S
28 ASTRONOMY • AUGUST 2020
Like dinosaur bones, tiny
micrometeorites reveal much about
the ancient past. BY ILIMA LOOMIS
EXCAVATING
COSMIC FOSSILS
omething was wrong with
Martin Suttle’s micrometeorites.
The Ph.D. student at Imperial
College London had collected 76
tiny grains of space dust that had
fallen to Earth near the white
chalk hills of the North Downs,
close to his home in Kent,
England. When Suttle used a
microscope to study the sand-
sized particles — found in a layerof 87-million-year-old rock —
he recognized the characteristic
shape of small round spherules,
like metal droplets. But when he
cut them open and looked inside,
he was surprised by what he saw.
Where Suttle expected to find
nickel, a common metal in mete-
orites, he instead found manga-
nese, an element more associated
with the geological processes ofEarth’s deep-sea f loor. He
scanned more particles with
the same results. Suttle left the
microscope disheartened. The
samples looked like space dust,
but the geochemistry was wrong.
“I was kind of disappointed,”
says Suttle, who is now a plan-
etary scientist and geologist at
the Natural History Museum in
London. “I thought, ‘Oh, these