Scientists have identified water molecules on two supposedly "dry" main-belt asteroids, 7 Iris and 20 Massalia, utilizing data from a now-retired airborne telescope. This discovery marks the first time water has been detected on these asteroids, challenging previous assumptions about their composition.
Lead author of the study, Anicia Arredondo, a prominent asteroid researcher at the Southwest Research Institute, expressed the significance of the finding. "We detected a feature that is unambiguously attributed to molecular water on the asteroids," she stated in a press release accompanying the publication of the paper in The Planetary Science Journal.
The asteroids under scrutiny primarily consist of silicates, leading scientists to believe they lacked water due to their formation proximity to the Sun, where water ice condensation was deemed improbable. Instead, water was expected to be prevalent on asteroids formed farther from the Sun. However, the discovery of water molecules on Iris and Massalia challenges these assumptions. Scientists propose that the water may be dissolved in silicate glass resulting from impacts, trapped within surface silicates, or chemically bonded to other minerals on the asteroids.
This breakthrough has significant implications for our understanding of water distribution across the asteroid population and its role in celestial bodies' formation. Arredondo highlighted the importance of unraveling this mystery, stating that it could provide insights into the origins of water on Earth.
The detection of water was made possible through instruments like the Stratospheric Observatory for Infrared Astronomy (SOFIA) and its FORCAST instrument, capable of capturing unique infrared signatures indicative of water molecules. Notably, SOFIA had previously detected water in the Moon's southern hemisphere, demonstrating its efficacy in celestial water detection.
By analyzing data from four asteroids, including 11 Parthenope and 18 Melpomene, the research team observed absorption features consistent with water on Iris, Massalia, and Melpomene. However, Iris and Massalia exhibited additional absorption signatures specifically attributable to water, strengthening the case for water presence on these asteroids.
Looking ahead, scientists anticipate that advanced technologies such as the James Webb Space Telescope (JWST) could further illuminate the presence of water on other asteroids. The research team has already conducted observations on two additional asteroids using JWST and aims to expand their investigations to 30 more objects. Through continued observations, they hope to gain a comprehensive understanding of water distribution across the solar system, unlocking further mysteries of celestial bodies.
