[meteorite-list] Research Study Determines Life-Producing Phosphorus Was Carried To Earth By Meteorites

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 4 Jun 2013 15:33:30 -0700 (PDT)
Message-ID: <201306042233.r54MXUBR001958_at_zagami.jpl.nasa.gov>

http://news.usf.edu/article/templates/?a=5477&z=210

Solving a 3.5 Billion-Year-Old Mystery

A USF researcher is part of a team that determined life-producing phosphorus
was carried to Earth by meteorites.
 
By Vickie Chachere
University of South Florida
June 3, 2013
 
TAMPA, Fla. - Scientists may not know for certain whether life exists
in outer space, but new research from a team of scientists led by a University
of South Florida astrobiologist now shows that one key element that produced
life on Earth was carried here on meteorites.

In an article published in the new edition of the Proceedings of the National
Academies of Sciences, USF Assistant Professor of Geology Matthew Pasek
and researchers from the University of Washington and the Edinburg Centre
for Carbon Innovation, revealed new findings that explain how the reactive
phosphorus that was an essential component for creating the earliest life
forms came to Earth.

The scientists found that during the Hadean and Archean eons - the first
of the four principal eons of the Earth's earliest history - the heavy
bombardment of meteorites provided reactive phosphorus that when released
in water could be incorporated into prebiotic molecules. The scientists
documented the phosphorus in early Archean limestone, showing it was abundant
some 3.5 billion years ago.

The scientists concluded that the meteorites delivered phosphorus in minerals
that are not seen on the surface of the Earth, and these minerals corroded
in water to release phosphorus in a form seen only on the early Earth.
 
The discovery answers one of the key questions for scientist trying to
unlock the processes that gave rise to early life forms: Why don't we
see new life forms today?

"Meteorite phosphorus may have been a fuel that provided the energy and
phosphorus necessary for the onset of life," said Pasek, who studies the
chemical composition of space and how it might have contributed to the
origins of life. "If this meteoritic phosphorus is added to simple organic
compounds, it can generate phosphorus biomolecules identical to those
seen in life today."

Pasek said the research provides a plausible answer: The conditions under
which life arose on the Earth billions of years ago are no longer present
today.

"The present research shows that this is indeed the case: Phosphorus chemistry
on the early Earth was substantially different billions of years ago than
it is today," he added.

The research team reached their conclusion after examining Earth core
samples from Australia, Zimbabwe, West Virginia, Wyoming and in Avon Park,
Florida

Previous research had showed that before the emergence of modern DNA-RNA-protein
life that is known today, the earliest biological forms evolved from RNA
alone. What has stumped scientists, however, was understanding how those
early RNA-based life forms synthesized environmental phosphorus, which
in its current form is relatively insoluble and unreactive.

Meteorites would have provided reactive phosphorus in the form of the
iron-nickel phosphide mineral schreibersite, which in water released soluble
and reactive phosphite. Phosphite is the salt scientists believe could
have been incorporated into prebiotic molecules.

Of all of the samples analyzed, only the oldest, the Coonterunah carbonate
samples from the early Archean of Australia, showed the presence of phosphite,
Other natural sources of phosphite include lightning strikes, geothermal
fluids and possibly microbial activity under extremely anaerobic condition,
but no other terrestrial sources of phosphite have been identified and
none could have produced the quantities of phosphite needed to be dissolved
in early Earth oceans that gave rise to life, the researchers concluded.
 
The scientists said meteorite phosphite would have been abundant enough
to adjust the chemistry of the oceans, with its chemical signature later
becoming trapped in marine carbonate where it was preserved.

It is still possible, the researchers noted, that other natural sources
of phosphite could be identified, such as in hydrothermal systems. While
that might lead to reducing the total meteoric mass necessary to provide
enough phosphite, the researchers said more work would need to be done
to determine the exact contribution of separate sources to what they are
certain was an essential ingredient to early life.
Received on Tue 04 Jun 2013 06:33:30 PM PDT