Scientists from the Southwest Research Institute have for the first time detected water molecules on the surface of asteroids. The discovery was reported in a paper published in The Planetary Science Journal.

Astronomers studied four silicate-rich asteroids - Iris, Parthenope, Melpomene, and Massalia. The observations were made using the FORCAST mid-infrared camera instrument on the SOFIA Stratospheric Observatory. On three asteroids (Iris, Melpomene, and Massalia) an absorption line of 3 micrometers was found, indicating the simultaneous presence of oxygen and hydrogen atoms. The 6-micrometer absorption line indicates the presence of water on Iris and Massalia.

Anhydrous silicate asteroids are known to form near the Sun, and icy, water-rich materials coalesce in the outer Solar System. Knowing the location of asteroids with a specific chemical composition helps determine how materials were distributed in the protosolar nebula. Rocky S-class asteroids were previously thought to be waterless, and the 6-μm spectral feature had never been detected on these celestial bodies.

Previously, SOFIA detected water molecules in one of the largest craters in the southern hemisphere of the Moon. A cubic meter of regolith was found to contain chemically bound water weighing approximately 340 grams. About the same amount of water has been observed on asteroids.

Scientists plan to get more data on asteroids Parthenope and Melpomene using the James Webb Space Telescope, as well as survey 30 more targets. /BGNES