Theories about the Moon's core. Illustration of three theories (top, centre and bottom) proposed to explain the positioning of the Moon's core (orange sphere). Across top, a series of impacts (upper left) strikes the nearside of the Moon and triggers volcanic eruptions and lava flows (upper right) that flood basins on the Moon's surface. Across centre, the second theory suggests that the gravitational attraction (blue arrow, centre left) of the Earth pulled the Moon's core off centre as it was forming, with later lava eruptions (centre right) similarly favouring the nearside of the Moon. Across bottom, a major impact (lower left) strikes the far side of the Moon, with the resulting dent (lower right) pushing the core off-centre, with lava eruptions again favouring the nearside.