Analysis from the James Webb Space Telescope has revealed signs of water in the form of rust on the metal-rich asteroid Psyche.
Scientists using the James Webb Space Telescope (JWST) have identified water composition on the metal-rich asteroid Psyche, Live Science reported on August 14. This discovery indicates that hydrous materials exist in the form of rust, potentially shedding light on how this celestial body formed.
16 Psyche is quite unusual compared to the main asteroid belt located between Mars and Jupiter. With a width of 280 kilometers at its widest, this potato-shaped body was once thought to be entirely composed of metal. The asteroid’s extremely bright surface has led researchers to believe it could be the iron-rich core of a protoplanet, helping to explain how Earth and other rocky planets came into existence. Some researchers estimate that the rare metal composition of Psyche is worth $10,000 trillion.
Simulation of the metal asteroid Psyche. (Image: NASA).
In fact, the hypothesis regarding Psyche’s composition is the driving force behind NASA’s ongoing mission of the same name. Launched in October 2023, the spacecraft is expected to arrive at the asteroid in 2029 for in-depth study. However, over the past decade, new data regarding Psyche’s density and reflectance spectrum (the intensity of different wavelengths of sunlight reflected from the asteroid’s surface) suggests it is primarily composed of silicate mixed with metal.
In 2017, researchers found traces of another component: water. Spectra from the infrared range, at wavelengths we perceive as heat but cannot see, indicated signs of hydroxyl units, the OH molecule present in water.
The results demonstrate that the surface of Psyche may contain small amounts of water, possibly as ice or hydrous minerals. However, data collected by NASA’s ground-based Infrared Telescope Facility in Hawaii may have been influenced by water in Earth’s atmosphere. Additionally, researchers have not found clearer signs of water from higher infrared wavelengths, according to Stephanie Jarmak, a planetary scientist at the Harvard-Smithsonian Center for Astrophysics.
To determine whether Psyche actually contains water, Jarmak and scientists from several institutions in the U.S. and Germany utilized two JWST sensor instruments: the Near Infrared Spectrograph (NIRSpec) and the Mid-Infrared Instrument (MIRI), which can detect both shorter and longer infrared wavelengths. By directing these instruments toward the asteroid in March 2023, the research team collected reflectance spectral data from the northern pole of Psyche as it faced the telescope. Their findings will be published in the journal Planetary Science.
NIRSpec data revealed signs of hydroxyl, confirming the presence of water on the asteroid. Additionally, according to Jarmak, high-quality data allows for comparisons with hydroxyl signatures from other carbon-rich meteorites. The research team found that Psyche’s hydroxyl signature is similar to that of rusted carbon-rich meteorites. They concluded that the hydroxyls are bound to metals on Psyche, forming rust. However, MIRI data was insufficient to draw definitive conclusions. Water may exist but at a density below MIRI’s detection limit, less than half the density of water on the Moon, which corresponds to a drop of rain on one kilogram of soil.
Besides forming rust, hydroxyl groups on Psyche also provide clues about the asteroid’s formation process. If hydroxyls formed inside the asteroid, Psyche could have originated in the cold outer regions of the Solar System and gradually moved inward over millions of years. Current evidence suggests that a water-containing body collided with Psyche.
Future plans include precisely studying where hydrous metals are located on the surface of Psyche, including observing the southern pole of this asteroid, where many craters may have formed from impacts with water-containing objects. Despite its estimated value, Psyche is not among the targets for mining in space due to its location, which is three times the distance between Earth and the Sun, making it too far for cost-effective mining efforts.
