Psyche

Asteroid · Main-belt asteroid (metallic) · orbits Sun

Psyche is unlike almost anything else in the belt: a 226-km body whose surface appears rich in bare metal rather than rock or ice. It may be the exposed iron core of a shattered protoplanet whose rocky layers were stripped away by collisions - or a strange metal-rich body that never fit the textbook categories at all.

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Quick facts

Radar echoes from Psyche are unusually strong - the fingerprint of a metal-rich surface.
NASA’s Psyche spacecraft launched in 2023 and arrives in 2029, the first mission to a metal world.
It spins once every 4.2 hours - a very short day for so large a body.

A planetary core in plain sight?

Earth’s iron core lies beneath 2,900 km of rock, forever out of reach - no mission will ever visit it. If Psyche really is the battered core of a protoplanet, it offers something extraordinary: a chance to orbit and study the kind of metal world that hides at the centre of every rocky planet, including our own.

Physical characteristics

Diameter	226 km
Dimensions	278 × 238 × 171 km
Mass	2.300e+19 kg
Rotation period	4.2 h
Geometric albedo	0.12

Atmosphere and composition

Atmosphere	None.
Composition	Metal-rich: iron and nickel mixed with silicate rock; the exact proportions are unknown.

Discovery

Discovered by	Annibale de Gasparis
Year	1852
How	Naples Observatory refractor

Missions

Psyche NASA · Orbiter · 2023 · en route

Psyche is cruising on solar-electric propulsion toward the metal-rich asteroid of the same name, arriving in 2029. The asteroid may be the exposed nickel-iron core of a shattered planetesimal - a chance to study a planetary core without digging.

What is still uncertain

Psyche’s density and metal content are only loosely constrained until NASA’s Psyche orbiter measures them directly.