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Ask Slashdot: What Gadgets Would You Use For Hunting Meteorites? 130

Posted by Soulskill
from the can't-beat-a-trusty-tricorder dept.
DrPeper writes "I may have an opportunity to assist a pair of renowned meteorite hunters (yes, the ones on the Science Channel). Being the MacGyver-type everywhere I've worked and a consummate geek, I thought I would pose a question to the Slashdot community. If you were to go meteorite hunting, what gadgets would you use? I've already thought of using a UAV with a radio gradiometer, or attaching a coil to a quadrocopter, blimp, or terrestrial robot. (The point of which would be to have it automatically produce a gradient map of the density of ferrous metals in a given area.) Any other crazy ideas out there?"
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Ask Slashdot: What Gadgets Would You Use For Hunting Meteorites?

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  • by rgbatduke (1231380) <rgb@phy.dukDEGASe.edu minus painter> on Friday March 25, 2011 @07:58PM (#35618282) Homepage
    The easiest possible way to collect meteorites is to place a large, flat pan out on your back deck (or a large funnel with a fine screen like those they sell at breweries). Leave it out to collect rainwater. After a few heavy rains, you will notice that there is a small amount of fine grit in the filter or in the bottom of the pan. Carefully drain the water out of it and let it dry the rest of the way. Dump it out on a sheet of white paper, and go over the grit with a powerful magnet (like the ones that come inside old hard disk drives) wrapped in a plastic bag.

    Usually about 1/3 to 1/2 of the grit will be attracted to the magnet. It is made up of fragments of small nickel-iron meteorites of the sort that constantly rain in upon the Earth every day and that are one of many things that nucleate rainwater drops. A lot of the remaining grit is probably meteor dust as well, but stony meteor dust, and since some fraction of it is just plain old dust blown up from the ground, it is difficult to differentiate. But chunks of iron falling from the sky are probably meteor material.

    This is actually a fairly entertaining thing to do. You can look at the chunks you collect at maybe 10-30 power under a microscope, and see that they often do look melted and fused like their larger cousins. If you run a trap for a while and pull out the ferrous micrometeorites regularly, you can actually build up a small vial full of the stuff. My kids each did this as elementary science fair projects when they reached the right age, and it was always one of the most popular of displays.

    Finding larger meteorites isn't terribly difficult either as they constantly fall as well, but identifying them is more difficult. A rock, after all, looks a lot like a rock. Stony meteorites may not look like the right kind of rock for some location, but a non-expert isn't going to see the difference easily. Iron meteorites again are the easiest ones to identify if not find -- unless you live near an iron mine, an isolated chunk of iron-rich rock has a decent chance of being a meteorite. For these, good metal detectors can help.

    Some places make it easier to find meteorites than others. If you wander around in the middle of a big, arid, flat, desert, meteor craters sometimes stand out, unweathered, or stray rocks out on the surface turn out to be meteorites. Plowed fields and so on again let you look over a large surface area in a relatively short time, but even so it is a crap shoot. The only decent sized meteorite I've found I found without a metal detector -- it was a heavy, iron-rich rock out of place in the middle of a field. But anybody can find the micro-kind, right in their own back yard!

    As for equipment -- the same hard-disk drive magnet that you use to pull out the micrometeorites, securely attached to the end of your walking stick, is a great way to find them. If you're walking through a field (again in some part of the country not known for having native iron deposits) and your walking stick happens to pick up a chunk of possibly fused-looking rock, well, there you are!

    rgb
  • Ok, a serious answer (Score:5, Interesting)

    by jd (1658) <imipak&yahoo,com> on Friday March 25, 2011 @08:15PM (#35618390) Homepage Journal

    First off, you want access to Google Earth and survey the terrain for any vegetation bands that indicate a subsurface anomaly. If the crater is too small for Google Earth's resolution, then use a weather balloon and a camera. If there's no vegetation, or it's too thin to show anomalies up, try a camera that can see into the infrared and take the picture at dusk. The difference in subsurface features will produce a difference in heat output.

    That tells you where a crater is and which direction it is facing, therefore it will tell you which direction the ellipse for the strewn field will need to point.

    A magnetometer is probably a better bet than GPR (which they've tried in the past without much luck). Combine it with a resistivity meter [archaeologywordsmith.com]. Meteorites all contain iron AND nickel (and other trace elements). By knowing the resistivity, you can distinguish a meteorite from any other type of iron. Depending on the age of the impact and climate, you may also be able to detect debris from how it has altered soil chemistry via this method.

    For the magnetometer, you want a proton magnetometer [gerf.org]/gradiometer, as that's the most sensitive. The link is to a site on how to build one.

    They have the world's largest metal detector, but you should be able to make one larger. Furthermore, it's a loop so it is detecting metal above the detector as well as in the ground. What you ACTUALLY want is for the detector to only look at the ground. A suitable reflector should not only achieve this but double the sensitivity at the same time.

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