Asteroids & Meteoroids

About Meteoroids, Meteors, & Meteorites
Meteorites come from the far reaches of our solar system. Meteorites aren’t always meteorites though. What I mean is this. It’s not called a meteorite when it’s in space. While still in space it’s called a meteoroid.

While in flight through our atmosphere it’s called a meteor. Yes, it’s a meteoroid while falling, and “meteor” part is actually the fiery phenomena produced by the meteoroid falling at tremendous speed through our atmosphere. If a meteoroid strikes Earth and survives both it’s fiery journey, and impact with the ground then it’s called a meteorite.

Meteorites Are found all over our planet and millions of tons of space debris falls on our planet per year. Our planet is actually growing albeit very slowly over time.

How Meteorites End Up On Earth
Meteoroids are floating around out in the space between our planets. Most meteoroids and asteroids come from the asteroid belt that lies between Mars and Jupiter. How they get on Earth is rather by chance. Asteroids are larger celestial bodies usually around 50 meters or more in diameter which float around in the asteroid belt, and from time to time they bump into one another.

Asteroid 2008 TC3

When they do, they not only change direction and get sent of into different orbits around our Sun but they also fragment somewhat into smaller pieces and chunks and these pieces get sent out in all directions.

Some of these meteoroids and asteroids find their way towards the orbit of Earth. If they happen to be crossing our orbital path at the exact moment our planet is then you have a meteor. Most meteors are small grain sized particles, but sometimes they can be much larger.

Asteroid TC3 2008 – October 7th 2008

This was a particularly interesting asteroid/meteoroid because it is the first time in history an asteroid was predicted to impact Earth and then actually hit Earth! Not only did scientists predict it would hit Earth, they predicted when and where and then sent an expedition team and recovered the meteorites.

Scientists discovered the asteroid, calculated it’s trajectory, and predicted the fall area all within a few days time. Recovery took a bit longer because of logistical reasons but this is a perfect example of what happens and how a meteorite ends up on our planet.

Read more about Asteroid 2008 TC3 and the recovery here.

Meteor

About Meteors & Fireballs
Meteors and fireballs are the same but different. Fireballs are the same thing as a meteor, only bigger. Fireballs are much rarer than meteors, and even more rarely seen by humans. Given that 70% of the Earth is covered in water that means that 70% of all meteorites that have struck Earth landed in the Earth’s oceans.

Since the oceans are as desolate a place as you can get, it makes since that most fireballs that occur are never seen. That’s not counting the number of fireballs and meteors over land. Humans only inhabit a small portion of our planet. There are very remote parts on this rock we call home. So remote that any huge fireballs over land in that area would never be seen by human beings.

Take into account that humans live primarily in densely populated areas that’s still not considering the fact that we also live our lives on a schedule. We’re indoors most times and when we are outdoors it’s usually during the day. Meteors and fireballs are not easily seen during the day, and most people are busy with their daily routine anyway to notice a fireball in the sky. Considering all this it’s a wonder we actually see any fireballs and meteors at all, much less recover any meteorites on the ground.

Arizona Desert

Where The Meteorites Are
Meteorites can be found anywhere there is land. I know that’s a broad statement, but it’s true. They “can” be found anywhere, but they’ll most likely only be found in deserts, or by accident by a landowner. Typically farmers are the ones who find meteorites because they dig in the dirt. Think about it, farmers must plow their fields to plant their crops, and when they do sometime they may hit a meteorite that had been covered over years before.

Weathering occurs though and meteorites tend to deteriorate over time being absorbed by the Earth. This is why it’s important for meteorite hunters and scientists to recover a meteorites as quickly as possible after a new meteorite fall because weathering starts immediately once the meteorite hits the ground. If recovery can happen fast, then the value to science is that much greater than a weathered stone.

Meteorites are found more in desert climate areas of the Earth than any other area. The deserts, both cold and hot, are perfect meteorite preservers. Antarctica is an example of a cold desert. Meteorites made of stone contain iron or are made of solid iron, and as we all know iron rusts. Corrosion and weathering take it’s toll on millions of meteorites but in a desert environment a meteorite is protected from it’s worst enemy, moisture.

Chondrules In A Stone Meteorite

Composition Of Meteorites
Meteorites are typically composed of stone type silicate minerals with an abundance of nickel iron. A small percentage of meteorites are solid iron, some are half iron and half silicates. Approximately 80% of meteorites are stone meteorites called ordinary chondrites. Only about 8% to 10% of all meteorites are made of solid iron. Stony iron meteorites are even more rare. Then you have meteorites from the Moon and Mars. These are the rarest type of all.

Most stone meteorites are called chondrites because they have what’s called chondrules. Chondrules are small spherical silicate inclusions that are found inside the stone.

Iron meteorites are of course made of iron, and they have a high concentration of nickel, more so than any terrestrial rock on Earth. Stony-Iron meteorites come in two sub-types, Pallasites and Mesosiderites. Last but not least there are achondrites. These consist of Lunar and Martian meteorites and other rare stone meteorites. They are called achondrites for their lack of chondrules.

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