The bit of nebula that formed Mercury formed a dense metallic core with a thin silicate crust on the surface. Asteroids bombarded the surface and internal lava flowed out and formed a newer crust. Not long after, Mercury's core cooled down and shrunk to a smaller size, resulting with the outer crust cracking. Another wave of lava ensues, covering the old crust.
Smaller meteorites bombarded Mercury, forming a dusty surface known as the regolith. On occasion, large asteroids would crash into Mercury creating bright rayed craters.
Silicate:
a salt in which the anion contains both silicon and oxygen, esp. one of the anion SiO 4 2−. • any of the many minerals consisting primarily of SiO 4 2− combined with metal ions, forming a major component of the rocks of the earth's crust.
Metallic:
of, relating to, or resembling metal or metals : metallic alloys | a curious metallic taste. • (of sound) resembling that produced by metal objects striking each other; sharp and ringing : the terrifying, metallic clamor of the fire-engine bell. • (of a person's voice); emanating or as if emanating via an electronic medium : a metallic voice rasped tinnily from a concealed speaker. • having the sheen or luster of metal : a metallic green sports car.
Crater:
a large, bowl-shaped cavity in the ground or on the surface of a planet or the moon, typically one caused by an explosion or the impact of a meteorite or other celestial body. • a large pit or hollow forming the mouth of a volcano. • a cavity or hole in any surface.
