October 12, 2016 | David F. Coppedge

Moon Just Got 100-fold Younger

New study of craters shows that moon’s surface gets churned every 81,000 years, not every million years.

I like it when theories are proven wrong, or exciting new things come up,” remarked Kathleen Mandt of Southwest Research Institute, quoted by New Scientist. That’s how to put a cheerful spin on an orders-of-magnitude correction. “The Lunar Reconnaissance Orbiter is starting to show there’s a lot we don’t know about the moon.” Data from LRO are showing a much higher influx of meteorites to the moon’s surface, implying that future astronauts stand a bigger-than-trivial chance of being in danger from flying rocks and dust. The data raise questions about the age of the lunar surface.

The revised number of craters suggests the moon is pummeled by space rocks much more frequently than predicted, says Kathleen Mandt of the Southwest Research Institute in San Antonio, Texas. It also suggests that the soil on the lunar surface is turning over so often that materials like water molecules could escape into space sooner than previously thought. That could have important implications for researchers trying to date rocks on the moon, or future initiatives hoping to mine resources out of the moon.

Space.com says of the “Impact!” of the finding, “New Moon Craters Are Appearing Faster Than Thought.” Part of the new estimate comes from crater counts by LRO, including a whopping 222 new craters appearing just in the last 7 years, says Alexandra Witze in Nature. The other part comes from estimates of secondary craters formed from each new impact.

The scientists also found broad zones around these new craters that they interpreted as the remains of jets of debris following impacts. They estimated this secondary cratering process is churning the top 0.8 inches (2 centimeters) of lunar dirt, or regolith, across the entire lunar surface more than 100 times faster than thought.

Realization of widespread secondary cratering upset the crater-count dating method a decade ago (9/25/07), rendering the method essentially unreliable (5/22/12). Even if a future moon colonist avoids a direct hit, he or she could be at risk of debris from a distant impact if rocks and dust fly in all directions with no atmosphere to slow them down. Picture yourself working at a futuristic moon base stepping outside to watch the Earthrise:

“For example, we found an 18-meter (59-foot) impact crater that formed on March 17, 2013, and it produced over 250 secondary impacts, some of which were at least 30 kilometers (18.6 miles) away,” Speyerer said. “Future lunar bases and surface assets will have to be designed to withstand up to 500 meter per second (1,120 mph) impacts of small particles.

PhysOrg says the meteoritic rain is so heavy, it gives the moon a facelift every 81,000 years, overturning the top two centimeters of lunar dust. Some impactors were big. The astronomers found 33% more craters than expected with diameters at least ten meters.

None of the articles asks the obvious question: what does this mean over the assumed lifetime of the moon? If the moon really formed 4.5 billion years ago, as secular planetary scientists believe, that would be 5,555 facelifts. (It should be noted that the 81,000-year estimate uses models that assume the billions-of-years age of the moon. All they can really observe is the current impact rate. The new observations, however, imply a faster production rate than the favored model assumes.)

Another consequence of the study affects all the planets and moons of the solar system. Does the impact rate need to be revised upward everywhere else? Are primary and secondary craters occurring much more frequently than expected at Mars and the moons of Saturn, or at Pluto? Meteor flux could vary at different radii from the sun. It’s also a factor of gravitational pull. But without a reconnaissance orbiter at each planet or moon, it’s hard to be sure. New craters have been observed at Mars – again, at a higher rate than expected (2/13/14).

Earth, with its higher gravity, attracts meteors at an even higher rate, but our atmosphere causes most of them to burn up high in the sky. Meteors are commonly observed by skywatchers. The occasional meteor shower increases the rate when Earth passes through the dust stream of a comet. The rare meteorites (meteors that reach Earth’s surface) are prized by collectors. Some of them come from Mars and other planets, when glancing blows send rocks our way (3/25/08).

The research paper in Nature by Speyerer et al. contains before-and-after photos of impact sites.

The trend in crater-count dating has been up and down: up in the number of impact events and secondaries, down in the method’s credibility. It’s clear that these results were surprising. Despite all those thousands of craters, the moon doesn’t have to be billions of years old.

This paper should stimulate creationists to revisit the moon dust problem. In the Apollo era, all the secular astronomers were astonished at the thinness of the lunar regolith. The Surveyor landers proved that the dust was not meters thick with fine dust as some had predicted. Apollo astronauts found the dust to be so shallow, they could scratch the bedrock with their boots. It seemed that fine dust had not been accumulating for billions of years. When subsequent estimates of dust influx were substantially reduced, many creationists abandoned the moon-dust argument for a young moon.

Perhaps that was premature. This paper shows that impacts send up jets of dust that settle back under ballistic trajectories. If the top two centimeters can be completely “gardened” in just 81,000 years, it seems highly implausible to believe this has happened over 5,000 times. Some creation physicist ought to read the new paper and revisit the implications for age.

 

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