Lost World
A rare pallasite meteorite has revealed evidence of a destroyed planetary embryo — a differentiated rocky world ~600 km across — that once orbited the young Sun before being shattered in a cataclysmic collision ~3.9 billion years ago, its remains now scattered through the asteroid belt.
Early Solar System · ~3.9 Gya
Mercury
Venus
Earth
Mars
Planet V (lost world)
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Pallasite Structure
Olivine crystals locked inside an iron-nickel metal matrix — a texture that only forms at the core-mantle boundary of a large, gravitationally differentiated world.
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Cooling Rate: 0.5°C/Myr
Far slower than any known asteroid. This rate implies a body large enough to retain internal heat for tens of millions of years — at least 600 km in radius.
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Unique Oxygen Isotopes
Δ¹⁷O values match no known meteorite group, placing the lost parent body in a distinct isotopic reservoir of the early solar nebula.
Evidence Chain