Planetary scientists using spectral data from the NASA/ESA/CSA James Webb Space Telescope have confirmed the detection of hydroxyl molecules on the surface of the metallic asteroid Psyche. The presence of hydrated minerals suggests a complex history for Psyche.
Jarmak et al. used Webb, shown in the bottom right corner of this illustration, to confirm the presence of hydrated minerals on the surface of Psyche. Image credit: Southwest Research Institute.
Psyche, a metal asteroid about 226 km (140 miles) in diameter, is one of the most intriguing targets in the main asteroid belt.
The object orbits the Sun between the orbits of Mars and Jupiter at a distance ranging from 378 to 497 million km (235-309 million miles) from the Sun.
Psyche takes about five Earth years to complete one orbit of the Sun, but only a bit over four hours to rotate once on its axis.
Unlike most other asteroids that are rocky or icy bodies, planetary scientists think Psyche is comprised mostly of metallic iron and nickel similar to Earth’s core.
On October 13, 2023, NASA launched the Psyche spacecraft, which is traveling 3.5 billion km (2.2 billion miles) to arrive at the asteroid in August 2029.
“Our understanding of solar system evolution is closely tied to interpretations of asteroid composition, particularly the M-class asteroids that contain higher concentrations of metal,” said Dr. Stephanie Jarmak, a researcher at the Harvard & Smithsonian’s Center for Astrophysics.
“These asteroids were initially thought to be the exposed cores of differentiated planetesimals, a hypothesis based on their spectral similarity to iron meteorites.”
The Webb data point to hydroxyl and perhaps water on Psyche’s surface. The hydrated minerals could result from external sources, including impactors
If the hydration is native or endogenous, then Psyche may have a different evolutionary history than current models suggest.
“Asteroids are leftovers from the planetary formation process, so their compositions vary depending on where they formed in the Solar Nebula,” said Dr. Anicia Arredondo, a researcher at Southwest Research Institute.
“Hydration that is endogenous could suggest that Psyche is not the remnant core of a protoplanet.”
“Instead, it could suggest that Psyche originated beyond the ‘snow line,’ the minimum distance from the Sun where protoplanetary disk temperatures are low enough for volatile compounds to condense into solids, before migrating to the outer main belt.”
However, the authors found the variability in the strength of the hydration features across the observations implies a heterogeneous distribution of hydrated minerals.
This variability suggests a complex surface history that could be explained by impacts from carbonaceous chondrite asteroids thought to be very hydrated.
Understanding the location of asteroids and their compositions tells us how materials in the Solar Nebula were distributed and have evolved since formation.
How water is distributed in our Solar System will provide insight into the distribution of water in other planetary systems and, because water is necessary for all life on Earth, will drive where to look for potential life, both in our Solar System and beyond.
“Using telescopes at different wavelengths of infrared light, the Southwest Research Institute-led research will provide different but complementary information to what the Psyche spacecraft is designed to study,” said Dr. Tracy Becker, a researcher at Southwest Research Institute.
The findings will appear in the Planetary Science Journal.
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Stephanie G. Jarmak et al. 2024. Estimate of water and hydroxyl abundance on asteroid (16) Psyche from JWST data. Planetary Science Journal, in press; doi: 10.3847/PSJ/ad66b9
This article is based on a press-release provided by Southwest Research Institute.
