Could Psyche be the core of the planetesimal that struck Earth and formed the Moon?

The metallic asteroid Psyche, shown in this artist’s concept, may be the exposed iron-nickel core — or a fragment of one — from a larger object early in the solar system. But it is likely not associated with the object that created Earth’s Moon. Credit: Peter Rubin/NASA/JPL-Caltech/ASU

Could Psyche be the core of the planetesimal body that struck Earth and resulted in the formation of the Moon?

Colton Brooks
Virginia Beach, Virginia

Psyche appears to be an iron core, or part of one, produced during the history of collisions experienced by a fairly large asteroid with other large asteroids. The collision or collisions were likely between unusually large bodies, since Psyche itself is a relatively large asteroid (it was only the 16th discovered, and by virtue of its size can reflect a lot of light), with dimensions of about 173 by 144 by 102 miles (278 by 232 by 164 kilometers).

There seems to be little reason to associate it with the probable large collision that formed Earth’s Moon, however, because Psyche has a nearly circular orbit in the asteroid belt, so it is unlikely to have come close to Earth. The object responsible for the Moon-forming collision is thought to have been one of the larger bodies that formed in the inner solar system region of Earth and Venus, and impacted Earth fairly late during the growth of our planet.

William K. Hartmann
Senior Scientist Emeritus, Planetary Science Institute, Tucson, Arizona