Illustration of the surface of Mercury TIM BROWN / SCIENCE PHOTO LIBRARY
A giant impact four billion years ago could have caused Mercury to lose most of its mantle to deep space, potentially explaining one of the planet’s key mysteries.
Mercury is unusual compared with other rocky planets in the solar system, as its iron core accounts for more than 80 per cent of its radius. Earth’s core, by comparison, makes up just 50 percent of the planet’s radius. This makes it very dense, with just a thin mantle around 500 kilometres thick above the core.
Astronomers have long…
