So where has this potentially devastating space rock come from? Well, it’s thought that asteroids were forged in the same high energy crucible that gave birth to our solar system. These rocky bodies range in size from small pebbles to enormous hunks of stone measuring hundreds of miles across. Their creation – along with that of the Sun, planets and moons – came about approximately 4.6 billion years ago when an enormous molecular cloud containing dust and gas collapsed in on itself.
Now, small pieces of asteroids and other space rocks sometimes fall to Earth. And although most such bodies burn up in the atmosphere as “shooting stars,” occasionally – around ten times a year – a small piece of rock makes it to the surface. Known as meteorites, these rocky fragments often leave a small impact crater. But unless you have the cosmic misfortune of being hit by one of these falling space rocks, they pose no serious threat to human life.
An asteroid the size of Bennu is another matter, though. You see, the impact of such a large space rock would unleash kinetic energy equivalent to tens of thousands of atomic bombs. And the subsequent shockwaves would cause earthquakes and tsunamis. Meanwhile, the resulting dust cloud would probably cool the planet for hundreds of years – thereby devastating Earth’s ecology.