It has never really been understood how our atmosphere protects us against meteoroid impacts. It’s well recognized that meteoroids often explode before they reach Earth’s surface; however, researchers were uncertain as to why this happened until now.
Researchers from Purdue University have discovered our atmosphere is a better shield from meteoroids than previously thought. They have found that as a meteor comes hurtling toward Earth, the high-pressure air in front of it is forced into its pores and cracks.
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This force pushes the body of the meteor apart, which causes it to explode. Jay Melosh, a professor of Earth, Atmospheric, and Planetary Sciences, co-author of the paper published in Meteoritics & Planetary Science, explained in a statement:
“There’s a big gradient between high-pressure air in front of the meteor and the vacuum of air behind it.
“If the air can move through the passages in the meteorite, it can easily get inside and blow off pieces.”
Melosh’s team already understood meteoroids often explode before they reached Earth’s surface; however, the question was: “Why?” The researchers turned to the 2013 Chelyabinsk event to explain the phenomenon.
Meteoroids like Chelyabinsk lose most of their mass before hitting the Earth
The Chelyabinsk meteoroid weighed around 12,000-13,000 tons, yet only about 2,000 tons of debris was recovered. This indicates that something happened in the upper atmosphere that caused it to disintegrate.
The explosion over Chelyabinsk, Russia, came without warning and produced energy comparable to that of a small nuclear weapon. As it entered Earth’s atmosphere, it created a bright fireball. Minutes later, a shock wave blasted out nearby windows, injuring just over 1,000 people.
The researchers used a unique computer code that allowed for both solid material from the meteor body and air to exist in any part of the calculation. Melosh explains:
“I’ve been looking for something like this for a while. Most of the computer codes we use for simulating impacts can tolerate multiple materials in a cell, but they average everything together.
“Different materials in the cell use their individual identity, which is not appropriate for this kind of calculation.”
The results of the calculations revealed that air pressure in front of a meteor was so powerful that the air was able to move through the meteorite. This weakened the meteoroid significantly, even if it had been moderately strong to begin with.
While the study indicates Earth’s atmosphere works as a natural barrier against debris and porous meteors, the researchers caution that large ones likely won’t be bothered by it. Iron meteoroids are much smaller and denser, and even relatively small ones tend to reach the surface.