Planetary science: Mineral dust may increase habitability of exoplanets

Atmospheric mineral dust may increase the potential habitability of exoplanets suggests a study this week in Nature Communications. The findings highlight the need to consider the potential effects of dust when studying terrestrial exoplanets.

The so-called ‘habitable zone’ is the region around a star where an Earth-like planet may host liquid water at its surface. As such, it is a preferred target when searching for extra-terrestrial life. However, habitability can also depend on the makeup of the planetary atmosphere. Mineral dust (carbon-silicate material from the surface) can have an effect on the climate system, but this has been neglected in modelling the climate of exoplanets until now.

Ian Boutle and colleagues show, via simulations, how airborne mineral dust can have a significant impact on the habitability of Earth-like exoplanets. The authors found that on tidally locked planets (where the same side of the planet always faces the star), dust cools the day-side of the exoplanet and warms the night-side, therefore widening the habitable zone for such planets to exist in. They suggest that dust can slow down a planet’s water loss at the inner edge of the habitable zone and warm planets at the outer edge.

In simulations of transmission spectra from exoplanets, the authors also found that the inclusion of dust can obscure the presence of key biomarkers, such as water vapour and oxygen. They argue that this should be taken into consideration when interpreting observations about the habitability of exoplanets.