Using data from the now-retired Stratospheric Infrared Observatory (SOFIA), scientists at the Southwest Research Institute have discovered water molecules on the surface of an asteroid for the first time. The project is a collaborative effort between NASA and the German Space Agency in DLR.
The scientists used the Forcast instrument to observe four silicate-rich asteroids to isolate the mid-infrared spectral signatures on two of them, which indicate molecular water.
Asteroids are remnants of the planet-forming process, so their composition depends on where they form in the solar nebula," said Dr. Anicia Arredondo of SWRI, lead author of the discovery in the Journal of Planetary Science. "Of particular interest is the distribution of water on asteroids, as this could reveal how water is transported to Earth.
Waterless or dry silicate asteroids form closer to the Sun, while icy material condenses farther away. Understanding the location of asteroids and their composition tells us how the material in the solar nebula is distributed and how it has evolved since its formation. The distribution of water in our solar system will provide insights into the distribution of water in other solar systems and, since water is necessary for all life on Earth, will drive the search for places for potential life in and around our solar system.
We found a feature of molecular water that is clearly attributed to the asteroids Iris and Massalia," Arredondo said. "Our research is based on the success of the team that discovered molecular water on the surface illuminated by the moon's sunlight. We think we can use Sofia to find this spectral signature on other celestial bodies.
Sofia has detected water molecules in one of the largest craters in the Moon's southern hemisphere. Previous observations of the Moon and asteroids have detected some form of hydrogen, but have not been able to distinguish between water and its close relative, hydroxyl group.
Scientists have detected about the equivalent of a 12-ounce bottle of water trapped in a cubic meter of soil, distributed on the surface of the moon, chemically bound to minerals.
According to the intensity of the bands of the spectral signature, the abundance of water on the asteroid is consistent with that of the moon illuminated by sunlight," said Arredondo. "Similarly, on asteroids, water can bind to minerals or adsorb to silicates and become trapped or dissolved in silicate impact glass.
The data from the two fainter asteroids, Parthenope and Melpomene, are too noisy to draw definitive conclusions. The Forcast instrument is clearly not sensitive enough to detect water spectral signatures, if present. However, with these findings, the team is recruiting NASA's James Webb Space Telescope, a premier infrared space telescope that uses its precise optics and superior signal-to-noise ratio to study more targets.
We have already made preliminary measurements of two other asteroids with Webb in the second cycle," Arredondo said. "We have another proposal for the next cycle, which is to look at another 30 targets. These studies will increase our understanding of the distribution of water in the solar system.
References: Anicia Arredondo, Margaret M mcadam、casey i. honniball、tracy m. becker、joshua p. emery、andrew s.Rivkin, Driss Takir, and Cristina AThomas, February 12, 2024, Journal of Planetary Science.
doi： 10.3847/psj/ad18b8
Newbie Mentoring Program