Chasing asteroids: Dual missions sniff out clues to solar system's past
It was a normal Friday morning in the industrial city of Chelyabinsk, Russia. Adults were on their way to work, and children were in school. But that ordinary day was about to become extraordinary.
Suddenly, a fireball shot across the clear morning sky leaving a thick trail of smoke, accompanied by the sound of a huge explosion. The shock wave knocked people over, shattered glass, and collapsed a factory roof. As many as 1,200 people were injured. A global network of infrasound sensors designed to pick up nuclear explosions calculated that the boom was 30 to 40 times more powerful than the atomic bomb the United States dropped on Hiroshima, Japan, during World War II.
But this event on Feb. 15, 2013, wasn’t a declaration of war. It was simply an asteroid that crossed paths with Earth on its travels around the sun.
As the space rock hurtled toward Russia, the pressure of Earth’s atmosphere was too much for it. The asteroid exploded over Chelyabinsk. Much of the material burned up in the atmosphere, creating a spectacular fireball. The remaining chunks fell to Earth, the largest of which plunged through a thick layer of ice into a lake.
The Chelyabinsk meteor stirred up fear in people around the globe. Nobody died this time, but what if a bigger asteroid hits Earth over, say, New York or London? Is humanity in for an asteroid-driven Armageddon?
While this terror periodically grips people around the world – and engages Hollywood screenwriters – it is hardly an imminent threat. True, an asteroid the size of a car plunges toward Earth about once a year, but most of the rock burns up in the atmosphere.
Scientists consider the chance of
