Scientists have discovered, for the first time, water molecules on the surface of an asteroid.

The team from Southwest Research Institute (SwRI) in the US looked at four silicate-rich asteroids using the FORCAST instrument from the retired Stratospheric Observatory for Infrared Astronomy (SOFIA) to isolate the mid-infrared spectral signatures indicative of molecular water on two of them. SOFIA is a joint project of NASA and the German Space Agency.

“Asteroids are leftovers from the planetary formation process, so their compositions vary depending on where they formed in the solar nebula,” said lead author Anicia Arredondo, from the SwRI.