by Corey S. Powell
how we might go
for evidence of
Our Milky Way galaxy contains tens of billions of potentially
habitable planets, but we have no idea
whether we're alone.
For now Earth is the only
world known to harbor life, and among all the living things on our
planet we assume Homo sapiens is the only species ever to have
developed advanced technology.
But maybe that's assuming too much.
In a mind-bending new paper entitled "The
Silurian Hypothesis - Would it be Possible to Detect an Industrial
Civilization in the Geological Record?"
- a reference to an ancient race of brainy reptiles featured in the
British science fiction show "Doctor Who" - scientists at
NASA's Goddard Institute for Space Studies and the
University of Rochester take a critical look at the scientific
evidence that ours is the only advanced civilization ever to have
existed on our planet.
"Do we really know we
were the first technological species on Earth?" asks Adam Frank,
a professor of physics and astronomy at Rochester and a
co-author of the paper.
"We've had an
industrial society for only about 300 years, but there's been
complex life on land for nearly 400 million years."
If humans went extinct
today, Adam Frank says, any future civilization that might
arise on Earth millions of years hence might find it hard to
recognize traces of human civilization.
By the same token, if
some earlier civilization existed on Earth millions of years ago, we
might have trouble finding evidence of it.
In search of
The discovery of physical artifacts would certainly be the most
dramatic evidence of a Silurian-style civilization on Earth, but
Frank 'doubts' we'll
ever find anything of the sort.
"Our cities cover
less than one percent of the surface," he says.
Any comparable cities
from an earlier civilization would be easy for modern-day
paleontologists to miss.
And no one should count
on finding a Jurassic iPhone; it wouldn't last millions of years,
Gorilla Glass or no.
Finding fossilized bones is a slightly better bet, but if another
advanced species walked the Earth millions of years ago - if they
walked - it would be easy to overlook their fossilized skeletons -
if they had skeletons.
Modern humans have been
around for just 100,000 years, a thin sliver of time within the vast
and spotty fossil record.
For these reasons, Frank and Gavin Schmidt, a climatologist
at Goddard and the paper's co-author, focus on the possibility of
finding chemical relics of an ancient terrestrial
Using human technology as their guide, Schmidt and Frank suggest
zeroing in on plastics and other long-lived synthetic
molecules as well as radioactive fallout (in case
ancient lizard people, waged
In our case,
technological development has been accompanied by widespread
extinctions and rapid environmental changes, so those are red flags
After reviewing several suspiciously abrupt geologic events of the
past 380 million years, the researchers conclude that none of them
clearly fit a 'technological profile.'
Frank calls for more
research, such as studying how modern industrial chemicals persist
in ocean sediments and then seeing if we can find traces of similar
chemicals in the geologic record.
He argues that a deeper understanding of the human environmental
footprint will also have practical consequences, helping us
recognize better ways to achieve a long-term balance with the planet
so we don't end up as tomorrow's forgotten species.
Then again, he's also a curious guy who's interested in exploring
more far-out ideas for finding Silurian-style signatures:
"You could try
looking on the moon," he says.
Moon is a favored target of Penn State University
astronomer Jason Wright, one of a handful of other
researchers now applying serious scientific thinking to the
possibility of pre-human technological civilizations.
like Earth are pretty good at destroying unmaintained things on
their surfaces," Wright says.
So he's been looking at
the exotic possibility that
such a civilization might have been a
If so, artifacts of their
technology, or techno-signatures, might be found elsewhere in the
Wright suggests looking for such artifacts not just on the lunar
surface, but also on asteroids or buried
Mars - places where such objects could theoretically
survive for hundreds of millions or even billions of years.
SpaceX's recent launch of a Tesla Roadster into space offers
an insight into how such a search might go.
pointed their telescopes at the car and showed that, even if you had
no idea what you were looking at, you'd still quickly pick it out as
one weird-looking asteroid.
Finding techno-signatures in space is an extreme long shot, but
Wright argues that the effort is worthwhile.
"There are lots of
other reasons to find
peculiar structures on Mars and
on the moon, and to look for
weird asteroids," he says.
Such studies might reveal
new details about the history and evolution of the solar system, for
instance, or about resources that might be useful to future
If the efforts turn up a
big black monolith somewhere, so
much the better...