Scientists have discovered that Theia, a Mars-sized planet that crashed into Earth 4.5 billion years ago and created the Moon, was born in the inner solar system. A new study reveals this origin by analysing iron isotopes in lunar rocks, Earth rocks and meteorites.

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* Theia was a Mars-sized planet that hit Earth 4.5 billion years ago.

* The collision released debris that later formed the Moon.

* New study analysed iron isotopes in rocks and meteorites.

* Results show Theia formed in the inner solar system.

* Theia moved outward before crashing into early Earth.

* Earth and Moon have nearly identical isotopic fingerprints.

* Identical signatures match non-carbonaceous meteorites.

* These meteorites belong to the inner solar system region.

* Earth’s mantle contains molybdenum and iron likely from Theia.

* Study explains why Moon’s chemistry is similar to Earth’s.