A new simulation based on the 2013 Chelyabinsk meteor suggests that air penetrating through cracks can lead to meteors exploding from the inside out.
The research, published in Meteoritics & Planetary Science, looked at the interactions between a rocky meteor falling through the atmosphere and the air surrounding it. As the space rock hurls down towards the ground, it creates a pressurized air bubble in front and a vacuum in its wake. The pressurized air can pass through the rock's porous structure, attracted by the vacuum, which ends up cracking the meteor up.
The traditional view of meteor fragmentation suggests frictions are the main culprit behind a meteor breaking up. Obviously, a huge amount of heat is released as a meteor falls to the ground. The heat quickly chips away at the meteor, but the scientists pointed out that the porosity of the rock also matters in terms of how it falls to pieces.
“There’s more going on than what had been thought before,” said co-author Jay Melosh, from Purdue University, in a statement. “Bottom line is that the atmosphere is a better screen against small impacts than we had thought.”
Meteors are often just lumps of rubble, so air going through them is nothing surprising, but it has been difficult to take that into account in previous simulations. The standard approach uses computer codes employed to describe spacecraft re-entry. However, in the new approach, the scientists used software that models nuclear reactor explosions, allowing them to better simulate the meteor's loose composition.
The researchers wanted to better understand how the Chelyabinsk event happened. On February 15, 2013, a 20-meter (65-foot) bolide exploded over 29.7 kilometers (18.5 miles) above the Urals in southern Russia. The footage of the event quickly went viral, as the meteor burned through the atmosphere. While it was mostly destroyed, several fragments that didn’t burn through the atmosphere managed to reach the ground and were later collected.
NASA estimates 44,000 kilograms (97,000 pounds) of meteoritic matter lands on Earth every day, most of it as micrometeorites.
This new research will be presented this week at the 2017 American Geophysical Union Fall Meeting in New Orleans.