Thursday, January 26, 2017

What are....Meteorites, Meteoroids, Meteors, Asteroids, and Comets

I occasionally do a set of blogs called "What are...". Here is the next one in the series.

I was reading a book with my daughter, book 8 of the Magic Tree House series - Midnight on the Moon (her current favorite series of books to read) and I came across this passage that seemed off to me:

The main part I was stuck on was:
"Rocks of all sizes crash into the moon from outer space. These rocks are called meteorites."
From what I could remember, meteorite is a term specifically reserved for rocks that crash into Earth. But did it apply to rocks that crashed into the moon (or other planets for that matter) as well? Looking into it, no. This was incorrect. Meteorites are rocks that specifically have traveled through our atmosphere and crashed into the Earth.

So what would be an object that crashed into the moon?  Turns out that NASA scientists just refer to them as meteoroids, as can be seen in this story - A Meteoroid Hits the Moon.

So what are the differences between a meteor, meteorite, meteoroid, asteroid, and comet?

Meteoroid - These are chunks of rock that are floating in space that are smaller than a kilometer in diameter (

Meteor - This is just the flash of light, a shooting star, that you see in the night sky as a meteoroid falls through the atmosphere and starts to burn up. This is not the physical object that is falling (

Meteorite - A meteorite is a meteoroid that has survived entry through the Earth's atmosphere and has crash landed on the surface of the Earth ( This term seems to be exclusive to rocks found on Earth, since terms like "Martian meteorite" or "lunar meteorite" are for meteorites found on Earth that originated from Mars or the moon respectively.

Comet - A comet is a body of ice, rock, and organic compounds that can be up to several miles in diameter. "Comets are thought to originate from a region beyond the orbits of the outermost planets. Scientists believe that gravitational perturbations periodically jar comets out of this population, setting these "dirty snowballs" on orbital courses that bring them closer to the Sun. Some, called long-period comets, are in elliptical orbits of the Sun that take them far out beyond the planets and back. Others, called short-period comets, travel in shorter orbits nearer the Sun" (

Asteroid - "Most asteroids are made of rock, but some are composed of metal, mostly nickel and iron. They range in size from small boulders to objects that are hundreds of miles in diameter. A small portion of the asteroid population may be burned-out comets whose ices have evaporated away and been blown off into space. Almost all asteroids are part of the Main Asteroid Belt, with orbits in the vast region of space between Mars and Jupiter. In space, a large rocky body in orbit about the Sun is referred to as an asteroid or minor planet whereas much smaller particles in orbit about the Sun are referred to as meteoroids" (

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