Space is a fascinating place, and micrometeorites, which are little bits of meteoroid, are possibly my favourite thing in it.

Meteoroids are lumps of rock flying in space. Some meteoroids reach Earth's atmosphere and - as they trail their way through it - become 'shooting stars' or, more properly, meteors. Meteors are subject to some serious friction, which heats them enough to burn them and break them up. Sometimes there is enough of the meteor left to land on Earth. These bits of rock which crash into our fields, oceans and even buttocks are suddenly no longer 'meteors' but meteorites. Most meteors are small enough to be burned away. Of course, 'burned away' does not mean burned to nothing. Much of the meteor is reduced to dust-sized meteorites which float through the air currents of the atmosphere.

Micrometeorites, then, are microscopic meteorites. The term is used by NASA to describe the tons of meteor dust-particles which rain down on Earth every year. It is possible, and comparatively easy, to gather micrometeorites. They collect like dust in any outdoor location. One of the best places to find micrometeorites (and meteorites too) is Alaska. The undisturbed snow holds decades of build-up of micrometeorites and also contains very little pollution, dust, pollen (etc). NASA collects tonnes of snow in Alaska to be melted and sifted for meteorites and micrometeorites. It is possible for people outside of the Arctic Circle to do the same though. All you need is a magnet, a small plastic bag and a microscope.

  • Gathering. If you can't get to Alaska a good alternative is any sheltered location where this space dust will be able to build up. One example is the rainwater which washes off a slate roof after a long dry spell. A house roof will often have quantities of micrometeorites in the guttering.

  • Separating. Micrometeorites fall into two categories: metallic and rock. Metallic micrometeorites are easy to separate from normal Earth-dirt, as most dust and grime tends to be non-magnetic.

    Place a magnet inside a plastic bag and rub it through the gunk in the bottom of the collected water. Alternatively, the same covered magnet could by dredged along a river bed or the bottom of a pond. Magnetic bits will stick to the magnet in the bag, which can then be turned inside-out to keep them safe. Getting the wet metal dust out of the bag is the next step. A bit of clean water sloshed around in it will make it easy to pour them out into a container. This can be evaporated (by boiling in an oven, for example), leaving only the magnetic particles. Some of these should be micrometeorites.

  • Viewing. You now have a few dry micrometeorites sitting in the bottom of a container. A magnetized pin is a neat tool for getting some of them out of the container and under a microscope. They are, in general, round and some will be pitted.
To improve your chances of finding lots of micrometeorites, try gathering after a meteor shower. (You will find that iain noded a list of the annual showers here.)