Water molecules have been detected on the surface of asteroids for the first time, proving that these remnants from the formation of our solar system are not just anhydrous space rocks.

Astronomers believe that the impact of asteroids falling on our planet may have helped transport water and other elements to the early Earth, so finding water elements in asteroids could support this theory, according to a new study.

The data were collected by an instrument on the Stratospheric Observatory for Infrared Astronomy airborne telescope. The infrared telescope, named SOFIA, flew aboard a Boeing 747SP aircraft modified to fly through the stratosphere over 99% of Earth’s atmosphere, which blocks infrared light.

The Faint Object Infrared Camera for the SOFIA telescope, or FORCAST instrument, allowed astronomers to detect water molecules in Iris and Marseilles, two asteroids in the main asteroid belt between the orbits of Mars and Jupiter. Both are more than 223.1 million miles from the sun.

The findings were published Monday in The Planetary Science Journal.

Astronomers decided to use SOFIA to study asteroids after the telescope detected evidence of water on the moon, said study lead author Dr. Anisia Arredondo, a researcher at the Southwest Research Institute in San Antonio.

Evidence of hydration had been found in the two asteroids in the past by the study’s other author Dr. Maggie McAdam, a researcher at NASA’s Ames Research Center in Mountain View, California, while using a different telescope. But the researchers weren’t sure whether water or another molecular compound such as hydroxyl caused the hydration, Arredondo said.

“Our new observations with SOFIA showed conclusively that what they saw was indeed water,” Arredondo said. “But these objects are part of the S class of asteroids, which means they are mostly silicates, and until Dr McAdam’s results, they were thought to be completely dry.”

Finding water on dry cosmic surfaces

The amount of water the team found was roughly equivalent to that of a 12-ounce bottle of water trapped in a cubic yard of soil, Arredondo said. The telescope detected water molecules in one of the largest craters on the Moon’s southern hemisphere in 2020.

Like the water found on the lunar surface, “in asteroids, water can also be bound to minerals as well as adsorbed on silicate and trapped or dissolved in silicate impact glass,” Arredondo said.
Asteroids are the leftovers from when the planets formed in our solar system. Studying their compositions can tell astronomers where the asteroids in our cosmic neighborhood came from.

Searching for water throughout the solar system

The researchers tried to look for water in two other asteroids using SOFIA, but the detection was too faint. Now, the team is using the James Webb Space Telescope to shed asteroids and look for evidence of water.

While Webb’s observations continue, Arredondo said the preliminary results have encouraged the team to request time to observe 30 more asteroids using the powerful infrared telescope.

“The JWST telescope is much larger than the SOFIA telescope, so it can collect data with higher quality and it can collect data on more asteroids in a shorter period of time,” Arredondo said. “I hope to be able to observe many different asteroids with JWST to look for evidence of water.