Complex sentence: The impactors may have been gravitationally bound as a binary asteroid, a suggestion first made by Thomas Wm. Hamilton in a 1978 letter to Sky & Telescope magazine in support of the then-controversial theory that asteroids may possess moons.
Split into simpler sentences: The impactors may have been gravitationally bound as a binary asteroid. This suggestion was first made by Thomas Wm. Hamilton in a 1978 letter to Sky & Telescope magazine in support of the then-controversial theory that asteroids may possess moons.