NASA researchers: Comet shower triggered life on Earth
April 17, 1997
Web posted at: 7:00 p.m. EDT
From Correspondent Don Knapp
SAN FRANCISCO (CNN) -- It's one of the amazing, puzzling
questions about the origin of life on Earth: What was the
trigger that led to the formation of those primitive life
forms that crawled out of the primordial soup many eons ago?
Two NASA researchers now say we may have some distant comet
cousins of Hale-Bopp to thank for life itself.
Comets crashing into the Earth brought water, nitrogen and
carbon dioxide that make up our atmosphere. But researchers
Chris McKay and Bill Borucki have demonstrated that the
crashing itself may have been a key event in the origin of
McKay and Borucki created a vial of gas simulating the best
guess of scientists as to the composition of the early
atmosphere. They then mimicked a collision of a comet and
Earth by aiming a laser blast at the primitive mix.
What they found was that the powerful shock waves from this
"micro" blast created temperature and pressure changes that
altered the molecular composition of the pseudo-atmosphere.
"Those new molecules, when mixed in with water, form amino
acids. They're the start, the first step toward life,"
Comet strikes common in Earth's formative years
Today, comet sightings such as Hale-Bopp and Halley are rare.
That's because, through the ages, the planets themselves
attracted most of the comets in the universe, leaving but a
few to roam loose through the skies.
But 3.9 billion years ago, in the late formative period of
the Earth, scientists believe comets were decidedly more
common. Crater evidence shows they were then bombarding the
moon -- an indication that they were also probably striking
"Just think what it must have been like 3.9 billion years ago
when the sky literally would have millions of such [comet]
images, and thousands of them would be slamming into the
surface, creating quite a havoc here on Earth -- but also
creating the stuff that might have led to life," McKay says.
Many ancient civilizations regarded comet sightings to be
significant events. It may turn out that comets were perhaps
more significant than even the ancients thought.
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