ASTEROIDS

Weighing Psyche

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Science  23 Apr 2021:
Vol. 372, Issue 6540, pp. 357
DOI: 10.1126/science.372.6540.357-a

Artist's conception of the metal-rich asteroid Psyche

IMAGE: NASA/JPL-CALTECH/ASU

Remote observations have shown that the asteroid (16) Psyche has a metallic surface, usually interpreted as being the exposed iron core of a protoplanet that was disrupted by a past giant impact. Siltala and Granvik analyzed astrometric observations of 10 smaller asteroids that experienced close encounters with Psyche between 1974 and 2019. The gravitational perturbations of these asteroids' orbits allowed the authors to derive the mass of Psyche. Combined with its known diameter, this leads to a bulk density that is far too low for a solid iron body. The results support an alternative interpretation: that Psyche's surface formed by volcanic eruptions of liquid iron sulfide. The asteroid is due to be visited by a spacecraft (also named Psyche) in 2026.

Astrophys. J. 909, L14 (2021).

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