Using data from the now-retired SOFIA airplane telescope, scientists think they have detected evidence of water molecules on Iris and Massalia, two well-known asteroids in the main asteroid belt.

“We detected a feature that is unambiguously attributed to molecular water on the asteroids Iris and Massalia,” Arredondo said. “We based our research on the success of the team that found molecular water on the sunlit surface of the Moon. We thought we could use SOFIA to find this spectral signature on other bodies.”

SOFIA detected water molecules in one of the largest craters in the Moon’s southern hemisphere. Previous observations of both the Moon and asteroids had detected some form of hydrogen but could not distinguish between water and its close chemical relative, hydroxyl. Scientists detected roughly equivalent to a 12-ounce bottle of water trapped in a cubic meter of soil spread across the lunar surface, chemically bound in minerals.

“Based on the band strength of the spectral features, the abundance of water on the asteroid is consistent with that of the sunlit Moon,” Arredondo said. “Similarly, on asteroids, water can also be bound to minerals as well as adsorbed to silicate and trapped or dissolved in silicate impact glass.”

You can read their paper here.

There remains uncertainty with this result, but there is also no reason for water not to be found on these main belt asteroids. They are far enough away from the Sun so that conditions are likely cold enough for that water to remain frozen or locked in the ground.