It started as a routine data-quality check. But as Robert Wagner, a scientist with NASAâs Lunar Reconnaissance Orbiter (LRO), scanned a giant Moon map on his computer screen, an unusually large bright spot circled by a dark halo caught his eye, as it implied that surface material in that area had been shaken up.
âI just stopped, dropped everything, and started looking into what that spot was,â said Wagner, an image-processing specialist from Intuitive Machines who works with data from the Lunar Reconnaissance Orbiter Camera (LROC) system.
By comparing before and after images of the Moon, Wagner realized he had discovered the largest, newly formed crater ever found in the solar system, as scientists reported Wednesday in Science Advances. This discovery highlights the value of NASAâs Moon orbiter data in studying a dynamic landscape as the agency advances a sustained human presence and expanded scientific and commercial activity on the Moon.
Officially named McGetchin after pioneering lunar scientist Tom McGetchin, the crater formed on the Moonâs eastern edge sometime between April 11 and May 22, 2024, after a comet or asteroid the size of a three- to six-story building hit the surface.
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The crash left a crater, 728 feet wide, that spans the length of two football fields. And at 141 feet deep, the crater could fit three vertically stacked yellow school buses.
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Scientists estimate that an impact of this magnitude happens on the Moon about once in a century or even longer.
Moon takes some hits
For more than 17 years, LRO has been circling the Moon and using its seven instruments to map the topography, surface composition, temperature, and radiation environment there. The spacecraftâs team has identified at least 1,000 new impact craters throughout the mission and flagged 100,000 more surface changes from an object smashing into the Moon or from the debris that flung out after.
With no atmosphere to slow them or burn them up, space rocks and other objects easily reach the lunar surface. Most are much smaller compared to the object that carved out McGetchin crater. The smallest craters scientists can distinguish from LRO images are about 30 feet wide, the length of a three-story building laid on its side, made by rocks about 43 inches wide, the size of a monster-truck tire. Scientists estimate that impacts of this scale produce about 140 new craters across the Moon each year. But most new ones are made by microscopic projectiles that leave holes too small to identify in orbital images.
With its numerous instruments, the spacecraft can observe changes to the lunar surface that arenât apparent in the LROC images alone. After the crater was discovered, scientists working with LROâs thermal instrument, Diviner, made follow-up observations of the site. They found a 4-mile-wide area around the crater that is about 16 degrees Fahrenheit cooler at night than its surroundings.
Reporting in a second paper Wednesday in the same journal, researchers say that the cooling happens because the impact fluffs up the regolith around the crater, making it less dense and therefore less able to retain heat.
The large extent of this âcold spotâ is striking, scientists say, because it shows that impacts can modify the Moonâs surface far beyond the crater itself. These physical changes could affect how rover wheels interact with the surface, for instance.
