Dangerous information, life most likely can’t exist on Venus. Excellent news, it may very well be within the clouds of Jupiter

For decades, scientists engaged in the search for life in the universe (also known as astrobiology) have focused on the search for life on other Earth-like planets. This included terrestrial (also known as rocky) planets outside of our solar system (extrasolar planets) and those at home. Beyond Earth, Mars is considered to be the most habitable planet alongside Earth, and scientists have also theorized that life (in microbial form) could exist in the cloud tops of Venus.

In all cases, a major focus is on whether planets have (or have had in the past) large bodies of water on their surface. However, a new study led by a team of British and German researchers (with support from NASA) has shown that the existence of life may have less to do with the amount of water than with the presence of atmospheric water molecules. As a result, we may be luckier to find life on the turbulent cloud deck of Jupiter than on that of Venus.

The study describing their results, recently published in Nature Astronomy under the title “Water Activity in the Uninhabitable Clouds of Venus and Other Planetary Atmospheres”, was written by Dr. John E. Hallsworth of the School of Biological Sciences at Queen’s University Belfast. He was supported by colleagues from several universities in the UK and Germany as well as the Space Science Division (SSD) of the NASA Ames Research Center.

This artistic impression shows Venus. Astronomers at MIT, Cardiff University, and elsewhere may have observed signs of life in Venus’ atmosphere. Credits: ESO (European Space Agency) / M. Grain Knife & NASA / JPL / Caltech

Venus has been the focus of attention lately since the announcement that phosphine gas was discovered in the planet’s dense atmosphere. These results, according to a team of independent researchers, were a possible sign that microbial life might exist in Venus’ sulfuric acid clouds (also known as a potential biosignature). However, according to this latest study, Venus’s atmosphere does not have enough water activity to support this claim.

This conclusion is based on a new method developed by Hallsworth and colleagues to determine the level of water activity in a planet’s atmosphere. They then applied this method to the atmosphere of Venus, where temperatures range from 30 to 80 ° C (86 to 176 ° F) at altitudes of 50 km (30 miles) above the surface and where water vapor makes up about 0.002% of the atmosphere’s volume .

Ultimately, the researchers found that the water activity in Venus’ atmosphere was more than a hundred times below the lower limit. When they used the same method on the clouds of Jupiter, they found something entirely different. Above the stratosphere-thermosphere boundary (320 km above the troposphere) there is a “sweet spot” where the temperatures are stable and the clouds have a sufficiently high water vapor concentration.

In short, the clouds of Venus don’t have what it takes, but the upper atmosphere of Jupiter does. This information is of great importance 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 is imperative that we prioritize targets based on the likelihood of scientific return.

NASA / JPL-Caltech / SwRI / MSSS / Kevin M. Gill (wikimedia Commons)

Like Dr. Hallsworth stated in a press release from Queen’s University Belfast:

“Our research shows that the sulfuric acid clouds on Venus have too little water for active life to exist based on what we know about life on Earth. We also found that the water and temperature conditions in the Jupiter clouds could allow microbial life forms to persist, provided that other requirements such as nutrients are in place.

“This is a timely realization as NASA and the European Space Agency have just announced three missions to Venus in the coming years. One of them will take measurements of the Venusian atmosphere, which we can compare with our results. ”

In addition, the results of this study represent another possibility to broaden the search for habitable exoplanets. Currently, the characterization of exoplanets is focused on finding evidence of life on rocky planets with surface water. But the detection of sufficient water vapor in the atmosphere of gas giants – such as Exo-Jupiter and Exo-Neptune – could point the way to life beyond our solar system.

“We have also done calculations for Mars and Earth and show that these calculations can be done for planets outside of our solar system,” added Dr. Hallsworth added. “Although our research does not claim that extraterrestrial (microbial) life exists on other planets in our solar system, it does show that if water activity and other conditions are right, such life could exist in places we hadn’t looked for before. “

This artist’s impression shows the planet orbiting the sun-like star HD 85512 in the southern constellation Vela (The Sail). Photo credit: ESO

Dr. Christopher McKay, a planetary scientist at NASA Ames and another co-author of the study, brought his extensive expertise in planetary atmospheres and astrobiology to this research. “We infer water activity from atmospheres without any model, based only on direct observations of pressure, temperature and water concentration,” he said.

In the near future, the James Webb Space Telescope (JWST) will finally launch into space (currently planned for November 2021). With its advanced infrared imaging capabilities, the JWST will play an important role in astrobiology and the characterization of exoplanet atmospheres. Coupled with missions like the Nancy Grace Roman Space Telescope (RST), the count of potentially habitable exoplanets is expected to grow exponentially.

Dr. Philip Ball, expert on the physics and chemical biology of water and co-author of the article, said:

“The search for extraterrestrial life was sometimes a bit simplified when it came to water. As our work shows, it is not enough to say that liquid water equates to habitability. We also need to think about how earth-like organisms actually use it – which shows us that we then have to wonder how much of the water is actually available for these biological purposes. ”

Further reading: Queens University Belfast, Natural Astronomy

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