Moon Formation Could Have Taken Just Hours, New Study Finds 2026

The formation of the Moon may have taken just hours, not months or years, according to a new study that challenges long-held assumptions about the giant impact hypothesis. Researchers at the Southwest Research Institute (SwRI) and the University of Arizona found that when material strength is included in simulations, the Moon can form in as little as 5 hours.

This finding upends the traditional view that the Moon coalesced slowly from a disk of debris over tens to hundreds of years. Instead, the new model suggests that under certain conditions, the Moon could have formed in less time than a typical workday.

Why the Giant Impact Hypothesis Needed a Second Look

The giant impact hypothesis proposes that a Mars-sized protoplanet named Theia collided with the early Earth, ejecting material that eventually formed the Moon. Previous simulations of this event generally ignored the resistance of materials, assuming that the immense energy involved made strength negligible.

However, the SwRI and University of Arizona team decided to add material strength to their models. They discovered that this factor is far from negligible—it significantly alters the outcome of the collision.

What the Simulations Revealed

Without accounting for material strength, the simulations showed that Earth accretes about 91% of Theia and produces a debris disk that slowly forms the Moon. But when strength is included, the results change dramatically.

In some scenarios, the Moon forms directly from the ejected material in a matter of hours. In others, the process takes longer. The key variable is the temperature of Earth and Theia at the time of impact, which affects how materials behave under extreme conditions.

• Material strength matters: Including it in simulations changes the outcome from slow accretion to rapid moon formation.
• Temperature is critical: The thermal state of Earth and Theia determines whether the Moon forms in hours or over longer periods.
• Direct formation: In some cases, the Moon can coalesce directly from the impact debris, bypassing a long disk phase.
• New constraints: The study provides fresh insights into the conditions of the early Earth-Moon system.

How the New Model Compares to Previous Theories

The traditional view held that the Moon formed from a disk of debris over millions of years. The new model suggests a much faster timeline under certain conditions. The table below summarizes the key differences.

What This Means for Our Understanding of the Moon

If the Moon could form in hours, it would have significant implications for our understanding of planetary formation. It suggests that large impacts can produce satellites rapidly, which might be common in the universe. The longer history behind the story is traced in Saturn's South Pole Reveals a Rare Decagonal Cloud Pattern. More on the surrounding debate is collected in Fermi Explorer Mission: A 2029 Probe to Alpha Centauri.

Moreover, the study highlights the importance of including material properties in simulations. Small-scale impacts have long been modeled with strength, but large-scale events were thought to be dominated by gravity. This research shows that strength can still play a role. The background to this story is set out in SpaceX Rocket Moon Impact: What Science Saw in the Plume. A related thread runs through SpaceX Rocket Crashes into Moon: What It Means for Space Debris. Earlier coverage in China's Dixing-3 Bed Rest Study for Moon Missions Explained shows how the argument developed.

What to Watch Next

Future studies will need to refine the temperature conditions and material properties to determine how often rapid moon formation occurs. The team's findings also raise questions about the composition of the Moon and whether it matches the expected debris from a fast-forming event. A closer look at the same subject appears in 20 Cats Have Taken Their Job To Troll Their Owners Too Seriously. Anyone following the wider picture can start with 30 Famous Actors Who Might Have Taken Things Too Far For A Role. The same theme surfaces in Influencers Have Taken Over My City: If You Can't Beat 'Em, Join 'Em, which takes a different angle.

As scientists continue to explore the Moon's origins, this study reminds us that even well-established theories can be overturned by new data and improved modeling techniques. Context on how this played out before sits in NASA Sends Three Fully Autonomous Robots to the Moon. A companion piece, Fungi: The Unexpected Ally for Growing Food on the Moon and Mars, approaches the same subject from another angle.