Why Meteoroids Explode Before They Reach Earth

While burning from the friction with Earth's thin air, the supersonic flying space rock exploded 12 to 15 miles above Chelyabinsk. (Image:  Alex Alishevskikh  via   flickr  /  CC BY-SA 2.5)
While burning from the friction with Earth's thin air, the supersonic flying space rock exploded 12 to 15 miles above Chelyabinsk. (Image: Alex Alishevskikh via flickr / CC BY-SA 2.5)

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.

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:

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.

The Chelyabinsk meteoroid weighed around 10,000 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 the 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:

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.

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