According to Zecharia Sitchin's interpretation of Sumerian cosmology, there is a hypothetical planet which follows a long, elliptical orbit, reaching the inner solar system roughly every 3,600 years. This planet is called Nibiru (the planet associated with Marduk in Babylonian cosmology). Nibiru collided catastrophically with Tiamat, another hypothetical planet that was between Mars and Jupiter. The collision formed the planet Earth, the asteroid belt, and the comets. Tiamat, as outlined in the Enûma Elish, is a goddess. According to Sitchin, however, Tiamat may have been what we now know as Earth. When struck by one of planet Nibiru's moons, Tiamat split in two. On a second pass Nibiru itself struck the broken fragments and one half of Tiamat became the asteroid belt. The second half, struck again by one of Nibiru's moons, was pushed into a new orbit and became today's planet Earth.