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When scientists last September claimed to have discovered phosphine in the clouds of Venus – a compound that on Earth is produced by either industry or microbes – it sparked huge debate about whether this was a sign of potential life on Earth's neighbouring planet. Though doubts over the Venus claims have since emerged, the idea of life in the clouds of other planets prompted .

Though science fiction writers have written of cloud-based extraterrestrials in novels such as Iain M Banks' The Algebraist, clouds have not generally been a primary target for astrobiological searches: large bodies of liquid water on or below a planetary surface have been regarded as a better hunting ground. However, active life can exist in clouds, as demonstrated by diverse and active microbial communities that inhabit the clouds above us on Earth.

Dr Marcus Dymond

Jupiter clouds (WikiImages via Pixabay)

With the Venus claims sparking renewed interest in extraterrestrial clouds as possible havens of life, the study, led by Dr John Hallsworth at Queens University Belfast, analysed data obtained from the atmosphere of Venus and other planets to determine their water activity, based on the mantra for life of “follow the water”.

, a Principal Lecturer in School of Pharmacy and Biomolecular Sciences, said: “A critical measure of the limits of life on Earth is called the water-activity - put simply it’s the effective concentration of water in a mixture – Venus’s clouds are too dry to be habitable. My research focuses on lipid membranes, a protective barrier that surrounds all known life-forms, and the paper also shows that the molecules we think of as important for life on Earth - proteins, lipids and DNA - are unlikely to be stable at the concentrations of sulphuric acid in Venusian sulphuric acid clouds.

“But the work also sets out a technique for determining the permissiveness of other planetary atmospheres for Earth-like life. Using entry probe data from other planetary atmospheres, this showed Jupiter’s atmosphere has water activity values that would be permissive for life, as we know it. That’s not to say that there is life on Jupiter - but this approach suggests it might be a good place to look.”

The techniques outlined in the Nature paper can also be applied to planets orbiting other stars (exoplanets) as new telescopes are developed that provide details of the temperature, pressure, and water abundance in their atmospheres.