They're not easy to find, but then again... not that many people are looking.
As astronomers, we're always delighted to see a meteorite streak across the night-sky while we're setting up our scopes or scanning the constellations for our next setup. At other times, we're carefully observing an area of the sky in anticipation of a meteor shower. On some rare occasions we are left wondering in amazement as a meteorite streaks down and over the horizon. Where did it land? We wonder. And will someone find it?
The answer is that thousands of meteorites land on the Earth's surface each year. In fact, according to The Monthly Notices of the Royal Astronomical Society, 18,000 to 84,000 meteorites strike the Earth each year, although other estimates put the total annual number as low as 500. To date, it's reported that 40,000 meteorites have been found. That sounds like a small number, but once again there aren't that many people who take the time to look for them.
Image credit: NASA.gov
You Can Do It
Most meteorites that we might find are smaller pieces of larger meteoroids that have broken up as they travel through Earth's atmosphere. The fact is they're out there and not that many people are looking for them so you have a good chance of discovering one if you know how and where to look, and what to look for.
One Indispensable Tool - The Neodymium Magnet
The one, simple tool every meteorite hunter uses is something called a "Neodymium" magnet attached to the end of a stick or cane. Neodymium magnets attract rare earth metals in addition to the iron that is common in many meteorites. You must be careful though as these magnets are very strong. So keep them out of reach of children and don’t let two attract to each other as they could shatter.
Types of Meteorites
For the record, meteorites typically occur in 3 types.
1. The iron meteorite - consisting mostly of iron. These are the meteorites attracted to the Neodymium magnet, but only 5% of meteorites that reach the earth are of this type.
2. The stony meteorite - or "chondrite" is made up of the rocky material from its source. They often have circular inclusions or "chondrules" from the gases that escaped in the heat of entry and can be any size from fist sized to the smallest pebble. Stony meteorites could be from a planet or asteroid, or pieces flung into space as a result of a planet/asteroid collision. 80 to 95% of the meteorites that fall to Earth are rocky meteorites.
3. The stony/iron meteorite - these usually consist of a 50/50 mix of iron and silicates. They are also very heavy for their size. Only 1 to 5% of falls have this stony/iron combination.
What's important to remember is that a rock with a stone-like appearance that is attracted to a magnet increases the odds that you may have found a meteorite.
Images by: NASA.gov
What Are the Odds of Finding One Yourself?
While it may seem you're more likely to find a rocky meteorite given the 95% fall-rate, 80% of the finds are metallic, while only 20% are pure rock. This is due to the ease of finding an iron meteorite with a Neodymium magnet, the fact that metallic meteorites don't erode as quickly as rocky meteorites, and the striking appearance of most iron/metallic meteorites.
In fact, many meteorite hunters don't know a rocky meteorite when they find them, or mistake an unusual rock of Earth origin for a meteorite. The common term for this mis-identification is a "meteorwrong."
Tool Number 2 - A Field Guide to Meteorite Identification
The second tool you might want to consider is either a book that shows you the appearance and types of meteorites, or a club where experienced meteorite hunters can give you some tips and advice. Most look for any magnetic properties, a black, fused outer surface that would indicate some level of exposure to high heat upon entry into the atmosphere, and in some instances a weight that seems greater than you would expect for a rock that size. Be mindful of the fact that after some meteorites have weathered with time the colour can vary from black to either brown, yellow, orange, or a reddish appearance. There are other tests that include sawing a sample in half with a diamond saw to look for a unique pattern in the interior, but that will spoil the sample.
Rust on the exterior of a sample can also indicate a meteorite find, but be careful. Hematite and Magnetite also rust and are attracted to magnets. The easiest way to know is do a streak test. Hematite and Magnetite will both leave a coloured streak on rough piece of porcelain or ceramic or on a geologist's streak stone. Hematite will leave a rust coloured streak and Magnetite a dark, gray streak. Meteorites leave no streak unless you press extremely hard and it will usually be a very light, grayish colour.
Where to Look
Unfortunately, knowing what they look like and simply assembling tools for a meteorite hunt won't guarantee you'll find them. You need to know where to look.
Some of the best meteorite hunting grounds are dry lake-beds; any large, barren expanses where there are few terrestrial rocks; deserts, icy regions (the most meteorites have been found in Antarctica), or something called "strewn-fields."
Strewn-fields are zones where meteorites from a single space rock were dispersed as it broke into pieces as it exploded in Earth's atmosphere during entry. Recently, many small pieces of the meteorite that exploded over Chelyabinsk, Russia are being found by people living in the area even when they weren't looking for them. The strewn-field is enormous.
To locate potential strewn-fields in your area you can check with the local conservation office, or search the internet. Even if you can't find a strewn field and deserts aren't particularly common in your area, any walk across open ground with your Neodymium magnet stick might surprise you.
If and when you do find success you might get the bug to continue your meteorite hunts. In that case you might want to add some tools for your expeditions.
Tool Number 3 - GPS and Notebook
A handheld GPS and notebook is a good addition. If you find a meteorite you can identify the position. Who knows, maybe you've found a new strewn-field no one knows about. It also helps to remind you where you've hunted in the past so you don't cover the same ground again.
Tool Number 4 - The Metal Detector
You might also want to consider a metal detector. This is particularly useful in known strewn-fields and allows you to investigate more than what meets the eye on the surface. You should try to buy a metal detector with "gold detecting" capability. These are more sensitive although you might dig up a few tin cans in the process.
Tool Number 5 - Digital Camera
A digital camera also comes in handy to take a photo of the place, terrain and any specimens you've found. Many smartphones combine GPS, note-taking and digital cameras and they sure come in handy if there's a few of you hunting over a large area. This lets the person who's found the first meteorite to alert the others to a potential strewn-field. You can also download your field guide to the smartphone and pretty much have an all in one tool.
Hopefully, you'll find success after a few hunts. The ability to hold in your hand a piece of the universe that has potentially traveled millions of miles from places we can only observe, study and wonder about. It's a thrilling feeling for an astronomer and hopefully for you. Under UK law, a small sample of the meteorite - 20 per cent of the total mass, or 20gms, whichever is the smaller - must be donated to an institution. The rest is owned by the finder, and/or landowner. Be sure to check your country’s own laws on collecting meteorites.
Here is an article on the fascinating story of the Agoudal Meteorite.
References for Further Reading:
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