[meteorite-list] Researchers Change Opinion on Earth's Age

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:22:34 2004
Message-ID: <200306052136.OAA12000_at_zagami.jpl.nasa.gov>

http://www.kansas.com/mld/kansas/news/6022069.htm

Researchers Change Opinion on Earth's Age
Associated Press
June 5, 2003

WASHINGTON - The Earth became a major planetary body much earlier than
previously believed, just 10 million years after the birth of the sun, researchers say.

Experts now believe that the inner solar system planets - Mercury, Venus, Earth
and Mars - actually began forming within 10,000 years after the nuclear fires of the
sun were ignited about 4.5 billion years ago, says Stein B. Jacobsen, author of an
analysis appearing Friday in the journal Science.

Early in its life, the sun was surrounded by clouds of dust and gas. This material
slowly clumped together into larger and larger pieces. Eventually, enough was
concentrated in four bodies to form the inner solar system planets.

Within 10 million years, the Earth had reached about 64 percent of its present size
and was the dominant planetary body within 93 million miles of the sun. Mercury and
Venus orbit closer to the sun and Mars is farther out.

The final major event in the formation of the Earth, says Jacobsen, was probably the
collision with a Mars-sized planetary body. This huge smashup added many millions
of tons of material to the Earth. Some material also went into orbit of the Earth and
evolved into the moon.

This massive collision, the final major event in the Earth's formation, is thought to
have happened about 30 million years after the sun was born.

An earlier analysis of some chemical isotopes in the Earth's crust had concluded that
the planet formed about 50 million years after the sun. But Jacobsen said a
reinterpretation of the data, along with new measurements of chemicals in some
types of meteorites, supports the conclusion that Earth's basic formation came much
earlier.
Received on Thu 05 Jun 2003 05:36:39 PM PDT