Dr Shearer agreed the 4.5-billion-year ages of the meteorites indicated the likely source was an asteroid. “The history of this rock involves partial melting on a fairly primitive body,” he explained. Even if the rocks had been blown off Venus in an impact 4.5 billion years ago, they could not have drifted in space for such a vast length of time before landing in Antarctica recently, scientists said.
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The identity of the object that spawned the two meteorites may be elusive, but researchers have been able to draw up a basic profile. They know, for instance, that the parent body had “differentiated” – that is, had been reprocessed into a layered object, usually with a core, a mantle and a crust. Stony meteorites which have undergone this reprocessing are known as achondrites.