Scientists have figured out why meteoroids explode before hitting the Earth II Why Do Meteoroids Explode in the Atmosphere? II Recent Research Reveals New Information On Meteoroids

Photographer Marat Ahmetvaleev was taking panoramic photos of the winter landscape when he captured this beautiful image of the Chelyabinsk meteoroid as it exploded over Russia in 2013. (Credit: M. Ahmetvaleev/NASA APOD)

On February 15, 2013, a near-Earth asteroid with a diameter of 66 feet (20 meters) entered Earth’s atmosphere traveling at around 40,000 miles per hour (60,0000 km/h).

Within a few seconds, the cosmic projectile detonated 12 miles above the Chelyabinsk region of Russia, releasing as much energy as about 30 Hiroshima atomic bombs. This created a gigantic fireball — known as a superbolide — that caused shock waves to propagate outward for dozens of miles, damaging several thousand buildings and injuring 1,500 people.

Though the progenitor of the explosion had an initial mass of over 10,000 metric tons, only about 0.1 percent of that mass is believed to have reached the ground, indicating that something in the upper atmosphere not only caused the rock to explode, but also caused it to disintegrate much more than expected.

Monday, a team of researchers published a study in Meteoritics & Planetary Science that proposes a new and previously overlooked mechanism for air penetration in meteoroids, which could help explain the powerful breakup of the Chelyabinsk meteoroid.

According to the paper, as a meteoroid hurtles through Earth’s atmosphere, high-pressure air in the front of the object infiltrates cracks and pores in the rock, which generates a great deal of internal pressure. This pressure is so great that it causes the object to effectively blow up from the inside out, even if the material in the meteoroid is strong enough to resist the intense external atmospheric pressures.

“There’s a big gradient between high-pressure air in front of the meteor and the vacuum of air behind it,” said the study’s co-author Jay Melosh, a professor of Earth, Atmospheric, and Planetary Sciences at Purdue University, in a press release. “If the air can move through the passages in the meteorite, it can easily get inside and blow off pieces.

According to the paper, “This process of pressure internalization, new to meteoritic studies, would not have been recognized without a two-material fluid dynamics code.” This unique computer code allowed researchers to generate models that let both air and solid material coexist in any part of the calculation.

“I’ve been looking for something like this for a while,” Melosh said. “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.”

Though this process of air penetration is a very effective way for our atmosphere to shield us from smaller meteoroids, larger and denser ones will likely not be as affected by it. However, the more we can learn about how different meteoritic materials explode, the more prepared we can be for the next Chelyabinsk

Meteoroids

Jay Melosh has discovered why exactly meteoroids sometimes explode when they enter the earth’s atmosphere. Back in 2013, a meteoroid exploded over Chelyabinsk, injuring hundreds of people with a blast equivalent to a small nuclear weapon.

The meteoroid, weighing in at around 10000 tons, shattered nearby windows in a gigantic ball of fire, but left only 2000 tons of debris. This meant that something had occurred in Earth’s upper atmosphere that caused it to shrink in size.

Melosh, a professor at Purdue University and coauthor of the recently published paper, explained that when a meteoroid enters the Earth’s atmosphere, high-pressure air enters pores in its surface and pushes the body apart, causing an explosion.

“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,” said Melosh.

While scientists have known for a while now that meteoroids explode upon entering the atmosphere, this is the first time that we’ve understood why. Melosh and his team employed a novel technique to the events that occurred in Chelyabinsk, and used their findings to provide evidence of a process we previously didn’t understand.

Unlocking the Meteoroid’s Secrets

In order to arrive at this conclusion, researchers on the study used a unique compilation of computer code that accounts for both solid material from the meteor as well as air existing at any point during the calculation. “Most of the computer codes [they] use[d] 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.”

This new collection of code allowed researchers to model the explosion, pushing air into the meteoroid and noting that the strength of the meteoroid was lowered significantly. This knowledge helps us understand why some meteoroids are not a significant threat to us here on earth.

Melosh warns, however, that not all meteoroids will be affected by air in such a fashion. Small meteoroids, especially those made of dense materials like iron, can reach Earth’s surface and cause significant damage.

While the practical implications of such knowledge are not quite understood, the increased understanding of why exactly some meteoroids seem to be so much smaller upon arriving at earth’s surface advances our knowledge of space debris that can affect us on our planet’s surface. While there might not yet be a way to avoid situations like the many injuries in the 2013 Chelyabinsk impact, it’s nice to know at least why these blasts occur. Further research may prepare us to deal with the impact of such meteoroids, but until then, it’s a great breakthrough in the field of planetary science — and a perfect example of the benefits of computer science in understanding the universe in which we live.