It has baffled boffins with its metal rich core. Now, researchers say they have solved the mystery of how Mercury became the 'iron planet' - with its massive core making up 65% of its mass. They key was a giant interplanetary 'hit and run' with either Earth or Venus. New simulations show that Mercury and other unusually metal-rich objects in the solar system may be relics left behind by hit-and-run collisions in the early solar system with Earth or Venus. Mercury is the smallest and closest to the Sun of the eight planets in the Solar System, with an orbital period of about 88 Earth days.
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Mercury, the small, innermost planet has more than twice the fraction of metallic iron of any other terrestrial planet
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Researchers say key was a giant interplanetary 'hit and run' with either Earth or Venus
Its iron core makes up about 65 percent of Mercury’s total mass; @placeholder’s core, by comparison, is just 32 percent of its mass.