Different materials resist corrosion in space differently. For example, aluminium is slowly eroded by atomic oxygen, while gold and platinum are highly corrosion-resistant. Gold-coated foils and thin layers of gold on exposed surfaces are therefore used to protect the spacecraft from the harsh environment. Thin layers of silicon dioxide deposited on the surfaces can also protect metals from the effects of atomic oxygen; e.g., the Starshine 3 satellite aluminium front mirrors were protected that way. However, the protective layers are subject to erosion by micrometeorites.