely. Above the stratosphere-thermosphere boundary (320 km above the troposhere) there is a “sweet spot” where temperatures are stable and the clouds have a high enough concentration of water vapor.
In short, the clouds of Venus do not have what it takes to support life, but Jupiter’s upper atmosphere does. This information is highly significant at a time when NASA and other space agencies are proposing various astrobiology missions for the near future. Before these missions can be sent out to search for life, it’s imperative that we prioritize destinations based on the likelihood of scientific returns.
NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill (wikimedia commons)
As Dr. Hallsworth explained in a Queen’s University Belfast news release:
“Our research shows
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