‘Life on Earth likely
started 4.1 bn years ago’
University of California Los Angeles
(UCLA), United States (US), geochemists have found evidence that life likely existed on
Earth at least 4.1 billion years ago — 300 million years earlier
than previous research
suggested. The
discovery indicates
that life may have
begun shortly after the
planet formed 4.54
billion years ago.
The research was
published Tuesday in
the online early
edition of the journal
Proceedings of the
National Academy of
Sciences.
“Twenty years ago, this
would have been
heretical; finding
evidence of life 3.8
billion years ago was
shocking,” said Mark
Harrison, co-author of
the research and a
professor of
geochemistry at UCLA.
“Life on Earth may
have started almost
instantaneously,”
added Harrison, a
member of the
National Academy of
Sciences. “With the
right ingredients, life
seems to form very
quickly.”
The new research
suggests that life
existed prior to the
massive bombardment
of the inner solar
system that formed the
moon’s large craters
3.9 billion years ago.
“If all life on Earth
died during this
bombardment, which
some scientists have
argued, then life must
have restarted
quickly,” said Patrick
Boehnke, a co-author
of the research and a
graduate student in
Harrison’s laboratory.
Scientists had long
believed the Earth was
dry and desolate
during that time
period. Harrison’s
research — including a
2008 study in Nature
he co-authored with
Craig Manning, a
professor of geology
and geochemistry at
UCLA, and former
UCLA graduate student
Michelle Hopkins — is
proving otherwise.
“The early Earth
certainly wasn’t a
hellish, dry, boiling
planet; we see
absolutely no evidence
for that,” Harrison
said. “The planet was
probably much more
like it is today than
previously thought.”
The researchers, led by
Elizabeth Bell — a
postdoctoral scholar in
Harrison’s laboratory
— studied more than
10,000 zircons
originally formed from
molten rocks, or
magmas, from Western
Australia. Zircons are
heavy, durable
minerals related to the
synthetic cubic
zirconium used for
imitation diamonds.
They capture and
preserve their
immediate
environment, meaning
they can serve as time
capsules.
The scientists
identified 656 zircons
containing dark specks
that could be revealing
and closely analyzed
79 of them with Raman
spectroscopy, a
technique that shows
the molecular and
chemical structure of
ancient
microorganisms in
three dimensions.
Bell and Boehnke, who
have pioneered
chemical and
mineralogical tests to
determine the
condition of ancient
zircons, were
searching for carbon,
the key component for
life.
One of the 79 zircons
contained graphite —
pure carbon — in two
locations.
“The first time that the
graphite ever got
exposed in the last 4.1
billion years is when
Beth Ann and Patrick
made the
measurements this
year,” Harrison said.
How confident are
they that their zircon
represents 4.1 billion-
year-old graphite?…”
