It comes from Apollo:Ĭlues to how often and how hard the Moon is hit lie in data from four seismometers placed on the Moon by the Apollo 12, 14, 15, and 16 missions during 1969-72. “The Standard Model may not work well for the Moon.”įor lunar purposes, “we need more data,” says Cooke. “Our best estimates come from the ‘Standard Meteoroid Model,’ which NASA uses to evaluate hazards to the space station and the space shuttle.” Problem: The Standard Model is based mainly on Earth-data, e.g., satellite observations of meteoroids hitting Earth’s upper atmosphere and human observations of meteors flitting across the night sky. The truth is, “we really don’t know how many meteoroids hit the Moon every day,” he says.
That’s what Cooke and MSFC colleague Anne Diekmann are trying to find out.
The odds of something precious being hit will go up. “The odds of being hit during such a short time were, again, very low.”īut what about next time? Following the Vision for Space Exploration, NASA is sending astronauts back to the Moon to stay longer and build bigger bases (read: bigger targets) than Apollo astronauts ever did. It helped that the astronauts didn’t stay long: Adding all Apollo missions together, they were on the lunar surface less than two weeks. “If you spread the impacts over so much terrain, the probability of being hit is very low,” says Cooke. The Moon has a surface area roughly equal to the continent of Africa. On the airless Moon, meteoroids hit the ground.Īpollo astronauts were never bothered by these projectiles. And when they hit, they do not disintegrate harmlessly in the atmosphere as most would on Earth. They literally fall out of the sky, in all shapes and sizes, from specks of comet dust to full-blown asteroids, traveling up to a hundred thousand mph. This research was supported by NASA's Office of Planetary Defense under grant NNX14AL15G.“Every day, more than a metric ton of meteoroids hits the Moon,” says Bill Cooke of the Marshall Space Flight Center’s Meteoroid Environment Office. Iron meteoroids are much smaller and denser, and even relatively small ones tend to reach the surface. While this mechanism may protect Earth's inhabitants from small meteoroids, large ones likely won't be bothered by it, he said.
#When a meteoroid strikes the surface of the earth code
This new code allowed the researchers to push air into the meteoroid and let it percolate, which lowered the strength of the meteoroid significantly, even if it had been moderately strong to begin with. Different materials in the cell use their individual identity, which is not appropriate for this kind of calculation." "Most of the computer codes we use for simulating impacts can tolerate multiple materials in a cell, but they average everything together. "I've been looking for something like this for a while," Melosh said. To solve the puzzle, the researchers used a unique computer code that allows both solid material from the meteor body and air to exist in any part of the calculation. The meteoroid weighed around 10,000 tons, but only about 2,000 tons of debris were recovered, which meant something happened in the upper atmosphere that caused it to disintegrate. Minutes later, a shock wave blasted out nearby windows, injuring hundreds of people.
When it entered Earth's atmosphere, it created a bright fire ball. The explosion came as a surprise and brought in energy comparable to a small nuclear weapon. Melosh's team looked to the 2013 Chelyabinsk event, when a meteoroid exploded over Chelyabinsk, Russia, to explain the phenomenon. Researchers knew that meteoroids often blew up before they reach Earth's surface, but they didn't know why. "If the air can move through the passages in the meteorite, it can easily get inside and blow off pieces." "There's a big gradient between high-pressure air in front of the meteor and the vacuum of air behind it," said Jay Melosh, a professor of Earth, Atmospheric and Planetary Sciences at Purdue University and co-author of the paper. When a meteor comes hurtling toward Earth, the high-pressure air in front of it seeps into its pores and cracks, pushing the body of the meteor apart and causing it to explode.
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