Understanding the difference between meteoroids, meteors, meteorites and comets can be difficult, especially as the first three sound so similar. They are in fact linked, via their life cycle, and also by the Greek translation of the word Meteron, which means a phenomenon in the sky.
# Meteoroids
Floating freely in our solar system are chunks of stone and metal. These meteoroids may be tiny, like a grain of sand, or far larger, resembling a boulder.
# Meteor
Meteors were once meteorioids, which, having come into contact with the gravitational pull of a moon or planet, ceased to be labelled as meteoroids anymore. A meteor will head directly towards the planet or moon which has engaged it, and may be referred to as a shooting, or falling star, which of course, it isn’t really. However, because it’s so bright it can look just like a star to observers on Earth. The so called tail of a shooting star is generally made up from smoke, as well as light, and hisses as it zooms along.
# Meteorite
A meteor becomes a meteorite when it goes so far as to actually strike the surface of the moon or planet which its attracted to, due to experiencing its gravitational pull. Meteorites are far rarer than meteors, as most of them don’t get as far as reaching an actual planet or moon, as they burn up beforehand.
# Comet
Comets, unlike meteoroids, meteors, and meteorites, consist of frozen gases, intermingled with grains of sand like particles and rocks, and can be found in elliptical orbits around the sun. Scientists think that the material they’re made from is debri, left over when planets were formed. They can range from 750 meters to 12 miles, which is small in comparison to a planet. However, comets can emit a material which is far larger than a planet, known as a coma when they get close enough to the sun.
Comets are said to be formed from the passing tails of meteoroids, which is why the four celestial bodies are often grouped together in descriptions. The phenomenon in the sky continue to fascinate scientists, who are still learning more about them, and using this knowledge to find out more about how the universe and all which reside within are formed. To observers, meteoroids, meteors, meteorites and comets will always be inspirational reminders of how small the Earth really is amongst a sea of amazing miracles.
Sources
http://www.brighthub.com/science/space/articles/66254.aspx
http://www.solarviews.com/eng/comet/whatis.htm
http://www.solarviews.com/eng/meteor.htm
http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/1-asteroid-planetiod-meteoroid.html
