Are we alone? Astronomers propose looking for mineral dust on exoplanets to answer the question

Mineral dust — comprising carbon-silicate material lifted from the planet's surface — may influence climatic conditions on a planet, thereby making it more hospitable

                            Are we alone? Astronomers propose looking for mineral dust on exoplanets to answer the question
(Denis Sergeev/ University of Exeter)

Alien life hunters should consider looking at exoplanets with mineral dust circulating in the atmosphere, propose scientists in a new study. These distant lands with potential for life may look strikingly similar to the one depicted in a sci-fiction classic named 'Dune'.

The mineral or airborne dust — comprising carbon-silicate material rising from the planet's surface — may influence the climatic conditions on a planet, thereby making it more hospitable. In other words, it would regulate temperatures, while also preventing the loss of water from the planet, according to researchers. A distant land is labeled habitable if its conditions keep surface water from freezing and evaporating.

Exoplanets capable of hosting life depends on not only on the amount of light energy it draws from the nearest star but also on the atmospheric make-up. "Airborne dust is something that might keep planets habitable," Dr Manoj Joshi from the University of East Anglia (UEA), who was involved in the study, said in a statement. The study suggests planets with airborne dust may support life even at great distances from their parent star. 

However, dust could hide a key piece of evidence for life: methane. It may indicate the presence of microbes, as about 90-95% of the gas has a biological origin on Earth. The experts suggest that astronomers must carefully evaluate exoplanets for their habitability before rejecting them. In this study, researchers from the University of Exter and UEA modeled conditions in terrestrial or Earth-sized exoplanets using climate models. They looked at M dwarfs, stars which are smaller and cooler than the Sun. Planets that orbit them have permanent day and night sides, which means only one part of the planet faces the star.

(Getty Images)

Their analysis showed that dust plays a dual role: it cools down temperatures in regions facing the M dwarfs and warms up the other end, which is perpetually dark. "Here, the dark sides of these planets are in perpetual night, and the warming effect wins out, whereas, on the dayside, the cooling effect wins out. The effect is to moderate the temperature extremes, thus making the planet more habitable," Boutle added.

Dust regulates temperatures on the Earth and Mars — albeit differently. Dr Ian Boutle, lead author of the study and jointly from the Met Office and the University of Exeter said: "On Earth and Mars, dust storms have both cooling and warming effects on the surface, with the cooling effect typically winning out." Besides, dust also has a role in maintaining water on the surface. High temperatures are not conducive to life as they speed up evaporation. Venus is a case in point. But mineral dust brings down temperatures, preventing the loss of water.

Nathan Mayne, from the University of Exeter, who along with a co-author was able to work on this project thanks to funding from the Science and Technology Facilities Council (STFC) added: "Research such as this is only possible by crossing disciplines and combing the excellent understanding and techniques developed to study our own planet's climate, with cutting edge astrophysics." The results are published in Nature Communications.

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