There are different objects in the solar system – planets and their moons, comets and asteroids. The number of the latter, according to estimates, may reach about one million. It has been orbiting the Sun for billions of years, and until now it was thought that the water on it, if it existed at all, should have evaporated long ago. However, new research using data from the SOFIA observatory has shown the presence of water on the asteroids Eris and Massalia.
The description and results of the research were published in “The Planetary Science Journal” (DOI: 10.3847/PSJ/ad18b8).
Sofia
SOFIA (Stratospheric Observatory for Infrared Astronomy) will be decommissioned in 2022. It was an aircraft-mounted telescope. The observations were made at an altitude of more than 12,000 metres, because at low altitudes, water vapor absorbs infrared radiation, and SOFIA worked in this radiation range.
Using data collected by the observatory, scientists looked at four silicate-rich asteroids. SOFIA's FORCAST instrument helped isolate mid-infrared spectral signatures indicating the presence of molecular water in two of them.
Water on asteroids
“Asteroids are remnants of planetary formation, so their composition varies depending on where they formed in the solar nebula,” said Dr. Anicia Arredondo from the Southwest Research Institute (SwRI), lead author of the study. “The distribution of water on asteroids is particularly interesting because it may shed more light on how water is delivered to the Earth’s surface,” she added.
Researchers believe that anhydrous, dry silicate asteroids formed near the Sun, but ice had no chance of surviving near the star. Near the Sun, ice-free siliciclastic asteroids dominate, while icy bodies are more common further away. Understanding the location and composition of asteroids will allow us to know how materials in the solar nebula were distributed, even before the formation of planets and asteroids, and how they have evolved since their formation.
The distribution of water in the solar system may also give an idea of what the distribution of water in other planetary systems might be like, and since water is essential for life on Earth, it may also indicate where to look for potential life, both in our solar system and beyond.
– We discovered a feature clearly attributed to molecular water on asteroids Eris and Massalia. We built our research on the team's success in detecting molecular water on the moon's sunlit surface. “We thought we could use SOFIA to find this spectral signature on other objects,” Arredondo said. The success reported by the scientist confirms that water on the Silver Globe is more common than previously thought and can be found even on the sunlit surface of our natural satellite (more about this in the text: NASA confirms the presence of water in sunlit areas on the moon).
Iris and massalia
The diameter of the iris is about 199 km. It orbits in the asteroid belt outside the orbit of Mars and takes 3.7 years to complete one orbit around the Sun. Massalia is slightly smaller. Its diameter is about 135 km, and it has a similar orbit.
Two other asteroids, Parthenope and Melpomene, were also analysed, but the quality of the data for these objects made it impossible to draw definitive conclusions. If there was water on these asteroids, FORCAST's sensors were not sensitive enough to detect it.
Previous observations of asteroids have been unable to distinguish between actual water and its close chemical relative: the hydroxyl group. But in new analyses, researchers have addressed this issue. According to them, every cubic meter of regolith found on the asteroid contains about 350 milliliters of water. This result is similar to the value estimated for lunar regolith in a 2020 study using data collected by the SOFIA observatory.
Arredondo noted that water on asteroids may be bound to minerals. The researcher noted that it could also be adsorbed on silicates and be trapped or dissolved in antisilicate glass.
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