Open Magazine – August 07, 2018

(sharon) #1

6 august 2018 http://www.openthemagazine.com 33


longing to the Paleoproterozoic era. This is
the period spanning 2.5 to 1.6 billion years
ago, when continents first began to stabilise
and, according to some, the planet had 20-
hour days and 450 days a year, thanks to its
rotational rate. Knowing this could be his
best bet, he had picked the Champua area.
Champua is a remote and rural loca-
tion in odisha, bordering Jharkhand,
about four-five hours by road from Jam-
shedpur. It is replete with deep forests,
hills, valleys, and large and small rocks
that appear everywhere. according to
Mazumdar, over the years, several of these
rocks taken back to laboratories have been
throwing up very early dates, indicating
that they could’ve been part of a very an-
cient crust.
“It’s really a nice little place for geolo-
gists,” he says. “It’s not been the point of fo-
cus [for geologists globally] like Jack Hills
[in western australia, an area which has
resulted in several important geological
studies] or places in Canada. But the clues
have all been there [in Champua], and we
geologists from India have been finding
some interesting things here and there.”
For the next year, over several trips,
each lasting a few days, Mazumdar and
Chaudhuri covered the area on foot, scan-
ning it for any rock that might look old.
To an untrained eye, these rocks might
appear unimpressive, Chaudhuri says.
“There’s nothing special about them at all.
But us geologists, we can tell,” she says. “so
we just walked and browsed.”
Every trip resulted in bags of rock
pieces, 10-20 kg each, which they either
sent through buses or carried with them
in a cab, back to their labs in Kolkata. once
in their labs, Mazumdar and Chaudhuri
managed to retrieve zircon crystals from
these samples. Zircons are tiny crystalline
minerals, barely spanning the width of a
human hair but near indestructible. They
form in magmas and incorporate other
minerals within their crystal structures.
and even though rocks perish over time,
zircon crystals can survive for billions of
years, offering us a rare glimpse into the
earliest pages of Earth’s history.
Mazumdar and Chaudhuri were quite
certain that they had found some inter-
esting samples. But the technology and


machinery to deal with zircon minerals,
to date them or analyse their isotopic
and elemental nature, is expensive and
unavailable in India. For the next eight
years, Mazumdar says, he approached
foreign labs in australia, Japan, Canada,
the us and germany to have a look at
their samples, but failed to interest them.
“The whole process is quite expensive.
Most of these labs are already commit-
ted to their projects. and they are usually
not too interested to check samples from
areas that haven’t previously produced
anything interesting,” he says.
Mazumdar eventually managed to
convince a lab in China—the Beijing
sHRIMP (sensitive High Resolution Ion
Microprobe) Centre under yusheng Wan
at the Chinese academy of geological sci-
ences—that was willing to analyse the
samples on a collaborative basis. But yush-
eng had a condition. “He was very clear.
He was willing to do it, but said he would
examine only four samples,” Mazumdar
says. He jumped at the opportunity.
Close to seven years since he first dis-
covered the samples, last year Mazum-

dar got a call from Beijing. It was yusheng
Wan. “He said, ‘you were right, they are
very, very old,’” Mazumdar says.
Their findings were recently pub-
lished in Scientific Reports, a journal from
the publishers of Nature. Three of the sam-
ples turned out to be 3.4 billion, 3.7 billion
and 4.03 billion years old. and the fourth
sample, found to be 4.24 billion years old,
was the second oldest material ever found
on this planet.
Earth came into existence around 4.5
billion years ago, along with the rest of
the solar system, from the wreckage of
an exploded star. But this early Earth was
no Eden. For the next half-billion years,
as the story goes, Earth was covered with

gurgling oceans of magma and continu-
ously pummelled by meteorites and cos-
mic detritus. one such strike, possibly
with another planet, led to a chunk of
our planet splintering off to become the
moon. For those years, Earth was hot and
inhospitable, with no liquid water or any
possibility of life. This period is considered
to be such a hellish one that geologically
the era is named after the greek word for
the underworld—Hadean.
Life could emerge—as simple single-
celled prokaryotic cells, as the theory
goes—no earlier than 3.8 billion years ago,
once the violent bombardment of meteor-
ites had ceased, the oceans of magma had
receded, and water finally appeared.
These are at best educated guesses. The
early years of Earth’s history are still a mys-
tery. The everyday churn of our planet for
4.5 billion years—the meteorite impacts
and volcanic eruptions of our ancient
past, the movement of our tectonic plates
and the erosion of our rocks—has meant
that nothing from this early period has
survived. There are no primeval rocks or
relics that could reveal how things exactly

were. Except for zircons, that is.
“Zircons are like these tiny windows—
the only window, really—to what was go-
ing on on our planet 4 billion years ago,”
Chaudhuri says.
Zircon crystals often incorporate other
minerals like silicon, oxygen and zirco-
nium into their structures. They are used
in imitation diamonds and jewellery. But
some of them—like the ones discovered
by Mazumdar and Chaudhuri—can be in-
credibly old and they contain within their
tiny structures the stories of our planet’s
earliest time.
While their original host rocks have
long disintegrated, these tiny indestruc-
tible structures have remained, moved

the early years of earth’s history are still a
mystery. there are no primeval rocks or relics
that could reveal how things exactly were.
except for zircon crystals, that is
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