Traces of water discovered on the surface of asteroids for the first time

Astronomers believe that asteroid impacts with our planet may have helped bring water and other elements to the early Earth, so finding evidence of water on asteroids could support this theory, according to a new study.

According to CNN, the data was collected using an instrument mounted on the now-retired airborne telescope of the Stratospheric Observatory for Infrared Astronomy. The infrared telescope, called SOFIA, was aboard a Boeing 747SP aircraft modified to fly through the stratosphere, above 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 on Iris and Massalia, 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 results were published Monday in the journal Planetary Science.

Astronomers were inspired to use SOFIA to study asteroids after the telescope found evidence of water on the Moon, said lead study author Dr. Anicia Arredondo, a postdoctoral fellow at the Southwest Research Institute in San Antonio.

Evidence of hydration was discovered on two asteroids earlier by study co-author Dr. Maggie McAdam, a research scientist at NASA’s Ames Research Center in Mountain View, California, using a different telescope. But the researchers weren’t sure whether it was water or another molecular compound, such as hydroxyl, that was causing the hydration, Arredondo notes.

“Our new observations from SOFIA definitively confirmed that what they were seeing was indeed water,” says Arredondo. “But these objects are classified as S-class asteroids, which means they are mostly silicates, and up until Dr. McAdam’s results, they were assumed to be completely dry.”

The amount of water the team found was roughly equivalent to the amount of a 12-ounce bottle of water contained in a cubic meter of soil, Arredondo said, which is comparable to SOFIA’s find on the Moon. The telescope recorded the presence of water molecules in one of the largest craters in the southern hemisphere of the Moon in 2020.

Like water found on the lunar surface, “on asteroids, water can also bind to minerals and also adsorb to silicates and be trapped or dissolved in silicate impact glass,” Arredondo says.

Asteroids are remnants of the time when planets formed in our solar system. Studying their composition can tell astronomers where asteroids originated in our cosmic environment, CNN explains.

“When the solar system formed, different materials formed depending on their distance from the Sun, because material (further away) from the Sun cooled faster (than) material closer to the Sun,” Arredondo notes. “This is why the inner planets, such as Earth and Mars, are made of rock, while the outer planets, such as Neptune and Uranus, are made of ice and gas.”

The discovery of water on Iris and Massalia could help astronomers trace the history of these particular asteroids, suggesting that their formation occurred far enough from the Sun to avoid the water boiling away due to high temperatures.

Researchers tried to find water on two other asteroids using SOFIA, but the detection was too weak. The team is now using the James Webb Space Telescope to observe various asteroids and look for signs of water.

While Webb’s observations continue, Arredondo says the preliminary results have prompted the team to request time to observe 30 more asteroids with 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,” explains Dr. Arredondo. “I hope to be able to observe many different asteroids with JWST to look for that signature of water, and hopefully be able to take an inventory of water in the asteroid belt.”

The Webb telescope could help astronomers better understand the distribution of water throughout the solar system, as well as the composition of different types of asteroids.

“We really didn’t expect to find water on these silicate-rich asteroids,” admits Arredondo. “Basically, when we talk about hydration on asteroids, we’re talking about carbon-rich asteroids like asteroid Bennu, which NASA’s OSIRIS-REx mission went to. So now I want to look at the trends between (amount of) hydration and composition. I want to know whether carbon-rich asteroids contain significantly more water than silicate-rich asteroids, or whether they have the same amount.”