Meteoroids are objects in space that are typically made of dust, rocks, or metal. They can range from small grains of dust to small asteroids. They're essentially space rocks floating out in space.

When meteoroids get near Earth, gravity pulls them into our atmosphere, where they begin to burn. That burning is the light we see in our skies. In this state, meteoroids are called meteors. If a meteor passes through the atmosphere without completely burning and it lands somewhere on Earth, it is then called a meteorite.

NASA estimates that 48.5 tons of meteoric material fall to Earth each day. Most meteors are completely burned in our atmosphere. The best place to find the ones that reach Earth's surface is the desert or an icy place like Antarctica. They're easier to find in these places because by the time they land on Earth, meteorites look similar to any rock you'd find in your yard. It's difficult to distinguish them from rocks that naturally occur on Earth.

Meteoroids can originate from comets, asteroids, moons, or planets. The most common source of meteor showers is comets. This module focuses on comets.

Comets are made mostly of ice. They're embedded with some dust, rock, and metals. Comets have elliptical orbits around our sun. So sometimes they are nearer to the sun than other times. When a comet is near the sun, it often begins to melt. As it melts, some of the dust, rock, and metal dislodge from the comet and remain in space at that location.

When Earth nears a location where a comet has shed debris, that debris can enter our atmosphere and cause meteor showers. Because some locations in Earth's orbit are more likely to have a lot of comet debris, meteor showers are more common in those locations.

Fun fact: Earth's oceans were likely caused by comets that struck our planet during its formation and melted into water!