Small bodies · Space Codex
16 Psyche
An asteroid about 220 km across that may be the exposed iron-nickel core of a shattered protoplanet.
A metal-rich world NASA is flying to
Artist's concept. 16 Psyche has never been imaged in enough detail to show its true shape or surface. Any depiction of it is an illustration based on measurements, not a photograph.
At a glance
Key points
NASA's Psyche spacecraft arrives in August 2029.
- Possibly the exposed core of a protoplanet
- NASA's Psyche spacecraft arrives in August 2029
- Dull grey, not chrome: albedo only 0.12
Why it matters
Rocky planets have metal cores we can never visit. If Psyche is a stripped core, it is a chance to see how planetary interiors were built.
The journey there
The spacecraft is pushed by solar-electric propulsion: a faint but continuous thrust sustained for years rather than one big burn. On 15 May 2026 it passed 4,609 km above Mars, gaining about 1,600 km/h and tilting its orbit by about one degree without spending propellant. It also carried NASA's Deep Space Optical Communications test, which returned data by laser from as far as 494 million km before the experiment ended in September 2025.
What the spacecraft will measure
From orbit, a multispectral imager will map Psyche's landforms and colours, and a gamma-ray and neutron spectrometer will measure elements such as iron and nickel. Magnetometers will look for magnetism frozen into the rock: finding it would be strong evidence that Psyche once had a molten, churning core that generated its own field. Tracking the spacecraft's radio signal will reveal the gravity field, and with it how mass is spread through the interior.
What we still don't know
How much of Psyche is metal and how much is rock; its density sits between the two. Laboratory spectral matching published in 2021 suggested a surface of roughly 80% metal mixed with rock and carbon-rich debris, and a porosity near 35%, more like a loosely packed pile than a solid ingot; other estimates differ. No real surface map exists yet: any image of it is an artist's concept until 2029.
Missions
- 2023–
Mars gravity assist 15 May 2026; arrives at asteroid Psyche Aug 2029.
Related entries
- Psyche (mission)NASA's journey to a metal-rich asteroid
- Main asteroid beltRocky debris between Mars and Jupiter
Sources
- NASA JPL: Deep Space Optical Communications demo exceeds expectations (opens in a new tab)
- Cantillo et al. 2021, Planetary Science Journal (opens in a new tab)
- JPL Small-Body Database: 16 Psyche (opens in a new tab)
- NASA Science: Psyche mission (opens in a new tab)
- NASA JPL: Psyche mission aces Mars flyby (opens in a new tab)
Last reviewed against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.