Complex sentence: M-type asteroids are thought to be composed primarily of nickel and iron, which if proven to be true means that 7474 (1992 TC) may one day become an important source of raw materials in space.
Split into simpler sentences: M-type asteroids are thought to be composed primarily of nickel and iron. If this is proven to be true, 7474 (1992 TC) may one day become an important source of raw materials in space.