Psyche: A unique asteroid in the main belt
Asteroid 16 Psyche, located in the main asteroid belt between Mars and Jupiter, is an unusual object, spanning 173 miles (280 kilometres) at its widest.Initially believed to be entirely metallic, Psyche’s shiny surface led researchers to theorise that it might be the iron-rich core of a planetesimal, potentially offering clues about the formation of Earth and other terrestrial planets. Some estimates place the value of Psyche’s metal components at an astonishing $100,000 quadrillion.
This hypothesis about Psyche’s composition inspired NASA’s ongoing Psyche mission, launched in October 2023, with plans to reach the asteroid by 2029 for a detailed study.
New insights into Psyche’s composition
However, recent data has revealed that Psyche might not be purely metallic. Over the past decade, new information about the asteroid’s density and reflectance spectra indicates that it is likely a mix of silicate and metal.
In 2017, researchers detected traces of water on Psyche. Infrared spectra revealed the presence of hydroxyl units (OH molecules), a component of water. These findings suggested that small amounts of water might exist on Psyche’s surface, either as ice or hydrated minerals. However, the results were inconclusive, as the data collected from Earth-based telescopes might have been contaminated by Earth’s atmosphere. Additionally, a more definitive water signature, which has been used to detect water on the Moon, was not found on Psyche.
JWST’s observations of Psyche
To confirm the presence of water, planetary scientist Stephanie Jarmak and a team of researchers used two of JWST’s infrared instruments—the Near Infrared Spectrograph (NIRSpec) and the Mid-Infrared Instrument (MIRI). In March 2023, they directed these instruments toward Psyche, capturing spectra from the asteroid’s north pole. Their findings, accepted by the Planetary Science Journal and available as a preprint on arXiv, showed a hydroxyl signature consistent with rust-bearing, carbon-rich meteorites, suggesting that hydroxyls are bonded to metals on Psyche, forming rust.
Psyche: Uncertainty regarding water’s presence
While the MIRI data did not show a conclusive signature of water, the researchers cannot rule out its presence. Water might be located in areas of Psyche that JWST could not observe, or it could exist in concentrations too low for MIRI to detect, less than half the amount found on the Moon.
Psyche’s origin clues
Psyche’s hydroxyl groups also offer clues about its origins. If these groups formed within the asteroid, it could indicate that Psyche originated in the cold outer regions of the solar system before moving inward over millions of years. However, the current evidence suggests that water-bearing asteroids collided with Psyche, contributing to its current composition.
Future research and space mining prospects
Future research aims to map the distribution of hydrated metals on Psyche’s surface, including observations of its south pole, which features a large crater possibly formed by a collision with a water-bearing impactor.
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