Small Space Rocks with Big Impacts
Comets and asteroids may be tiny, but they’ve made a huge impact on Earth’s story. Formed from the same swirling cloud of gas and dust that created the Sun and planets, these ancient travellers are leftovers from our solar system’s earliest days. They spark meteor showers. They shape planets. They even carry the icy, dusty, rocky stuff that may have helped jump-start life on Earth. Ready to chase them through space and see what they left behind?
Meet the Comets
These “dirty snowballs” are made of frozen gases, dust and rock. They formed far from the Sun in cold, dark regions of the outer solar system.
Most comets roam beyond Neptune in the Kuiper Belt, and even farther away in the Oort Cloud. Packed with trillions of frozen space objects, these faraway places are like cold storage for comets. The comets orbit quietly, unless gravity bumps one of them and sets it on a new journey toward the Sun.
A Comet Glowup
Sometimes gravity nudges a comet into a long, looping orbit that carries it closer to the Sun. As the comet warms, ice turns into gas and surrounds the comet’s core in a glowing cloud called a coma. Dust and gas stream out behind the comet in bright tails, transforming a small, frozen object into a spectacular sight.
When Earth passes through the debris left behind by a comet, spectacular meteor showers streak across the night sky. <intralink to meteor showers>
Meet the Asteroids
Asteroids formed when rock and metal clumped together during our early solar system. Today, most asteroids hang out in a ring around the Sun called the asteroid belt.
The Asteroid Belt
Between Mars and Jupiter is a wide band filled with rocky remnants that never formed a planet. When they tried to stick together, Jupiter’s powerful gravity kept pulling them apart.
Imagine trying to stack blocks on a table while someone keeps pulling it away from you. The pieces would tumble and stay scattered.
Could a Comet or Asteroid Hit Earth?
Tiny fragments shed by comets and asteroids enter Earth’s atmosphere all the time. Most burn up as meteors before reaching the surface. Impacts from comets and asteroids are rare, but they have happened.
The Impact that Changed Our Lives
About 66 million years ago, a large asteroid struck Earth close to the area now known as the Yucatán Peninsula in Mexico. Dust and debris blasted into the atmosphere, blocking sunlight and cooling the planet. Plants struggled to grow. Food chains broke down. Many species, including most of the dinosaurs, became extinct. With the dinosaurs gone, new habitats formed, giving mammals places to grow, adapt and thrive.
How Do Scientists Study Comets and Asteroids
Scientists use powerful telescopes, radar and computer models to track these space travellers. But sometimes, watching from Earth isn’t good enough.
Spacecraft have orbited asteroids, landed on them, and brought samples back to Earth. The Rosetta, Hayabusa and Hayabusa 2 missions revealed how these small objects contain organic molecules, some of the basic building blocks of life. By comparing asteroids to comets, scientists learned that one difference is that asteroids are like delivery trucks, bringing much of Earth’s water to our young planet.
They may be tiny specks in space, but asteroids and comets pack a punch—reshaping and creating the conditions that made life possible.
Diagram showing location of belts in solar system
Anatomy of a comet
<suggested visual> Side-by-side animated comparison cards show how asteroids and comets differ in composition, size, location, and behaviour as they orbit the Sun.