Asteroids hold quantities of rare metals that sank into Earth's core early on. Small asteroids have accessible deposits, making them attractive.
Elements beyond uranium would be a huge discovery. But most have short half-lives, decaying quickly after formation.
Models suggest a region of stable heavy nuclei around element 114. But expected half-lives are under a century.
No elements beyond uranium have been found naturally on Earth. Evidence in meteorites is controversial.
A new study claims asteroid Polyhymnia may harbor superheavy elements based on its calculated high density. But data is limited.
Polyhymnia's density estimate is considered unreliable. No observations confirm superheavy elements are present.
Psyche will study asteroid worth quadrillions in rare metals, but likely no ultra-heavies.