Earth’s Atmospheric Shield

In 2013 a 10,000-ton 60-foot (20 m) wide asteroid entered the Earth’s atmospheric shield and exploded over Chelyabinsk, Russia. The explosion occurred 18 miles (29 km) above the Earth emitting a shock wave equivalent to 10 Hiroshima bombs.

A team led by Dr. Jay Melosh of Purdue University has extensively studied what controls how much damage a rock from space can cause. Dr. Melosh’s research was funded by NASA’s Office of Planetary Defense, and some interesting facts have come from the research. According to the study, Hollywood disaster movies aren’t even close to being realistic. Dr. Melosh says “Realistic stuff doesn’t make a good story. Hollywood usually manages to get it wrong.”

Meteoroids are hunks of rock that come in all shapes and sizes and with different amounts of porousness. As a rock enters the atmosphere, air pressure builds up in front of it, and a vacuum develops behind it. For most porous rocks, the air will rush into the rock and blow off pieces, like an air hose blowing in a bucket of sand. The design of the Earth’s atmosphere is what causes the break-up of the meteoroids. It is only if they are too big to blow apart that they hit the Earth leaving a crater such as Meteor Crater in Arizona.

The article about Dr. Melosh’s work in the Herald Bulletin says that Earth’s atmospheric shield is better than we thought. Modern astronomy continues to find design features of the universe and the Earth that allow life to exist on this planet. This is another example of a design feature that makes it so that we don’t have to walk around looking up to dodge an incoming celestial missile.
–John N. Clayton © 2018