Scientists suggest Earth once had a neighboring planet whose collision may have created our Moon.

Did a Lost Planet Create Our Moon?

New research hints at a cosmic neighbor that shaped Earth’s destiny

For decades, scientists have debated the origins of Earth’s Moon. The leading theory has long been the “giant impact hypothesis”—the idea that a Mars-sized body collided with Earth billions of years ago, ejecting debris that eventually coalesced into our Moon. Now, new research adds a fascinating twist: this impactor may not have been a random wanderer, but rather a planet that once orbited right next to Earth.

According to the study highlighted by Live Science, researchers propose that an extra-solar system planet, nicknamed Theia, may have shared Earth’s orbit in the early days of the solar system. This unusual arrangement, known as a co-orbital configuration, could have persisted until gravitational instabilities forced Theia into a catastrophic collision with Earth. The aftermath of this collision would explain not only the Moon’s formation but also key aspects of Earth’s composition.

Why this matters

Moon’s composition mystery: The Moon’s rocks are strikingly similar to Earth’s mantle, which has puzzled scientists. A nearby co-orbital planet would have had a similar chemical makeup, making the match more plausible.
Earth’s tilt and seasons: The collision may have tilted Earth’s axis, giving us the seasonal cycles that shape life today.
Planetary dynamics: The idea that planets can share orbits challenges traditional views of solar system stability and opens new avenues for exoplanet research.

A cosmic neighbor lost to history

Theia’s existence is hypothetical, but simulations show that such co-orbital planets are possible. If true, Earth’s Moon is not just a byproduct of chance—it is the legacy of a vanished world that once circled the Sun alongside us.

Looking ahead

Future missions studying lunar geology, combined with advanced computer models, may help confirm whether Earth’s Moon truly carries the fingerprints of this lost planet. If so, our closest celestial companion is also a monument to one of the most dramatic events in planetary history.

Source: Live Science

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