skyandtelescope.com • FEBRUARY 2020 19
Besides analyzing a micrometeorite’s appearance, I also
identify space dust by its elemental composition. To do this,
I use a technique called electron dispersive spectroscopy. After
placing a sample in the scanning electron microscope, I
bombard it with electrons, which in turn generate X-rays.
The wavelengths of the X-ray photons produced depend on
which atoms the electrons hit, so this technique will tell me
what elements are in a specimen. A sample containing iron,
manganese, and aluminum, for example, is likely a micro-
meteorite. The micrometeorites I fi nd are generally made
of iron, with other elements such as manganese, silicon, or
nickel mixed in.
Magnetic micrometeorites represent less than 5% of all
the meteoritic debris raining down on Earth. But because
they’re also the easiest to collect and identify, I manage to
accumulate a lot of them. Dealing with huge numbers of
micrometeorites means I’m more likely to fi nd relatively
“large” specimens, with a diameter of at least 0.5 mm.
Even though you may not have access to the same
equipment, you can still fi nd micrometeorites with a fair
degree of confi dence as long as you look in the right places.
The specks may not look like much to the eye, but it’s still
rewarding to hold a little piece of the solar system on the tip
of your fi nger.¢ TED KINSMAN is a professor and high-speed photogra-
pher at Rochester Institute of Technology. He thanks Bryan
McIntyre of the University of Rochester for his help in col-
lecting X-ray spectra and for the use of his high-resolution
scanning electron microscope.tpMAGNETIC DEN-
DRITES? The circuit
board-like texture that
appears in these images
could represent magnetic
dendrites, if the fragments
are from micrometeorites.
However, this pattern can
also be found in particles
associated with indus-
trial contamination. When
scanning electron im-
ages do not tell the whole
story, as is the case here, a
spectrum can be helpful in
determining the sample’s
composition.
qSWEEPING FOR
COSMIC DUST
The author searches
along a crack in the
rocky bottom of a river-
bed (left), a surface that
acts as a natural trap for
micrometeorites. He uses
a strong magnet (right) to
aid his search.The specks may not look like
much, but it’s still rewarding to
hold a little piece of the solar
system on the tip of your fi nger.