SETI bioastro: Impacts that changed life on Earth

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From: LARRY KLAES (ljk4@msn.com)
Date: Fri Feb 22 2002 - 08:52:36 PST


SCIENTISTS SIMULATE COMET STRIKES: FINDINGS MIGHT SHED LIGHT ON ORIGINS
OF EARLY EARTH LIFE

>From Orlando Sentinel, 17 February 2002

http://www.orlandosentinel.com/

By Andrea Widener, Knight Ridder Newspapers

WALNUT CREEK, Calif. -- The large bullet rips down the gun's long barrel at
the mind-bending speed of 4,500 miles per hour.

In fractions of a second, it strikes its target with a dull thump.

With this target, a shiny silver capsule filled with a teardrop of water,
scientists are simulating the scorching impact of a comet striking the
Earth.

These intense temperatures and pressures, while lacking the violence of real
comet strikes, are giving scientists insights far beyond what has been
available up to now.

Experiments by Jennifer Blank at Lawrence Livermore in Livermore, Calif.,
and a small group of others are shedding light on one of science's most
fundamental questions: How did life begin?

The implications of comets contributing the elements of life on Earth would
have great meaning for those searching for life on other planets, as well.

"It is so interdisciplinary, physics with organic chemistry with planetary
science all under the umbrella of exploring life's origins," explained
Blank. The building blocks of life, the essential molecules that form the
basis of everything from bacteria to brain surgeons, are either local
creations or imports from meteors or comets.

In the 1950s, two University of Chicago scientists did several experiments
suggesting these fundamentals were formed when lightning spurred chemical
reactions in the Earth's warm, chemically rich early atmosphere. The result
of this process was aptly called the primordial soup.

It turns out the process might not be quite that simple.

In the half century since that groundbreaking experiment, geologists have
disputed whether the Earth's atmosphere was either as warm or as chemically
rich as researchers originally believed. It might not have been able to
create the cell essentials, like sugars and amino acids.

So some far-out thinkers have turned to the stars.

Researchers already knew these particles were found in outer space and would
have hitched a ride on the comets that, in the more volatile early days,
regularly smashed into the Earth. But most scientists assumed that life's
somewhat-fragile essentials wouldn't survive the crash landing -- and the
2,000-degree temperatures such landings created.

That is, until Blank's big-gun experiments proved otherwise.

It turns out researchers ignored two vital elements -- pressure and time.

While high temperatures would tend to burn things up, immense pressures
would tend to hold them together. And while seconds-long hot stretches might
burn some molecules up, many can survive a short-term scorching fairly
unscathed.

Copyright (c) 2002, Sentinel Communications Co

===========
(5) (VERY SLOW) COLLISION MAY HAVE CHANGED THE WORLD

Tibet Cooled The World

http://www.abc.net.au/science/k2/moments/s485706.htm

Tibet is a spiritual place. It sits on the roof of the world - the 5 km high
Tibetan plateau. Some researchers now believe that this plateau cooled the
whole planet, and maybe helped the evolution of the human brain.

Now the climate of the world has been fairly predictable over most of the
last few hundred million years. Until recently, it was warm and wet, like
the tropics. Back then, the level of carbon dioxide was twice the level that
it is today. The dinosaurs, who lived from 200 million to 65 million years
ago, enjoyed a temperature about 8-11Co warmer, and swam in seas about half
a metre higher than we do today.

But all this changed 50 million years ago when India collided with Asia at
the frightening speed of 20 centimetres per year (roughly 4 times faster
than your fingernails grow). As a result of this slow but gigantic
collision, the Himalayas and Tibet relentlessly and gradually rose above
sea-level as India ploughed northwards another 2,000 km. India slowed its
northward speed to a more sedate 5 cm per year.

During this enormous collision, the Antarctic began to ice up and the world
cooled down. The world's temperature kept on dropping. About 2-3 million
years ago, our human brain began to double in size from 600 ml to about
1,200 ml.

It could be just a coincidence, but Big Brains do need a lot of cooling.
After all, we humans really need our big brains. We can't see very clearly,
we can't run very fast, our skin won't even stand up to a rose bush and our
nails are pathetic as claws. Compared to the other animals on the planet,
our big brain is our only worthwhile asset. But while our brain weighs only
2% of our body weight, it takes 20% of our blood supply, and so 20% of our
waste heat gets dumped from our head.

Now a new theory claims that the Tibetan Plateau is responsible for cooling
the world by taking carbon dioxide out of the air. The Tibetan Plateau is a
huge area, roughly half the size of Australia, and mostly higher than 5 km
above sea level. Clouds run into this plateau, and dump their water as rain.
In fact, the Tibetan plateau causes the annual Asian monsoons. As a result,
eight huge rivers, which include the Ganges, Mekong, Indus and the Yangtze,
drain from the Tibetan Plateau and its approaches. These rivers drain a
total area of less than 5% of
our Earth's land area, but they dump 25% of the minerals that reach the
ocean.

The very heavy rains combined with enormously steep slopes cause huge
erosion. The carbon dioxide that is dissolved in the rain drops forms a weak
acid - carbonic acid. This carbonic acid combines with granite and limestone
which come from the massive erosion. The combination of carbon dioxide and
granite/limestone makes minerals which wash downhill towards the ocean.
These minerals are very rich in carbon. So Tibet takes carbon dioxide out of
the atmosphere, and shoves it not into trees, but into minerals.

So, according to this theory, the Tibetan plateau is really a huge pump that
takes carbon dioxide out of the atmosphere, and deposits it on the ocean
floor where it stays locked away for millions of year.

The Tibet theory was created by oceanographer Maureen Raymo from MIT and her
colleague Bill Ruddiman, a paleoclimatologist of the University of Virginia.
They claim that chemical reactions caused by the Tibetan plateau have
removed so much carbon dioxide from the atmosphere, that the temperature has
dropped - not the Greenhouse Effect but the Tibetan Ice Block Effect.

Now the theory is in its early days, and it's not rock solid, but we do know
that after about 50 million years of a steady downward drop in both
temperature and carbon dioxide levels, the Earth's climate seems to have
stabilised into an oscillating series of Ice Ages and non-Ice Ages. And at
the end of that drop, our brains began to evolve larger. So maybe Tibet not
only chilled out the world, it also gave us swollen heads.

Karl S. Kruszelnicki Pty Ltd 2002.


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