According to a study published online in Nature Geoscience July 6, Mercury and other unusually metal-rich objects in the solar system may be relics left behind by collisions in the early solar system that built the other planets.
Asphaug and Andreas Reufer of the University of Bern developed a statistical scenario for how planets merge and grow based on the common notion that Mars and Mercury are the last two relics of an original population of maybe 20 bodies that mostly accreted to form Venus and Earth. These last two planets lucked out. 'How did they luck out? Mars, by missing out on most of the action – not colliding into any larger body since its formation – and Mercury, by hitting the larger planets in a glancing blow each time, failing to accrete,' explains Asphaug.
According to Reufer, who performed the computer modeling for the study, 'Giant collisions put the final touches on our planets. 'Only recently have we started to understand how profound and deep those final touches can be. 'The implication of the dynamical scenario explains, at long last, where the ‘missing mantle’ of Mercury is – it’s on Venus or the Earth, the hit-and-run targets that won the sweep-up.'
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