Justice League of America #155 (1978)

UNDER THE MOONS OF EARTH! A second moon appears in Earth's sky, causing worldwide natural catastrophes. Realizing that their two worlds cannot exist in such close proximity, the leaders of Regna, the second moon, which is actually an Earth-like planet, set out to destroy life on Earth.  Green Lantern deduces that Regina is actually a world of the Earth's prehistoric past, somehow transferred in time to the present.  The Reginans reveal that this happened due to an inter-planetary war which also demolished the fifth planet of the solar system, thus creating the asteroid belt.  Superman is able to resolve the situation by transporting Regna into the distant future when life on Earth is extinct.