JWST spots hydration on metal asteroid Psyche

Researchers analysing data from the James Webb Space Telescope (JWST) have found evidence that an object in the asteroid belt is “hydrated”.

This doesn’t mean that the asteroid has reached its daily fluid intake goals. The finding refers to the presence of hydroxyl molecules (an oxygen atom bound to a hydrogen atom) on the surface of the asteroid named Psyche.

Object crashing into asteroid with james webb space telescope in the corner
Artist impression of an object crashing into an asteroid, hydrating it, next to the JWST. Credit: Southwest Research Institute.

Psyche is about 222 kilometres in diameter and orbits the Sun along with millions of other objects in the Main Asteroid Belt which sits between the orbits of Mars and Jupiter. It was first observed by Italian astronomer Annibale de Gasparis in 1852.

It is largely metallic, leading to its designation as an M-class asteroid. Psyche could be the leftover core of a planet which experienced a catastrophic collision and never reached planetary maturity.

In October 2023, NASA launched the Psyche spacecraft which is traveling to the asteroid. The spacecraft’s 3.5-billion-km journey is due to see it arrive at the asteroid in August 2029.

Hydrated minerals present on the asteroid suggests a complex history for Psyche and will aid the NASA spacecraft’s mission to understand this object.

Understanding interesting asteroids like Psyche could help us understand the origins of the solar system and even life on our planet.

“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,” says Stephanie Jarmak from the Center for Astrophysics | Harvard & Smithsonian in the US.

Jarmak is lead author of a paper published on the research into Psyche which is published in the Planetary Science Journal. She completed much of the research as part of the Texas-based Southwest Research Institute (SwRI).

The fact that hydroxyl, and potentially water, are present on the asteroid’s surface raises a question: was Psyche hydrated by impacts from external bodes, or is the hydration native to the asteroid (endogenous)?

If the hydration is not the result of external impacts, then it could suggest that Psyche has a different evolutionary history than current asteroid formation models.

“Asteroids are leftovers from the planetary formation process, so their compositions vary depending on where they formed in the solar nebula,” says co-author Anicia Arredondo from the SwRI. “Hydration that is endogenous could suggest that Psyche is not the remnant core of a protoplanet.”

The JWST data shows that hydration is not even across Psyche’s surface which could point to the presence of hydroxyl molecules due to impacts by highly hydrated asteroids.

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