Moon impacts are more common than we thought, study finds

The moon might be one of the most well-studied objects in space, but that doesn’t mean that we know all of its secrets just yet, as demonstrated by a newly-published research paper that reveals the lunar surface contains far more craters than researchers had previously predicted.

Comparing before-and-after images of the same basic region of the moon captured at different times by the Lunar Reconnaissance Orbiter (LRO), senior researcher Emerson Speyerer and his Arizona State University colleagues discovered 33% more craters than had been detected earlier, according to New Scientist and Engadget reports published on Wednesday.

What that means, Speyerer’s team explained, is that the small meteors that constantly bombard the moon are constantly forming new craters and impact basins which could pose a serious threat to any human settlements or refueling stations constructed there in the foreseeable future.

“If you are an astronaut sitting on the surface, you don’t necessarily have to worry about being directly hit by a meteorite,” he told New Scientist. “But you would have to worry about all these secondaries, that are coming from kilometers and kilometers away.” The LRO researchers have published their findings in this week’s edition of the peer-reviewed journal Nature.

Observing the moon’s regolith evolve in real-time

Speyerer and his colleagues compared 14,000 images collected by the orbiter at different times and counted 222 new impact craters at least 10 meters in width. They also found 47,000 new splatter-like changes or “splotches” in reflectance on the lunar surface – changes that are the result of dust and rock aftershocks that follow the initial crater-forming impact.

“That’s unique to the moon. That’s forming from the primary impact throwing out this ejecta, and that’s what makes these images really unique,” the study author told New Scientist. He added that the largest new crater was 43 meters in diameter and the smallest were 10 meters in diameter (which is the smallest that can be detected using the LRO’s instruments).

Based on these observations, the researchers now believe that the top inch of the moon’s surface layer changes once every 80,000 years, not once every million years as previously believed, said Engadget. While such activity would not pose a threat to lunar settlers, it could change how they date samples collected by satellites and could impact any future plans to mine the moon.

The findings also suggest that the moon is hit by meteorites more frequently than researchers had previously thought, said Kathleen Mandt from the Southwest Research Institute. “I like it when theories are proven wrong, or exciting new things come up,” she told New Scientist, pointing out that the LRO mission “is starting to show there’s a lot we don’t know about the moon.”

Speyerer told Space.com that he was “excited” that he was able to see the lunar surface “evolve and churn – a process that was believed to take hundreds of thousands to millions of years to occur – in images acquired over the past several years… As the mission continues, the odds increase of finding larger impacts that occur more infrequently on the moon. Such discoveries will enable us to further refine the impact rate and investigate the most important process that shapes planetary bodies across the solar system.”

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Image credit: Thinkstock

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