ALL IMAGES COURTESY OF THE AUTHORskyandtelescope.com • FEBRUARY 2020 15
W
e are all familiar with the idea that meteorites fall
to Earth, but most of us probably think our odds
of fi nding one are rare. Yet tiny meteorites — those
less than 1 mm wide, or about the size of the periods in this
paragraph — are actually quite common. Micrometeorites
make up the bulk of the stuff that Earth collects from outer
space, and on average, one micrometeorite will land on every
square meter of our planet’s surface every year.
This cosmic dust is so common it can literally be found
under our feet. One study even turned up several dozen
micrometeorites via an exhaustive search of the rain gutters
lining city rooftops (S&T: May 2017, p. 10). However, indus-
trial contamination means that such rooftop studies are rare,
as it takes a lot of sifting to remove possible imposters.
Instead, most bits of bona fi de cosmic dust have been dis-
covered in hard-to-reach places, such as deep-sea sediments,
Antarctic ice, and the melt zone of the Greenland ice cap.
For one of these studies, researchers at the South Pole even
collected particles from the ice they had melted for drinking
water. At such remote locations, industrial contamination
is less likely. Researchers also use the size distribution and
composition of the fragments they fi nd to determine if they
truly come from space.
For enthusiasts without the means to become collec-
tors of large meteorites, micrometeorites offer an alterna-
tive — and fi nding them doesn’t necessarily require a visit
to remote locations. Although smaller meteorites are harder
to study, they’re in general more numerous. The smaller the
meteorite you’re looking for, the higher the probability youHunter
might fi nd one. And because micrometeorites are relatively
easy to fi nd, their collection and study can be just as reward-
ing as the larger variety.Collection
There are a number of ways to collect micrometeorites. I fi nd
that the magnetic ones — even though they are rare among
meteorites in general — are the easiest to fi nd and identify.
One method is to place magnets on the gutters of your
home. In New England, I like to place magnets on the down-
spouts of churches that have slate roofs and lead downspouts.
This ensures that the particles collected are not contami-
nated with asphalt roofi ng debris.
I’ve also picked up samples by dragging a strong magnet
along the silty bottom of the shores of the Finger Lakes andpCRYSTAL SURFACE This scanning electron microscope image, 80
microns to a side, shows the crystal structure on the surface of a micro-
meteorite. This meteorite is primarily made of iron, with small amounts of
other elements. Iron micrometeorites are easy to fi nd with the help of a
strong magnet.qMICKEY MICROMETEORITE The piece of cosmic dust in this false-
color image is 600 microns wide. Its appearance has a distinct quality
from that of the others because the author utilized a different imaging
mode that uses back-scattered electrons.