I'm loving this story from The Economist:
Jon Larsen, a Norwegian musician, refused to be discouraged. He collected detritus from gutters in his hometown, Oslo, and also from rooftops in several cities that he visited to play jazz or to attend conferences. Micrometeorites contain magnetite, a naturally magnetic form of iron oxide, commonly known as lodestone.
Mr Larsen’s first step was therefore to pass his slurry, about 300kg of it, past a magnet and keep anything that stuck. He then examined the 30kg or so of debris that resulted under a microscope, to hunt for cosmic dust. Micrometeorites melt as they zip through Earth’s atmosphere at speeds of around 12km a second. The globules then cool into spherical grains, and the minerals of which these are composed take on a distinctive stripy appearance. An experienced eye, such as Mr Larsen’s, can thus pick them out from other particles, which tend to be jagged and lack these markings. Altogether, he found about 500 of these “spherules”, each around 300-400 microns in diameter (a few times the width of a human hair).Jon Larsen is a very interesting chap. Take a look at his Wikipedia profile.
Here are some micrometeorite pictures from his book: