The asteroid Dimorphos is more than 500 feet wide. 

NASA/Johns Hopkins APL (Dimorphos); Detlev van Ravenswaay/Science Source (asteroids); World Perspectives/Getty Images (comets); ANDRZEJ WOJCICKI/Science Photo Library RF/Getty Images (meteors)

Collision Course

Crashing a spacecraft into an asteroid might sound like a mistake. But NASA, the U.S. space agency, plans to do just that later this year.

An unmanned spacecraft called DART blasted off from California last November. Early next fall, it’s expected to reach an asteroid called Dimorphos. DART will slam into the space rock at 15,000 miles per hour. The goal is to slow the asteroid’s speed and change its path. 

Experts say Dimorphos poses no danger to us. The closest it has come to Earth is about 4.5 million miles. So why destroy DART? The purpose of the test is to show that scientists can change the course of an asteroid that might someday be a threat to Earth.

Scientists are tracking more than a million asteroids orbiting the sun. Luckily, most of them fly harmlessly by our planet.

Thousands of small space rocks enter Earth’s atmosphere each year. But most burn up before reaching the ground. Others fall into the ocean.

But a huge asteroid hitting Earth isn’t out of the question. An asteroid the size of a small city smashed into part of present-day Mexico about 65 million years ago. 

Scientists say there’s little threat of anything like that happening in the next 100 years. But DART will help them prepare, just in case.