Hunt for meteorites in your own yard

You can collect micrometeorites anywhere.

Micrometeorite
Micrometeorite
An isolated micrometeorite about 0.5 mm in diameter.Henri Galimberti on Flickr via CC 2.0

When you picture a meteorite, you probably imagine a massive hunk of space rock hurtling its way through Earth's atmosphere. The objects that survive this trip sell for tens of thousands of dollars at auctions, become parts of museum displays, and make national news. But you—yes, you—can find your very own meteorites, and you don't need to be a millionaire to do it. You just need to think small. Micro, to be exact.

Like meteorites, micrometeorites are space rocks that fall to Earth—but as their name suggests, they are also extremely tiny, less than a tenth of an inch in width. And they're way more numerous than their big cousins: Approximately 3,000 tons—that's roughly the weight of 47 sperm whales—of micrometeorites smash into the ground each year, compared to a piddling 55 tons of meteorites. Which means some of these objects could be sitting in your backyard right now.

There's just one problem: How do you expect to dig up wee rocks that range from a fraction of a millimeter to 2mm in diameter (switching to metric units for specificity's sake)? Luckily, many micrometeorites are magnetic, which means you can collect them by simply dragging a strong magnet over the ground. (Of course, it's a little more nuanced then that—keep reading for more information.)

Norwegian researcher Jon Larsen has hunted micrometeorites all over the world, and he wants to recruit amateurs into the space-rock-collecting club. While his full instructions for finding micrometeorites are detailed, they also include directives, such as weighing each sample and keeping careful notes, that will appeal more to serious researchers than to casual collectors. Read on for a stripped-down version of his rubric. Happy hunting!

Tools and materials

  • Three clear plastic sandwich bags
  • Permanent marker (optional)
  • Neodymium magnet, ideally with a hook to use as a handle
  • Twist ties or rubber bands
  • String (optional)
  • Gloves (optional)
  • Coarse sieve (opening around 1.5 mm wide, Number 12 or 14 mesh)
  • Fine sieve (opening around 0.4 mm wide, Number 40 or 45 mesh)
  • Plate or shallow dish, water, and dish soap (optional)
  • Glass slide
  • Microscope
  • Toothpick

Instructions

  1. Reserve one of the sandwich bags, optionally marking it with the date and the location of your collection foray. This will act as a receptacle for your micrometeorite samples.
  2. Wrap the neodymium magnet in the two remaining sandwich bags so that two layers of clear plastic sit flat over the magnet. One layer will prevent the micrometeorites from getting permanently stuck to the strong surface, and the other will act as a backup in case the first one tears.
  3. Secure the bags by fastening their openings around the hook with a twist tie or rubber band. Optionally, tie a string around the magnet so you can suspend it as you run it over the ground, rather than crouching down to drag it.
  4. Place the plastic-covered magnet on a rooftop, sidewalk, or your own backyard, and pull it around all over the area. You'll probably have the most luck in an area that concentrates downpours, like in gutters or the spots where they empty out.
  5. The neodymium should attract any magnetic particles, eventually covering the plastic in a layer of grimy-looking…stuff. You may want to wear gloves when handling it.
  6. Holding the magnet over the first, labeled sandwich bag, pull away the plastic layers. Once they're free of the magnet, any micrometeorites on the plastic will fall into the clean sandwich bag.
  7. Repeat this process until the sample bag contains a decent scoop of grime. Then wash your hands thoroughly and take your finds home for the next steps.
  8. Run the contents of the bag through a coarse-meshed sieve and then a fine-meshed one to sort the sample into three different piles.
  9. Material that didn't fit through either sieve is wider than 1.5 mm, and probably doesn't contain micrometeorites. Material that fit through both sieves is less wide than 0.4 mm and will be more difficult to handle. Instead, we'll concentrate on the Goldilocks material that fit through the coarse but not the fine sieve.
  10. If your Goldilocks sample just looks like dirt, place it on a plate or a shallow dish and wash it with warm water and a little bit of dish soap.
  11. Scoop some of the clean material onto a glass slide and place it under the microscope so you can see it up close. Not every magnetic particle you pick up will be a micrometeorite, so concentrate on looking for tiny metallic spheres. While you search, you can wield a toothpick to move the material around, spread it out, or isolate a particularly promising-looking piece.
  12. When you find these spheres, zoom in to examine the details on their surfaces. Then compare your findings to the objects on Larsen's Project Stardust page. You may turn up a decent number of human-made magnetic particles before you find the micrometeorites you seek, so remember to be patient.