Psyche is a large, peculiar asteroid that orbits the Sun in our solar system’s asteroid belt. Although most asteroids are made primarily of rock or ice, Psyche is abundant in metal, suggesting that it could be the remnant core of an early planet. Now Elkins-Tanton et al. report that Psyche may have a higher ratio of rock to metal than previously hypothesized.
In preparation for a NASA mission to Psyche set to launch in 2022, the researchers reviewed and analyzed reports on the latest observations of the asteroid, including data from mass and volume calculations, radar measurements, and investigations of Psyche’s spectral signature.
The analysis suggests that Psyche, which is about 226 kilometers in diameter, has a density of 3,400–4,100 kilograms per cubic meter. And although earlier observations suggested that the asteroid consists almost entirely of iron and nickel, it now appears that those metals make up only 30%–60% of its volume, with the rest consisting of silicate rock and pore space.
The origin of Psyche, the details of its structure, and the specific kinds of rock it contains remain mysterious. Is Psyche indeed the core of an early planet that was stripped of its outer layers by impacts with other objects? If so, what did that planet look like, and what kinds of collisions and other conditions shaped its fate? Or did it form in some previously unimagined scenario?
The new findings help constrain the possible answers to these questions, providing valuable context for the upcoming mission to Psyche—the first mission to a metallic asteroid. Observing Psyche up close should provide final answers about the asteroid and could improve understanding of how Earth and other planets formed. (Journal of Geophysical Research: Planets, https://doi.org/10.1029/2019JE006296, 2020)
—Sarah Stanley, Science Writer