Using data from the Stratospheric Observatory for Infrared Astronomy (SOFIA) – a joint project of NASA and the German space agency DLR – scientists from the Southwest Research Institute have for the first time detected water molecules on the surface of asteroids. Scientists studied four silicate-rich asteroids with the FORCAST instrument and identified two spectral signatures in the mid-infrared range, indicating the presence of molecular water.

“Asteroids are remnants of planet-forming processes, so their composition depends on where they formed in the solar nebula,” said SwRI’s Dr. Anisia Arredondo, lead author of a paper on the discovery in the Planetary Science Journal. “The distribution of water on asteroids is of particular interest because it may shed light on how water was delivered to Earth.”

Dry silicate asteroids form near the Sun, while icy materials accumulate at great distances from the star. Understanding the location of asteroids and their composition allows us to understand how the materials in the solar nebula have been distributed and evolved since its formation. The distribution of water in our solar system will allow us to understand the distribution of water in other solar systems and, since water is essential for life on Earth, to determine where to look for potential life, both in our solar system and beyond.

“We discovered a feature on the asteroids Iris and Massalia that can definitely be attributed to molecular water,” says Arredondo. “Our research was based on the success of the team that discovered molecular water on the moon’s sunlit surface. We thought we could use SOFIA to look for this spectral signature on other bodies.”

SOFIA detected water molecules in one of the largest craters in the southern hemisphere of the Moon. Previous observations of the Moon and asteroids revealed the presence of hydrogen in one form or another, but failed to distinguish water from its close chemical relative, hydroxyl. Scientists have found in a cubic meter of soil scattered on the lunar surface, water chemically bound to minerals, roughly equivalent to a 12-ounce bottle.

“Judging by the intensity of the spectral bands, the abundance of water on the asteroid corresponds to the abundance of water on the sunlit moon,” Arredondo said. “Similarly, on asteroids, water can be bound to minerals, as well as adsorbed on silicates, trapped or dissolved in silicate shock glass.”