[meteorite-list] Paleontologist Presents Origin of Life Theory

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 29 Oct 2013 14:07:24 -0700 (PDT)
Message-ID: <201310292107.r9TL7ORh024104_at_zagami.jpl.nasa.gov>

http://today.ttu.edu/2013/10/paleontologist-presents-origin-of-life-theory/

Paleontologist Presents Origin of Life Theory

Sankar Chatterjee presents what he calls the "Holy Grail of science" to
Geological Society of America.

Written by John Davis
Texas Tech Today
October 29, 2013

It has baffled humans for millennia: how did life begin on planet Earth?
Now, new research from a Texas Tech University paleontologist suggests
it may have rained from the skies and started in the bowels of hell.

Sankar Chatterjee, Horn Professor of Geosciences and curator of paleontology
at the Museum of Texas Tech University believes he has found the answer
by connecting theories on chemical evolution with evidence related to
our planet's early geology.

"This is bigger than finding any dinosaur," Chatterjee said. "This is
what we've all searched for - the Holy Grail of science."

Thanks to regular and heavy comet and meteorite bombardment of Earth's
surface during its formative years 4 billion years ago, the large craters
left behind not only contained water and the basic chemical building blocks
for life, but also became the perfect crucible to concentrate and cook
these chemicals to create the first simple organisms.

He will present his findings Oct. 30 during the 125th Anniversary Annual
Meeting of the Geological Society of America in Denver.

As well as discovering how ancient animals flew, Chatterjee discovered
the Shiva Meteorite Crater, which was created by a 25-mile-wide meteorite
that struck off the coast of India. This research concluded this giant
meteorite wreaked havoc simultaneously with the Chicxulub meteorite strike
near Mexico, finishing the dinosaurs 65 million years ago.

Ironically, Chatterjee's latest research suggests meteorites can be givers
of life as well as takers. He said that meteor and comet strikes likely
brought the ingredients and created the right conditions for life on our
planet. By studying three sites containing the world's oldest fossils,
he believes he knows how the first single-celled organisms formed in hydrothermal
crater basins.

"When the Earth formed some 4.5 billion years ago, it was a sterile planet
inhospitable to living organisms," Chatterjee said. "It was a seething
cauldron of erupting volcanoes, raining meteors and hot, noxious gasses.
One billion years later, it was a placid, watery planet teeming with microbial
life - the ancestors to all living things."

Recipe for Living

As the basins filled, volcanically driven geothermal vents heated the
water and created convection. The result was constant water movement,
creating a thick primordial soup.

For many years, the debate on the origins of life centered on the chemical
evolution of living cells from organic molecules by natural processes.
Chatterjee said life began in four steps of increasing complexity - cosmic,
geological, chemical and biological.

In the cosmic stage, a still-forming Earth and our solar system took a
daily pounding from rocky asteroids and icy comets between 4.1 to 3.8
billion years ago. Plate tectonics, wind and water have hidden evidence
of this early onslaught on our planet, but ancient craters on the surfaces
of Mars, Venus, Mercury and our moon show just how heavy the meteorite
showers once were.

Larger meteorites that created impact basins of about 350 miles in diameter
inadvertently became the perfect crucibles, he said. These meteorites
also punched through the Earth's crust, creating volcanically driven geothermal
vents. Also, they brought the basic building blocks of life that could
be concentrated and polymerized in the crater basins.

After studying the environments of the oldest fossil-containing rocks
on Earth in Greenland, Australia and South Africa, Chatterjee said these
could be remnants of ancient craters and may be the very spots where life
began in deep, dark and hot environments.

Because of Earth's perfect proximity to the sun, the comets that crashed
here melted into water and filled these basins with water and more ingredients.
This gave rise to the geological stage. As these basins filled, geothermal
venting heated the water and created convection, causing the water to
move constantly and create a thick primordial soup.

"The geological stage provides special dark, hot, and isolated environments
of the crater basins with the hydrothermal vent systems that served as
incubators for life," he said. "Segregation and concentration of organic
molecules by convective currents took place here, something like the kinds
we find on the ocean floor, but still very different. It was a bizarre
and isolated world that would seem like a vision of hell with the foul
smells of hydrogen sulfide, methane, nitric oxide and steam that provided
life-sustaining energy."

Then began the chemical stage, Chatterjee said. The heat churning the
water inside the craters mixed chemicals together and caused simple compounds
to grow into larger, more complex ones.
 
Eventually, the first life forms left the confines of the crater and ventured
into the newly formed oceans.

Protecting Important Information

Most likely, pores and crevices on the crater basins acted as scaffolds
for concentrations of simple RNA and protein molecules, he said. Unlike
a popular theory that believes RNA came first and proteins followed, Chatterjee
believes RNA and proteins emerged simultaneously and were encapsulated
and protected from the environment.

"The dual origin of the 'RNA/protein' world is more plausible in the vent
environments than the popular 'RNA world,'" he said. "RNA molecules are
very unstable. In vent environments, they would decompose quickly. Some
catalysts, such as simple proteins, were necessary for primitive RNA to
replicate and metabolize. On the other hand, amino acids, from which proteins
are made, are easier to make than RNA components."

The question remains how loose RNA and protein material floating in this
soup protected itself in a membrane. Chatterjee believes University of
California professor David Deamer's hypothesis that membranous material
existed in the primordial soup. Deamer isolated fatty acid vesicles from
the Murchison meteorite that fell in 1969 in Australia. The cosmic fatty
bubbles extracted from the meteorite mimic cell membranes.

"Meteorites brought this fatty lipid material to early Earth," Chatterjee
said. "This fatty lipid material floated on top of the water surface of
crater basins but moved to the bottom by convection currents. At some
point in this process during the course of millions of years, this fatty
membrane could have encapsulated simple RNA and proteins together like
a soap bubble. The RNA and protein molecules begin interacting and communicating.
Eventually RNA gave way to DNA - a much more stable compound - and with
the development of the genetic code, the first cells divided."

The final stage - the biological stage - represents the origin of replicating
cells as they began to store, process and transmit genetic information
to their daughter cells, Chatterjee said. Infinite combinations took place,
and countless numbers must have failed to function before the secret of
replication was broken and the proper selection occurred.

"These self-sustaining first cells were capable of Darwinian evolution,"
he said. "The emergence of the first cells on the early Earth was the
culmination of a long history of prior chemical, geological and cosmic
processes."

Chatterjee also believes that modern RNA-viruses and protein-rich prions
that cause deadly diseases probably represent the evolutionary legacy
of primitive RNA and protein molecules. They may be the oldest cellular
particles that predated the first cellular life. Once cellular life evolved,
RNA-viruses and prions became redundant, but survived as parasites on
the living cells.

The problem with theories on the origins of life is that they don't propose
any experiments that lead to the emergence of cells, Chatterjee said.
However, he suggested an experiment to recreate the ancient prebiotic
world and support or refute his theory.

"If future experiments with membrane-bound RNA viruses and prions result
in the creation of a synthetic protocell, it may reflect the plausible
pathways for the emergence of life on early Earth," he said.
Received on Tue 29 Oct 2013 05:07:24 PM PDT