[meteorite-list] NASA Study Suggest Giant Space Clouds Iced Earth

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Mar 21 13:24:53 2005
Message-ID: <200503041824.j24IOO928708_at_zagami.jpl.nasa.gov>

Gretchen Cook-Anderson
Headquarters, Washington March 3, 2005
(Phone: 202/358-0836)

John Bluck
Ames Research Center, Moffett Field, Calif.
(Phone: 650/604-5026/9000)

Jim Scott
University of Colorado, Boulder
(Phone: 303/492-3114)

RELEASE: 05-066

NASA STUDY SUGGESTS GIANT SPACE CLOUDS ICED EARTH

Eons ago, giant clouds in space may have led to global
extinctions, according to two recent technical papers
supported by NASA's Astrobiology Institute.

One paper outlines a rare scenario in which Earth iced
over during snowball glaciations, after the solar system
passed through dense space clouds. In a more likely
scenario, less dense giant molecular clouds may have
enabled charged particles to enter Earth's atmosphere,
leading to destruction of much of the planet's protective
ozone layer. This resulted in global extinctions,
according to the second paper. Both recently appeared in
the Geophysical Research Letters.

"Computer models show dramatic climate change can be
caused by interstellar dust accumulating in Earth's
atmosphere during the solar system's immersion into a
dense space cloud," said Alex Pavlov, principal author
of the two papers. He is a scientist at the University
of Colorado, Boulder. The resulting dust layer hovering
over the Earth would absorb and scatter solar radiation,
yet allow heat to escape from the planet into space,
causing runaway ice buildup and snowball glaciations.

"There are indications from 600 to 800 million years ago;
at least two of four glaciations were snowball glaciations.
The big mystery revolves around how they are triggered,"
Pavlov said. He concluded the snowball glaciations
covered the entire Earth.

Pavlov said this hypothesis has to be tested by geologists.
They would look at Earth's rocks to find layers that relate
to the snowball glaciations to assess whether uranium 235 is
present in higher amounts. It cannot be produced naturally on
Earth or in the solar system, but it is constantly produced
in space clouds by exploding stars called supernovae.

Sudden, small changes in the uranium 235/238-ratio in rock
layers would be proof interstellar material is present that
originated from supernovae. Collisions of the solar system
with dense space clouds are rare, but according to Pavlov's
research, more frequent solar system collisions, with
moderately dense space clouds, can be devastating. He
outlined a complex series of events that would result in
loss of much of Earth's protective ozone layer, if the solar
system collided with a moderately dense space cloud.

The research outlined a scenario that begins as Earth passes
through a moderately dense space cloud that cannot compress
the outer edge of the sun's heliosphere into a region within
the Earth's orbit. The heliosphere is the expanse that begins
at the sun's surface and usually reaches far past the orbits
of the planets. Because it remains beyond Earth's orbit, the
heliosphere continues to deflect dust particles away from the
planet.

However, because of the large flow of hydrogen from space
clouds into the sun's heliosphere, the sun greatly increases
its production of electrically charged cosmic rays from the
hydrogen particles. This also increases the flow of cosmic
rays towards Earth. Normally, Earth's magnetic field and
ozone layer protect life from cosmic rays and the sun's
dangerous ultraviolet radiation.

Moderately dense space clouds are huge, and the solar system
could take as long as 500,000 years to cross one of them.
Once in such a cloud, the Earth would be expected to undergo
at least one magnetic reversal. During a reversal, electrically
charged cosmic rays can enter Earth's atmosphere instead of
being deflected by the planet's magnetic field.

Cosmic rays can fly into the atmosphere and break up nitrogen
molecules to form nitrogen oxides. Nitrogen oxide catalysts
would set off the destruction of as much as 40 percent of
the protective ozone in the planet's upper atmosphere across
the globe and destruction of about 80 percent of the ozone
over the polar regions according to Pavlov.

For information about NASA and agency programs on the Internet,
visit:

http://www.nasa.gov


-end-
Received on Fri 04 Mar 2005 01:24:24 PM PST