By Ronald Kotulak
Tribune Staff Writer
January 11, 2001

Taking to heart the poet Blake's advice "to see a world in a grain of sand,"
an international team of scientists say that by examining the oldest grain of
sand ever found, they have been able to see the world as it looked shortly
after it was born.

Using powerful new probes to read the information locked inside the 4.4
billion-year-old crystal, so old that it was created a mere 100 million to 200
million years after the Earth was formed, the researchers are rewriting the
early geological history of the planet.

Their stunning discoveries--that the grain contains evidence of liquid water
and continental crust--are shaking up long-accepted notions of the fledgling
world.

Geology textbooks say the infant Earth was a lot different from what it is
today. For hundreds of millions of years, according to the prevailing theory,
Earth was a hellish place, cloaked in boiling clouds, covered by a molten
surface and much too hot for water vapor to condense into seas.

But the new findings, reported Wednesday in the British scientific journal
Nature, indicate that the Earth was far more hospitable. It quickly became
paradiselike, taking on the shape we see today with vast oceans, magnificent
continents and relatively mild temperatures.

"To find evidence of water in a 4.4 billion-year-old grain of sand is just
fantastic," said University of Wisconsin geologist John Valley, who heads the
international team.

"It tells us that the early Earth was a lot more like what we are familiar
with," he said. "It says that the Earth did not go through 600 million years
of looking like Venus. You wouldn't have just gotten off a spaceship and
started planting daisies here, but it wasn't like being in the center of the
Earth in terms of fire and brimstone."

Venus, Earth's sister planet, is perpetually shrouded in thick sulfurous
clouds that make its surface hot enough to melt lead.

"Their findings are really exciting," said Lawford Anderson, chief of earth
sciences at the University of Southern California. "They are filling in the
lost chapter. We know that the Earth is 4.5 to 4.6 billion years old, but up
till now the oldest rock that has been found was only 4 billion years old. To
have the first 600 million-year history of our planet not recognized in the
geologic record was very frustrating."

The findings also mean that the conditions for the origin of life occurred
much earlier than previously thought. The oldest known fossils of living
organisms are 3.5 billion years old.

"It could be that primitive, one-celled forms evolved as early as 4.4 billion
years ago," Valley said. "Life like that could have been repeatedly
extinguished by giant meteor impacts like the one that is believed to have
wiped out the dinosaurs.

"Life may have evolved many times. We are the descendants merely of the last
and successful evolution of life."

Allan Treiman, senior staff scientist at the Lunar and Planetary Institute in
Houston, who has been following the research, agrees.

"It's a really big discovery," he said. "The most important part of it is the
oceans, the evidence of liquid water very early on. We all sort of assumed
that the young Earth was very hot.

"But to find evidence of liquid water is a real big deal. It also feeds into
the notions of the origin of life. If there are oceans available at 4.4
billion years, it gives life a little bit longer to get started. It gives life
a little more time to show up than had been thought before."

The sun is believed to have condensed from a gigantic swirling gas and dust cl
oud about 5 billion years ago. The Earth and other planets in our solar system
are thought to have accreted from the leftover material circling the sun about
a half billion years later.

The findings also throw into question the formation of the moon, making it
more likely it was captured by the Earth's gravity rather than being torn out
of the Earth by the impact of a Mars-size planet.

The moon is believed to be 4.45 billion years old. If it were formed from a
gigantic impact, the Earth would have been heated to the melting point and
would not have cooled down fast enough to allow the thick clouds of steam to
condense into oceans by 4.4 billion years.

Extracting so much information from a single grain of sand, which is only as
big as the width of two human hairs, was recently made possible by the
development of new technology.

As small as the sample is, new tools enable scientists to read the grain like
a history book. Lasers and ion beams knock off clumps of atoms from inside and
outside of the crystal, and then a mass spectrometer is used to determine
their age, chemical content and the conditions under which they were
formed.

"The reason we focus on this single grain so much is that it's a rare remnant
of this early continent," said Colgate University geologist William Peck, a
member of the international team. "We are really trying to get as much out of
this lonely little crystal as we can."

Other team members who examined the grain include Simon Wilde of Curtin
University in Australia, who found the rock containing the ancient crystal in
the Jack Hills of Western Australia, and Colin Graham, who studied the grain
at the University of Edinburgh with Peck to find evidence of liquid water. The
crystal is now back at the University of Wisconsin.

"It used to be we had to dissolve 10 to 15 grains to get an average age,"
Anderson said. "Now we can analyze a single grain like reading tree rings. The
neat thing is they went inside the crystal and found that the oldest portion
was 4.4 billion years with a 99 percent degree of accuracy. It is the oldest
age on Earth."

Finding anything almost as old as the Earth itself is extremely lucky. The
continents are continually being recycled from erosion and the constant
destruction and formation of the crust and sea floor by the Earth's hot
interior. As rocks melt, their age is reset to zero. That's why there are no
rocks in the ocean floor older than 200 million years.

The crystal under study is zircon. Zircon is a common sky-blue gemstone formed
in the hot lava of volcanoes by the combination of the elements zirconium,
silicon and oxygen. Typically they are part of the makeup of granite rock that
forms when lava cools.

But among all rocks, zircon is special. It is nearly indestructible, it keeps
track of the time from its birth and it remembers the conditions under which
it was born.

Geologists are making great strides in identifying older and older rocks.
Three years ago a zircon-containing rock dating back 4 billion years was found
in Canada's Northwest Territories.

While granite may seem to last forever, over billions of years it erodes and
its zircon crystals fall free, becoming grains of sand. The crystal found by
Wilde most likely was carried down a stream and eventually deposited on an
ancient beach.

Over time the beach sand with its zircon crystal hardened into sandstone, the
rock that Wilde found and which he determined was 3.75 billion years old.
Researchers from the University of California at Los Angeles have since found
zircon crystals as old as 4.3 billion years.

"You can learn a lot from a grain of sand," Houston's Treiman said. "What it
is telling us is that the early Earth seems more like a modern place with
oceans and continents."

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