Earth could have had oceans very early in its history According to CNN news broadcaster Elizabeth Landau, the oldest slice of Earth was found - From a sheep ranch in Western Australia
Scientists say they have
dated an ancient crystal called a zircon to about 4.4 billion years,
making it the earliest confirmed piece of the planet's crust. The
findings -- the first to describe the zircon -- were published in the
journal Nature Geoscience on Sunday.
"This is the oldest and
the best dated of all the crystals that have been reported," said John
Valley, lead study author and professor in the Department of Geoscience
at the University of Wisconsin-Madison.
This crystal is a
translucent red, Valley said, but glows blue when bombarded with
electrons. At 400 micrometers long, its biggest dimension is just a tad
larger than a house dust mite, or about four human hairs.
The crystal was found in an arid region north of Perth, Australia, in a low range of hills called the Jack Hills, in 2001.
Scientists say the
crystal's chemistry -- specifically, the ratio of oxygen isotopes within
it -- suggests that the temperatures on Earth 4.4 billion years ago
would have supported liquid water, and therefore perhaps life. Two
isotopes of an element are considered different if they contain
different numbers of neutrons.
What we've learned is that the Earth cooled much more quickly that
people had thought," Valley said. "The surface formed a crust much more
quickly than people thought."Now let me tell you a brief history of Earth:
Our planet is thought to
be about 4.54 billion years old, but the entire fossil record only goes
back 600 million years. That doesn't necessarily mean that no life
existed before that time, but no direct evidence has been found yet.
The first rocks that have been found deposited by water are about 3.8 billion years old, Valley said.
But very little is known
about the first 600 million years or so of the planet's history, known
as the "Hadean Eon" because it was thought to be "hell-like," Valley
said.
The leading theory is
that Earth was bombarded by meteors in its early history. It took a big
hit from an object the size of Mars about 4.5 billion years ago, leading
to the formation of the moon. These impacts vaporized the Earth's crust
and formed a super-hot magma ocean.
Evidence including this
zircon suggests that within the first 100 million to 200 million years
of its existence, our planet cooled enough to make crust. Steam from the
atmosphere condensed to make oceans.
"Once you know that
there were oceans, it's very reasonable that there would have been life
that early" -- even when it was only 200 million years old, Valley said.
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