How did Mercury end up with such a huge iron core?
Quick Answer
Mercury’s core takes up about 70% of its radius, far more than Earth’s, likely because early impacts stripped away much of its original rocky mantle.
The Full Story
Mercury is unusually dense for a small planet, which is why scientists think it lost much of its outer silicate layer early in Solar System history. One leading idea is that giant impacts knocked away part of the mantle, leaving behind a world dominated by iron. Another possibility is that intense heat from the young Sun or chemical processes in the protoplanetary disk helped it form with an iron-rich composition. NASA’s MESSENGER mission, which orbited Mercury from 2011 to 2015, revealed more detail about the planet’s chemistry and geologic history. Mercury’s large core still generates a weak magnetic field today.
Key Facts
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