Is Psyche really the core of a lost planet?
What radar, density and spectra say about Psyche's metal — and the competing ideas for how it formed.
Published 2026-10-23
Psyche is famous as “the metal asteroid,” and NASA picked it for a mission because it may contain a large amount of metal from the core of a planetesimal — an early planetary building block.[1] But the picture has grown more complicated.
Clue 1: radar
Radar observations from Earth indicate an iron-nickel composition.[6] Psyche's radar albedo ranges from about 0.22 to 0.52 — two to four times as high as most main-belt asteroids — and in a few places it is nearly double its background value, suggesting concentrations of metal.[5]
Clue 2: density
JPL lists Psyche's bulk density at about 4.2 g/cm³.[3] Solid iron-nickel from iron meteorites is about 7.9 g/cm³.[5] So Psyche cannot be a solid metal ball: it must be porous, mixed with rock, or both. NASA now says the best analysis points to a mixture of rock and metal, with metal making up 30% to 60% of its volume.[1]
Clue 3: spectra
In 2016, observations at NASA's Infrared Telescope Facility in Hawaii found signs of hydroxyl, which may point to hydrated minerals. Because Psyche is thought to have formed dry, these may have been delivered by impacts of smaller carbonaceous asteroids.[5]
The leading ideas
- Exposed core: repeated hit-and-run collisions stripped away a planetesimal's rocky mantle, leaving much of its metal core.[1]
- Mixed rubble: Psyche re-formed from a mix of metal and rock, which might make it a parent body for mesosiderites, stony-iron meteorites made of roughly equal parts metal and silicate.[5][9]
- Other analogs: researchers have also compared Psyche with enstatite chondrites and bencubbinites, meteorites with similar bulk densities.[5]
How we will find out
From orbit, the Psyche spacecraft's gamma-ray and neutron spectrometer will measure surface composition, its magnetometer will look for a remnant magnetic field, and its gravity experiment will probe the interior.[1] Until the spacecraft arrives in 2029, no one knows exactly what Psyche looks like up close.[1]
Numbered citations link to the sources list on the 16 Psyche overview page.