WWW.ASTRONOMY.COM 35
he took an interest in what he
might find in the local white
chalk hills of the North Downs.
“I lived there my whole life,
and it was nice to do a project
which explored the geology where
I live,” he says. “I was doing it in
my spare time, just because I was
interested.” But the new work has
since been added to his thesis. “I
changed my title to ‘Investigating
the Sources of Micrometeorites,
Past and Present,’ ” Suttle says
with a chuckle. “Often in science
we must follow where the discov-
eries take us. You start out with a
proposal stating ‘We’re going to
do X.’ But occasionally, instead,
something you overlooked or
never knew of in the first place
turns out to be just as
interesting.”
A long road ahead
Experts such as Heck say that
Suttle and Genge’s work — and
their five new criteria for iden-
tifying fossils — could inspire
researchers to go back and take
another look at ancient microme-
teorites, especially concentrating
on spherules. This might help
them identify specimens that
had been overlooked before. “As
scientists look for these in other
locations, they will get a more
accurate idea of the numbers and
different kinds of micrometeorites
that have been fossilized,” Nittler
says. “This will give a much more
accurate picture of the past f lux
of cosmic dust.”
“It’s a step forward in enabling
others to go ahead and study
ancient micrometeorites,”
Wozniakiewicz says. And Heck
agrees. “I think it will trigger an
increased interest in the search
for fossil micrometeorites in the
sedimentary record,” he says.
“The geological record is so vast,
and deep time is so enormous,
that in order to get a good under-
standing, it’s important that more
people work on this. Right now,
it’s only a few groups. But in order
to get the puzzle together, we need
to find more puzzle pieces.”
Suttle’s collection contributes
one piece to that puzzle, notes
Nesvorny. Previous sets of
ancient micrometeorites included
specimens from around 40 mil-
lion years ago, as well as those
from 170 million years ago and
older. However, “There’s a huge
gap between 40 million and
170 million,” Nesvorny says.
“This is the first sample from
that interval.”
After finishing his Ph.D.,
Suttle completed a postdoctoral
position at the University of Pisa,
where he studied a new collection
of “giant” micrometeorites recov-
ered from cracks in the tops of
Antarctic mountains. Most of
these modern micrometeorites
are millimeter-sized fragments
of water-rich asteroids that fell to
Earth in the past 1 million to
2 million years. By analyzing
their chemistries, textures, and
compositions, researchers can
learn about the early lives of
planetesimals, which were objectsroughly 62 miles (100 kilometers)
wide that were the precursors
to the planets. This is because
the interaction between liquid
water and silicate rock on these
bodies represents a snapshot of
the planet-forming era.
Now, one of Suttle’s next goals
is about semantics.
For years, all space dust par-
ticles were commonly referred to
as fossil micrometeorites, no mat-
ter whether they were truly fossil-
ized or remained unaltered. “I’m
forced to call those other collec-
tions fossilized, because that’s the
word people use. I’d like to
change it,” Suttle says. Calling
nonfossilized micrometeorites
“ancient” would draw a clear dis-
tinction, he adds. “This is some-
thing I’ve been on a bit of a
personal campaign about.”Award-winning writer Ilima Loomis
is the author of Eclipse Chaser:
Science in the Moon’s Shadow
(Houghton Mifflin Harcourt, 2019).Cosmic dust particles
may be small, but they
move so quickly (tens of
thousands of miles per
hour) that they can do
some real damage to
anything they strike
that’s beyond Earth’s
protective atmosphere.
For example, this image
from 2006 shows a tiny
hole created when a
micrometeorite struck a
panel on NASA’s Solar
Maximum Mission. NASA