What Existed Before the Moon?

Before the Moon, there were two distinct planetary bodies: proto-Earth and a roughly Mars-sized planet called Theia. These celestial bodies were the primary precursors to both our planet Earth and its natural satellite, the Moon.

The Planetary Precursors

Before the formation of the Moon, the early solar system was a chaotic place, with numerous planetesimals and protoplanets interacting. Among these were:

• Proto-Earth: This was the early, less developed version of our current Earth. It was accumulating material in its orbit around the Sun.
• Theia: A significant body, comparable in size to the planet Mars, that co-orbited the Sun in the vicinity of proto-Earth.

These two bodies are central to the most widely accepted scientific explanation for the Moon's origin.

The Giant-Impact Model

The prevailing scientific theory for the Moon's formation is the Giant-Impact Model. This model posits a cataclysmic event that reshaped our solar system's early history:

• The Collision: At some point in Earth's very early history, proto-Earth and Theia collided in a massive, high-energy impact.
• Ejection of Debris: This colossal collision generated an immense amount of molten and vaporized rock, which was ejected into orbit around the newly forming Earth.
• Accretion and Formation: Over time, this ejected debris gradually coalesced and accreted through gravitational forces, eventually forming the Moon we see today.

This model not only explains the existence of the Moon but also provides insights into its composition and orbital characteristics, which are distinct from other planetary moons. The Moon is essentially a cosmic byproduct of this violent early interaction between proto-Earth and Theia.

Key Pre-Lunar Bodies