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Finding Space rocks?

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#1 Jonzky

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Posted 06 June 2008 - 01:54 PM

Well I was just wondering how do you people find them? Are they located in certain areas.. do people run computer simulations to work out the rough location of them and then run there with metal detectors, how many Space rocks are they in the world? and finally a bit random but has anyone ever been killed by a falling space rocks? (Using the word space rock as its easier to write out all the names.)

#2 Glassthrower

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Posted 06 June 2008 - 04:46 PM

Hi Jonathan,

Welcome to the Space Rocks forum. :)

There are two main types of people who have meteorites - collectors and hunters.

Collectors, like myself, acquire our meteorites from trusted dealers, who in turn acquire them from meteorite hunters.

Meteorite hunters travel the world, chasing promising reports of recent falls. For example, an Chinese media outlet will report that a stone fell from the sky and penetrated a house in a remote rural province. The meteorite hunter hears this report, jumps on the web and starts digging for more information. Phone calls will be made. And if the report is promising enough, they jump on a plane and fly out to the site as quickly as possible. Falling meteorites are like money falling from the sky and there is a sizeable cadre of meteorite hunters who operate on a global scale. The first one to arrive on the scene has the best chance of finding the meteorite(s). In the case of a witnessed fall (where it was seen to fall, or it fell into an occupied dwelling or populated area), the meteorite is often waiting for the hunter to arrive - the locals already found it and are waiting to sell it. Or, if the fall consisted of many meteorites (hundreds or even thousands of tiny fragments if the meteor burst in mid-air), the hunter will recruit locals to help him/her scour the fields and area for meteorites - paying a bounty for specimens that are found. Depending on the landscape in question, they might be easy to see. For example, a black rock laying in the middle of a desert or a cultivated field (that was cleaned of all rocks before cultivation) is an obvious candidate. Other times metal detectors are used. A lot of "rockhound" tools and tricks come in handy here - and many meteorite hunters are also rockhounds of the conventional variety, so they can tell a meteorite from a magnetic earthly basalt by experience.

In cases where a fall took place many years ago (or even thousands of years ago), there are still meteorites waiting to be found. Most meteorites do not fall as a single large mass. In most cases they will fragment on descent and shower down a rain of fragments over an area called a "distribution ellipse" or "strewnfield" - the size and shape of the ellipse/strewnfield depends on the trajectory and velocity of the meteorite and whether or not it has fragmented into a swarm of objects. There are many documented strewnfields around the US and the world. Their locations can be plotted on Google Earth. It is still possible to visit these old strewnfields and find meteorites. Newer metal detectors which are more sensitive, and just plain old luck and determination can yield specimens from strewnfields that have been combed hundreds of times over.

Most collectors (myself included) envy the meteorite hunters. We love meteorites, but we don't get the thrill of going out into the field and discovering our own specimens. We have to rely on dealers to stock our collections. My personal collection is quite big and consists of almost every known meteorite type, but I have not found a single one in the field - I purchased them all from other dealers or directly from the meteorite hunters.

To answer your question about how many space rocks are there, MANY. I once read a figure, I don't recall it exactly, but several hundred metric tons of meteoritic material survives passage through the Earth's atmosphere and hits the surface - EACH DAY. Since 75% of the Earth's surface is covered in oceans, all of the meteorites that land in the oceans, seas or even swamps/lakes are lost. Much of the surviving material is in the form of a fine dust which is undetectable under all normal circumstances. But many sizeable meteorites fall each year, in remote areas, and they lay undiscovered until someone chances across it and recognizes it as something unusual. The Sahara Desert and Antarctica are places where many meteorites are found - because they stick out like the proverbial sore thumb once they land.

The moment a meteorite lands on Earth, it starts to terrestrialize - rot or oxidize. Meteorites were formed in the vaccuum of space and when they encounter moisture, the clock starts ticking. A celestial iron that lands in a moist area (like a jungle) will rot into a pile of oxidized shale (rust) in a matter of years.

AFAIK, nobody has been killed by a falling meteorite. I will qualify that by saying that it has not been documented to happen. There are stories, but they cannot be proven. One woman, in Alabama, was struck and injured, but she survived. Livestock including cows and llamas were killed just last year in Carancas Peru when a meteorite exploded on impact and knocked people off their feet, killing livestock, damaging homes, and left a 50-ft diameter crater. :bigshock:

Regards and clear falling skies,

MikeG


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#3 Jonzky

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Posted 06 June 2008 - 06:06 PM

Thanks for the help,

Jon

#4 Jonzky

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Posted 06 June 2008 - 06:26 PM

One more question, I saw on TV that some meteorites are made up of radioactive carbon?? Are they very dangerous do they exist a lot?

Thanks again,
Jon

#5 Glassthrower

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Posted 06 June 2008 - 11:20 PM

Hi Jon,

Meteorites contain a wide variety of minerals - depending on the type. There are 3 main groupings - stony, iron, and stony-iron. Some of the minerals are similar to or identical to minerals found on Earth. Other minerals are more exotic or exist in states not common on Earth. As far as I know, there are no dangerous meteorites, in terms of radioactivity. I am not aware of any meteorite that has been found to be radioactive enough to set off a geiger counter. Meteorites have also been floating around in space for long periods of time while exposed to cosmic radiation. But, the worst and most dangerous radioactive materials have a very short half-life. By the time the meteorite ends up on Earth (after billions of years in space), any dangerous radioactive elements would have been reduced to relatively harmless decay products.

Besides, if meteorites were dangerous, I'd be long dead. ;)

Regards and clear skies,

MikeG


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