Scientists have discovered a crater on the moon that’s bigger than the Roman Colosseum and is the result of a powerful impact two years ago that initially went undetected.

The steep-sided hole measured about 728 feet across, the length of two football fields, and up to 141 feet deep, equivalent to three vertically stacked yellow school buses, according to NASA. It’s the solar system’s biggest known impact crater carved out in recent times.

Such a large-scale event is estimated to occur only once every 132 years, researchers said, making this a treasure trove of information as NASA prepares to build a base for astronauts on the moon.

“This event constitutes a statistically rare, effectively once-in-a-lifetime observation,” the scientists wrote in one of two studies appearing on the subject Wednesday in the journal Science Advances.

NASA’s Lunar Reconnaissance Orbiter spotted the crater on the moon’s near side sometime between April 11 and May 22, 2024, soon after it was formed when an incoming fragment of an asteroid or comet the size of a three- to six-story building hit the surface. The moon strike escaped real-time detection by telescopes on Earth and in space.

LRO’s wide-angle images were not identified in the crush of data until August 2025. The spacecraft gathered more detailed pictures last fall, followed by confirmation of the discovery early this year.

The crater — named for the late Thomas McGetchin, a former director of Houston’s Lunar and Planetary Institute — is three times bigger than the previous record-holder found by the LRO a decade ago. Pockmarked since ancient times, the moon bears some of the solar system’s largest impact craters, including one that stretches more than 1,500 miles across.

This latest impact churned the lunar surface for more than 66 miles. Dust and rocky soil were hurled away at a higher angle than expected, according to Mark Robinson, chief scientist for the LRO’s cameras who works at Intuitive Machines. Robinson was the lead author for one of the studies.

A separate study identified a 4-mile-wide cold spot around the new crater, consistent with a loosening of the moon’s top soil. Co-author David Paige of the University of California, Los Angeles, likens it to gardening.

“We’re now thinking of impacts as a way to garden the regolith — churning the sediments and putting stuff above that’s usually below the surface,” Paige said in a statement.

NASA’s Lunar Reconnaissance Orbiter has circled the moon since 2009, providing a close-up view of the lunar surface as the space agency prepares to send astronauts back. The LRO’s numerous crater discoveries since its launch show that the moon’s top inch of soil is being overturned by ejected material every 80,000 years, faster than previously thought, according to Robinson.

Contrary to the popular belief that the Apollo moonwalkers’ dusty lunar footprints will last forever, they will “definitely be long gone in that time frame,” Robinson said in an email.

The next step is to calculate the risk of ejected crater material striking NASA’s planned moon base, he added. “That information will help engineers harden structures so one won’t have to worry about damage, or maybe worry less.”