Dust could hold major clue to alien life, scientists say

Planets that had been written off as uninhabitable could in fact be more likely to serve as home for life than previously thought, research indicates

Dust could represent a major clue to whether other planets are inhabitable by alien life, scientists have found.

Airborne dust on those planets appears to be a key factor in deciding the conditions on such a planet, and whether they would be right to support life.

But it could also cover up signs of life from other planets, meaning that we miss just how habitable they could be as we look around the universe in search of other worlds.

Those planets that have large amounts of such airborne dust would be habitable even when they are further from their star, the new research suggests. That in turn would mean those planets would theoretically be better as a home for life elsewhere in the universe.

The dust changes the climates of the planets so that they would be better able to deal with the extreme and critical conditions that are found throughout the universe.

The discovery suggests that planets that might have been written off as homes for life, because of their conditions, might in fact be better at supporting it than scientists had previously thought.

And the researchers behind the new paper, published in Nature Communications, urged those scouring the universe for such planets to ensure that they look for dust as a potentially key marker of whether a planet is habitable.

Many of the planets that are found as possible homes for alien life orbit stars smaller and cooler than our sun, known as M-dwarfs, and do so in "synchronised rotation-orbit states", so that it is always day on one side of the planet and night on the other. That poses a major issue for any life, since it means that each side of the planet is likely to have more extreme conditions.

However, researchers found that large amounts of airborne dust could cool the hotter side, where it is always day, as well as warming the colder night side. That means that the planet's could be more easily inhabited, since there is a wider range of distance from the star where water could exist, which is thought to be one of the key tests for life.

"On Earth and Mars, dust storms have both cooling and warming effects on the surface, with the cooling effect typically winning out. But these 'synchronised orbit' planets are very different," said Ian Boutle, lead author of the study and jointly from the Met Office and the University of Exeter.

"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."

Even on planets that have orbits like those on Earth, airborne dust could help cool any worlds that are at the inner edge of the habitable zone, where any extra heat could mean that the surface water is lost and they become uninhabitable.

The scientists, from the University of Exeter, the Met Office and the University of East Anglia, urged researchers to look for the presence of dust in the same way they search for other biomarkers that could indicate life. They also warned that the same thing keeping those worlds habitable could also stop us seeing them properly.

"Airborne dust is something that might keep planets habitable, but also obscures our ability to find signs of life on these planets," said Manoj Joshi from UEA. "These effects need to be considered in future research."

Scientists found the results by simulating Earth-sized exoplanets, using climate models that allowed them to see how naturally occuring dust would change the conditions on those worlds.