An Explosion from Space - The Science of the Meteor over Massachusetts
- Brandon Holloman
- 8 minutes ago
- 4 min read
On Saturday, May 30th, at 2:06 p.m. EDT, people across New England reported hearing two consecutive explosions strong enough to rattle buildings. The source was actually a meteor—a rock falling from outer space.
The reports were centered around the border of New Hampshire and Massachusetts, north of Boston, where the meteor entered the atmosphere. Once it descended to an altitude of 31 miles above sea level, the meteor underwent an air burst explosion, causing the sound heard and the shock wave felt. People throughout the area assumed it was an earthquake they were feeling and reported it as such.
Space Rocks and Shooting Stars
But what happened? Our local Solar System is actually filled with rocks, called asteroids. The smaller the asteroid, the more common it is. If one of these rocks gets too close to Earth and is pulled in by its gravity, then the asteroid will begin its fall towards the surface. Once it enters the Earth’s atmosphere, we now refer to it as a meteor, instead of an asteroid.
The Earth’s atmosphere is one of our primary defenses against impacts from space rocks. As the rock falls down to Earth at breakneck velocities—this one at 42,000 mph—the compression of the air in front of the meteor causes the rock to heat up and burn away. During the night, we see this falling, burning rock as shooting stars. The average shooting star is caused by a meteor about the size of a grain of sand, and therefore they burn up quickly with little fuss.
Fireballs and Explosions
The New England meteor was far larger. Meteors this large are often called fireballs, as when seen at night, they’ll look like a fireball dashing across the sky with enough light to illuminate the surroundings. More officially, they are known as bolides. Estimates put it at about 5 feet in diameter and weighing approximately 6 tons. This larger size allows it to survive deeper into the atmosphere. But even this larger size wasn’t enough to fully protect it.
As a meteor falls, there’s a lot of pressure put on it simply from the act of moving so fast through the air. As it plummets down, the air in front of it is unable to move out of the way fast enough, creating a massive spike in pressure. Meanwhile, a vacuum is created behind the meteor, due to the air being forced down in front of it. This creates a massive pressure differential between the top and bottom of the rock. For medium-sized meteors like this, that pressure differential can eventually wreck the structural integrity of the rock and cause it to undergo a catastrophic air burst, where the meteor fragments apart spectacularly and creates a shock wave.
NASA has calculated that this meteor exploded with the force of 300 tons of TNT. For reference, that’s nearly 30 times more powerful than the strongest non-nuclear bomb in the United States arsenal. In just the second it took to explode, this meteor unleashed enough energy to power the average American household for 35 years, or to power over 12,000 homes for a day.
This explosion may sound like it should cause far more damage than it did, but once again the Earth’s atmosphere protects us. The 30 plus miles of air between the explosion and the ground was enough to dampen it to the point where no damage was caused.
But witnesses reported hearing two explosions. The air burst was actually the second. The first was the sonic boom caused by the meteor falling faster than the speed of sound.
Many fragments remaining from meteors of this size burn up entirely before they hit the ground. Any that didn’t likely ended up in the ocean, somewhere in Cape Cod Bay. The ocean is our secondary defense against impacts. After all, most of the surface of Earth is covered by water, so any meteor that does make it through the atmosphere will likely be landing in the ocean, where the water can harmlessly absorb the remaining energy.
Origin
According to NASA, study of the object’s trajectory have confirmed that it was a lone asteroidal fragment, a piece that broke apart from a larger asteroid long ago due to collisions with other asteroids, and was not a part of any meteor shower. They also confirmed that it was not any kind of man-made debris, which can fall to Earth and create a similar fireball.
On average, meteors the size of this one actually enter Earth’s atmosphere every ten days, with a total of 35 to 40 a year. However, most of these occur well away from populations, such as over oceans and deserts, so they go unnoticed. The actual rare event here was having such a large meteor fall over a populated area on a Saturday afternoon.