Every day, more than a hundred tons of dust and sand-sized material hits the Earth’s atmosphere. This causes the streaks of light we call meteors. But there are bigger objects out there: asteroids and comets. If we work together and properly utilize our space programs, then we will be able to prevent an asteroid impact when the time comes.
Every day, more than a hundred tons of dust and sand-sized material hits the Earth's atmosphere. This causes the streaks of light we call meteors. But there are bigger objects out there. Asteroids and comets. The asteroids and comets that come near Earth's orbit are called near-Earth objects, or NEOs. Big asteroids do not hit Earth very often, but they do hit.
In 2013, an asteroid the size of a house exploded in the atmosphere above Chelyabinsk, Russia causing a shockwave that shattered windows and injured more than a thousand people. In 1908 a 40-meter asteroid exploded in the atmosphere above Siberia. It leveled part of a forest. Trees were knocked down in an area bigger than the city of Los Angeles. 50,000 years ago, a 50-meter asteroid hit in what is now Arizona. It left this giant hole in the ground a kilometer wide. And of course, 65 million years ago a city-sized asteroid hit what is now Mexico. That impact led to the extinction of 70% of all species on Earth including the ancient dinosaurs.
So, yes, asteroids do hit Earth, but they don't hit often, and big ones don't hit as often as small ones. So we don't need to panic, but we do need to do something about it. An impact from space is the only large scale natural disaster we can prevent if we properly utilize our space programs.
The first step to preventing an asteroid impact is to find the dangerous asteroids. We have to know what's out there. We have found nearly 30,000 near-Earth asteroids but there are predicted to be as many as a million that could cause damage if they hit the Earth. So how do we find them? Ground and space telescopes watch the skies and look for tiny dots that move relative to the background stars.
Once discovered, we have to track an asteroid to be able to know if it's going to hit the Earth. Astronomers around the world take picture after picture of these tiny dots. Eventually, the orbital path begins to reveal itself. Then we can predict its orbital path over the next several decades, compare it to Earth's orbit, and determine if the asteroid is on a collision course with our planet. It requires lots of observations over days and weeks and months to predict its orbit and figure out if it will hit Earth.
Next, we need to characterize the NEOs. Just like rocks on Earth, asteroids come in a variety of sizes, shapes, spin rates, compositions, and densities ranging from loose collections of rubble to solid metal. This step may also reveal if what originally looked like one asteroid is actually two, a binary pair. Knowing all these characteristics of asteroids will be crucial when we try to stop an asteroid from hitting Earth.
If a big asteroid is found to be on a collision course with Earth we need to deflect it. This means we change the asteroid’s orbit enough to make it miss Earth. The more warning time we have, the more options we have. There are a variety of deflection techniques that could save Earth from an incoming asteroid. They range from using a large spacecraft's gravity to pull the asteroid off course, to sending up a kinetic impactor to slam into the asteroid, or even using nuclear detonations. But all of these deflection techniques still need more study and work so they're ready to use when we need them.
And no matter which technique ends up being needed many space agencies and nations around the world are going to have to work together to make it happen. Defending the Earth is an international issue that requires international coordination. From policymakers to disaster management agencies to the general public we should all understand the asteroid threat and its potential to be prevented.
If we take these five steps: Find, Track, Characterize, Deflect, Coordinate & Educate, then we will be able to prevent an asteroid impact when the time comes.