The moon would have formed in just a few hours. The theory that changes everything we know about Earth's natural satellite

Credit image: NASA
Credit image: NASA

Article by: Andacs Robert Eugen, on 25 October 2022, at 09:02 am PDT

Since the 1980s, the leading theory regarding the formation of the Moon has been that a massive body, perhaps the size of Mars, crashed into Earth billions of years ago, spewing out a quantity of gas, magma, and metals that led to the formation of the Moon in decades or even hundreds of years.

A study recently published in The Astrophysical Journal Letters suggests a bold new idea: The Moon could have formed very quickly, from impact material thrown into a wide orbit, in just a few hours. If this is true, the research, which focused on hundreds of extremely high-resolution computer simulations of such a collision, could help solve a long-standing dilemma for scientists - namely why the lunar crust looks so similar to that of the Earth.

The idea also offers potential answers to why the Moon is tilted and has a thin outer layer. Cosmologists want to piece together what happened, not only to complete the story of the Moon's origin but also to explain a defining moment in Earth's evolution.

NASA and its collaborators made a quick two-minute animation that tries to capture what this process would have looked like. Over the decades, a planet, which scientists have named "Theia," hits a primitive version of Earth like a paintball, spewing a jumble of planetary debris into the cosmos. However, instead of forming a thin disk of dust and rocks, it splits into another structure that has been pushed further away by Earth's Gravity.

For years, scientists ran computer models of the giant impact at lower resolution without the two bodies actually breaking apart. In this case, NASA collaborated with Durham University's Institute for Computational Cosmology in England to run simulations at up to 1,000 times the standard resolution, testing and observing different impact angles, velocities, planetary spins, and dimensions.

Understanding the composition of the Moon is not easy, in part because scientists base their knowledge on a small collection of rocks from a very small area near the lunar equator. NASA scientists are looking forward to the Artemis moon landing missions, which will explore a completely different region to gather more data, including samples from deep within the Moon.