Dec. 11 (UPI) -- Why do most meteors explode before they reach Earth?
The atmosphere burns up most of the rock fragments that collide with Earth's path, but it's not just friction that neutralizes the threat of small meteors. New research suggests high-pressure air forces its way inside the porous space rocks and explodes them from the inside.
"There's a big gradient between high-pressure air in front of the meteor and the vacuum of air behind it," Jay Melosh, a professor of planetary science at Purdue University, said in a news release. "If the air can move through the passages in the meteorite, it can easily get inside and blow off pieces."
Researchers knew many meteors explode in Earth's atmosphere, but they're weren't sure why. Simulations modeling the interaction between high-pressure air and the porous rock offered the answer.
"There's more going on than what had been thought before," Melosh said. "Bottom line is that the atmosphere is a better screen against small impacts than we had thought."
Meteors feature pores and cracks, but until now, scientists hadn't considered the role theses features play in dictating the space rocks' interactions with Earth's atmosphere.
Melosh and his colleagues first considered the air percolation mechanism while studying the 2013 Chelyabinsk event. The Chelyabinsk meteor exploded 19 miles above Russia's Chelyabinsk Oblast region with the force of 500,000 tons of TNT, generating a shockwave that broke thousands of windows and sent hundreds of people to the hospital.
For the latest study, researchers used computers at the Los Alamos National Laboratory to simulate the passage of high-pressure air through the fissures and microcavities inside the loose conglomerate composition of meteors. The findings -- published this week in the journal Meteoritics & Planetary Science -- showed the high-pressure air can quickly rip apart the meteor from the inside-out, creating an explosion and disintegrating the meteor in the upper atmosphere before it has a chance to reach Earth's surface.
Melosh presented the research on Monday at the 2017 American Geophysical Union Fall Meeting in New Orleans.