Meteoroids, Meteors, and Meteorites

Meteoroids are the “space rocks”, the objects in space that range in size from dust grains to small asteroids. The meteoroids that enter a planet’s atmosphere at a high speed and then burn up are called meteors, or “shooting stars.” If a meteoroid survives its trip through the atmosphere and hits the ground, it’s referred to as a meteorite. 

Some meteoroids are pieces of larger space rocks while others come from asteroids, the moon, and other planets. Meteoroids can be rocky, metallic, or a combination of rock and metal. 

Sometimes meteors can appear to be brighter than Venus; this is when they are referred to as “fireballs”. On any given night, several meteors can usually be seen, but when there are more meteors, it’s called a meteor shower. Some meteor showers can occur annually or at regular intervals as the Earth passes through the trails of debris that are left by comets, or in a few cases, asteroids. Meteor showers are typically named after a star or constellation that’s close to where the meteors seem to originate in the sky. One famous meteor shower is the Perseids which peak around August 12th every year. Each meteor in this shower is a small piece of the Swift-Tuttle comet. Most of the debris left by comets is between the size of a grain and a pea, and they burn up in the atmosphere before they can reach the ground. Most space rocks that are smaller than a football field will break apart in Earth’s atmosphere. Traveling at tens of thousands of miles per hour causes the meteor to disintegrate as the pressure exceeds the strength of the rock. This results in the bright flare we see in the sky. Usually, less than 5% of the original rock makes it to the ground.

The size of meteorites typically ranges between the size of a pebble and a fist. Compared to other places, it is easier to identify meteorites in deserts. While they may look similar to Earth rocks, meteorites usually have a burned exterior that can look shiny. This fusion crust is formed when the meteorite’s outer surface melts during its trip through the atmosphere. By studying meteorites, we can learn about the early conditions and processes in the solar system’s history. Some examples are the age and composition of different planetary building blocks, and the temperatures reached at the surfaces and interiors of asteroids. These meteorites represent some of the original and diverse materials that formed planets billions of years ago. More than 50,000 meteorites have been found on Earth and 99.8% come from asteroids. The remaining 0.2% is split between meteorites from the moon and from Mars. 

Sources: solarsystem.nasa.gov