Airborne dust could be indicator of habitable planets

An artist's impression of an exoplanet Credit: PA Images

The hunt for habitable planets could be boosted by looking for dust - that's according to new research from scientists at a Norfolk university.

Over the last few years astronomers have found many new planets which could be capable of supporting life.

UPI 20180416 was discovered in 2018 and is one of sixteen super-Earths discovered by the European Southern Observatory.

And earlier this year an exoplanet more than double the size of Earth, which was deemed potentially be habitable, was discovered by Cambridge astronomers.

Now researchers at the UEA in Norwich have fond that the presence of airborne dust could signify the increased habitability of distant planets.

Researchers suggest that planets with significant airborne dust – similar to the world portrayed in the classic sci-fi Dune – could be habitable over a greater range of distances from their parent star, therefore increasing the window for planets capable of sustaining life.

Kyle MacLachlan as Paul Atreides in David Lynch’s film Dune Credit: Universal

The research team - which also included the University of Exeter and the Met Office - found three primary impacts of dust.

Planets orbiting close to stars smaller and cooler than the Sun, so-called M—dwarfs, are likely to exist in synchronised rotation-orbit states, resulting in permanent day and night sides.

The researchers found that dust cools down the hotter dayside but also warms the night side, effectively widening the planet’s `habitable zone’, the range of distances from the star where surface water could exist. Detection and characterisation of potentially habitable distant planets is currently most effective for these types of worlds.

The University of East Anglia in Norwich Credit: ITV News Anglia

The results, published today in Nature Communications, also show for planets in general, cooling by airborne dust could play a significant role at the inner edge of this habitable zone, where it gets so hot that planets might lose their surface water and become inhabitable - in a scenario thought to have occurred on Venus.

As water is lost from the planet and its oceans shrink, the amount of dust in the atmosphere can increase and, as a result, cool the planet down. This process is a so-called negative climate feedback, postponing the planet’s loss of its water.

Prof Manoj Joshi from UEA said that this study shows how the possibility of exoplanets supporting life depends not only on proximity to a sun-like star - but also on the planet’s atmospheric make-up.

“Airborne dust is something that might keep planets habitable, but also obscures our ability to find signs of life on these planets. These effects need to be considered in future research.”

Prof Manoj Joshi

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. But these ‘synchronised orbit’ planets are very different. 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.”

Dr Ian Boutle

The quest to identify habitable planets far beyond our solar system is an integral part of current and future space missions, many focused on answering the question of whether we are alone.