While flying just a few thousand miles above the moon on April 6, Artemis II astronauts reported seeing a handful of bright, fleeting flashes of light on the lunar surface, leaving mission scientists on Earth buzzing with excitement.
The excitement comes with good reason for scientists planning future lunar missions: These brief flashes, caused by tiny meteorites striking the moon, help researchers track when and where impacts occur. Such data can improve scientists’ understanding of the risks these impacts pose to long-term infrastructure and a sustained human presence on the moon.
“One has to plan for the less-frequent, more hazardous events,” David Kring, a scientist at the Lunar and Planetary Institute in Houston, told Live Science. Back in 2016, Kring proposed the idea that future moon explorers should try to detect such impact flashes on the lunar far side. “The lunar flashes the Artemis II astronauts observed remind us to plan for that contingency,” Houston said.
“Audible screams of delight”
The Artemis II crew spotted the flashes during their historic flyby around the lunar far side, when the moon briefly blocked the sun and created a total solar eclipse that lasted nearly an hour and left the far side in complete darkness. Against this stark backdrop, the crew observed at least four millisecond-long flashes on the lunar surface, and possibly as many as six, commander Reid Wiseman radioed to mission control in Houston.
“There was a little bit of giddiness,” Wiseman said through the mission livestream, reporting a fresh flash spotted by crewmate Jeremy Hansen even as he relayed earlier observations. “It was definitely impact flashes on the moon.”
“Incredible news, Reid,” science officer Kelsey Young responded from mission control, raising her hand to her forehead in awe. There were “audible screams of delight” from scientists as the observations came in, Young told reporters at an April 7 news conference.
Scientists on Earth have already begun working to match the crew’s observations with data from the moon-orbiting Lunar Reconnaissance Orbiter, with the goal of refining existing models of how frequently such impacts occur. To do so, researchers plan to combine astronaut reports with orbital data to extract key measurable details about the flashes, including their brightness, the meteorites’ masses, and whether the events created fresh craters on the lunar surface.
Meteorites and moonquakes
A less-visible consequence of these impacts is the shock waves that ripple through the moon. Such “moonquakes,” when recorded by seismometers, can reveal how energetic and potentially damaging each strike was.
Like the Artemis II crew, Apollo astronauts reported seeing a handful of impact flashes, but most occurred too far from the seismometers operating at the time to be detected, a recent analysis found. Even so, Apollo-era instruments recorded about 1,700 impact-related moonquakes. Some were powerful enough to “cause boulders to roll downslope,” Kring said, while the largest could “cause crater and canyon walls to collapse,” which would pose risks to future lunar habitats.
Currently, however, no active seismometers are operating on the moon to support the Artemis era.
“Hopefully the first landed Artemis mission will change that,” Nick Schmerr, a geophysicist at the University of Maryland who co-authored the analysis cross-referencing Apollo-era flashes with moonquakes, told Live Science.
Seismometers are among the instruments NASA plans to deploy through a fleet of early robotic missions ahead of crewed landings planned for 2028 and beyond. By combining astronaut observations with data from seismometers, telescopes and orbiters, scientists could precisely locate impact events and track their effects.
“We’d certainly want to know about any nearby impacts for a moon base, especially if they hit near crucial infrastructure,” said Schmerr, who is also the deputy principal investigator for a planned seismometer known as the Lunar Environmental Monitoring Station for Artemis (LEMS). “The more observations of a particular flash from different observers, the better.”
Over time, such observations could help scientists refine estimates of how much asteroid and comet debris is striking the moon, Kring said. Larger impacts can excavate material from deep beneath the surface to reveal lunar geology that would be inaccessible otherwise. If such events occur near the polar regions, Kring added, they may even expose ice that NASA and other space agencies suspect is present and could someday be harnessed for life support and rocket fuel.
Looking further ahead, analyzing moon samples ferried to Earth from Artemis landing sites could allow researchers to identify the types of meteorites striking the moon and track how their composition has shifted over roughly 4 billion years of solar system history, Kring said. Ultimately, though, these impacts matter “because they produce and modify the lunar soil that future Artemis astronauts will walk on,” he added.
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