Asteroids: they’re ancient, rocky, and way cooler than you might think. June 30 is International Asteroid Day, a global event to raise awareness about asteroids and what we’re doing to study them. Here’s why we’re obsessed with them (and why you should be, too).
What are asteroids?
Asteroids are leftover building blocks from the early solar system, orbiting the Sun like planetary time capsules. Most hang out in the main asteroid belt between Mars and Jupiter, but some—called Near-Earth Objects, or NEOs—orbit closer to home. They range in size from 329 miles (530 kilometers) in diameter to less than 33 feet (10 meters) across.
Why do we study them?
Studying asteroids helps us unlock the origins of our solar system.
In 2023, our OSIRIS-REx mission collected a sample from asteroid Bennu that could reveal whether asteroids delivered water and other ingredients for life when they collided with Earth billions of years ago.
Lucy in the sky…with asteroids? Our Lucy mission, which launched in 2021, is named for a fossilized skeleton of a human ancestor, which was in turn named for the Beatles song “Lucy in the Sky with Diamonds.” Lucy is the first mission to explore asteroids that share an orbit around the Sun with Jupiter.
A timelapse of the asteroid Donaldjohanson taken on NASA’s Lucy spacecraft. The images, captured approximately every 2 seconds beginning at 1:50 p.m. EDT April 20, 2025, show a white, irregular, elongated shape rotating slowly. Its surface is covered in small craters and has a rough, uneven texture. The asteroid appears bright against a black background. Credit: NASA/Goddard/SwRI/Johns Hopkins APL
What if an asteroid hits Earth?
NASA’s Planetary Defense Program uses telescopes to keep an eye out for asteroids and other NEOs, in case any get too close for comfort. Although a catastrophic collision is highly unlikely for the next 100 years or more, the telescopes detect smaller objects on a collision course with Earth a few times per year. No need to worry—these objects are just a few feet (meters) in size and cause no damage.
Rock on!
Hungry for more? Check out our asteroid portal for a cosmic crash course, or explore a real-time visualization of every known asteroid and comet classified as an NEO with NASA’s Eyes on Asteroids app.
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