Asteroids in our Solar System are abundant; millions upon millions of them orbit the Sun. Their velocities vary, but can range upwards of 160,000 kilometers per hour (100,000 miles per hour). Most of these asteroids pose no threat to us; they are either so tiny or so far away. A fraction of them, however, share orbits similar to Earth’s, or travel in big looping orbits that occasionally cross our path. If they cross near enough, they are considered potentially hazardous. Depending on the size of the object, the resulting impact could release energy akin to hundreds or even thousands of nuclear weapons going off simultaneously.
This level of destruction is hard to conceptualize, and is, thankfully, rare. But rare is not “never.” Humanity has been lucky that it’s never suffered a collision with a truly large asteroid. But luck is not a plan. Just ask the dinosaurs how far luck will carry a species. Eventually, it runs out.
Until very recently, an asteroid discovered to be on a collision path with Earth would have been the end of it, an unavoidable fate to be endured. But since the dawn of the space age, many types of NEO impacts are now preventable, at least in theory. NASA’s successful DART mission in 2022 was the first in-space asteroid deflection test. The test was successful, and data gathered will inform future deflection concepts.
The burgeoning field of planetary defense allows humanity a certain control over its own destiny, but only if these objects are found early enough. A decade or more is necessary to properly design, launch, and alter the course of an asteroid or comet to the degree necessary to avoid a collision.
It is therefore in our best interest to make a thorough catalog of threatening NEOs in our Solar System, to actively seek them out before fate elects to bring one to us.