Northern Arizona astronomy: meteoroids, meteors and meteorites

So, what is the difference between meteoroids, meteors and meteorites?

Meteoroids are small asteroids or rocks in space. Meteors are the bright streaks that we see in the night sky from material burning up because of friction while passing through atmosphere as they fall to Earth. Most are actually no larger than a grain of sand that usually never reaches the ground. Meteorites are the rocks that have fallen from space and were large enough to have survived the fiery passage through the atmosphere to successfully land on Earth. So, in summary: a rock in space is a meteoroid, one falling to Earth is a meteor and one found on Earth is a meteorite.

Most meteorites are fragments of small planetesimals (meteoroids and asteroids) that were shattered by collisions early in the history of the solar system. Most of these remnants now form the asteroid belt. Fragments of these asteroids may be knocked out of their orbits by collisions, and if their paths should cross Earth’s orbit, they may eventually pass into our atmosphere as meteors, or if large enough, as bolides (extremely bright meteors) flaring through the evening sky. Though most meteorites are suspected to have come from the asteroid belt, a few rare ones have been found to be fragments of rock originating from the moon, mars or the asteroid Vesta, which were ejected into space by the impact of other meteoroids or asteroids striking these bodies. These meteorites have been identified by their chemical make-up and matched to their respective celestial body, all of which differ from rocks that are of Earth origin.

There are three basic types of meteorites: stony, iron and stony-iron. Though the stony meteorites are the most common in space, after falling to Earth they blend in more against our planet’s terrain and are difficult to find. Irons are almost entirely composed of nickel-iron, which stands out more, and are discovered in greater numbers. However, there is one type of stony meteorite, called carbonaceous chondrites, which have gained a lot of scientific scrutiny because they contain complex molecular materials, including amino acids that are indicative of the beginnings of life.

Scientists have determined that the original inhabitants of Earth were single-celled organisms we now call bacteria which are extremely robust, having survived the most hostile of conditions the Earth has ever experienced in its history. They have existed for almost 4 billion years, and are still found today just about everywhere, in the harshest of environments, such as in boiling hot geothermal springs, deep below the frozen Antarctic, miles deep beneath the highly pressurized crust of the Earth and even floating high up in the atmosphere.

Meteorite hunting and collecting has become an interesting hobby. If you want to find meteorites, you have a few choices. You can be very lucky and observe one falling. You can travel to Antarctica, where dark rocky or metallic meteorites, which have fallen from space, are easy to spot against the white snow. Or, you can wander around the deserts of Earth, where they are also relatively easy to spot against the tan terrain. Arizona, being mostly desert, has given up a large number of both stony and iron meteorites over the years to both scientists and collectors.


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