Has Mercury always rotated as slowly as it does now?
Probably not. When Mercury first formed, it may have spun around its axis very quickly. However, the Sun's gravity has pulled on the planet, slowing it down to its present speed.
Why does Mercury have such a high proportion of metals?
One theory is that Mercury didn't form near the Sun. It might have been a metal-rich asteroid from another part of the solar system. The more accepted theory is that Mercury is mostly metal because it formed so close to the Sun. Only metals could withstand the heat
