[meteorite-list] 'Lost' Miller Experiment Gives Pungent Clue to Origin of Life

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 24 Mar 2011 14:57:39 -0700 (PDT)
Message-ID: <201103242157.p2OLvdV1013737_at_zagami.jpl.nasa.gov>

http://www.nasa.gov/centers/goddard/news/releases/2011/lost_exp.html

"Lost" Miller Experiment Gives Pungent Clue to Origin of Life
March 23, 2011

Goddard Release No. 11-23

Nancy Neal-Jones / Bill Steigerwald
NASA's Goddard Space Flight Center, Greenbelt, Md.
301-286-0039 / 5017
Nancy.N.Jones at nasa.gov
William.A.Steigerwald at nasa.gov
 
GREENBELT, Md. -- The origin of life may have been smelly, according to
a recent, NASA-funded analysis of residue from a variant of classic
experiments performed by Dr. Stanley Miller in the 1950s.

"One of the primary differences between this experiment and others
Miller performed is the use of hydrogen sulfide (H2S) gas to help
simulate the primordial atmosphere," said Eric Parker of the Georgia
Institute of Technology, Atlanta, Ga. Hydrogen sulfide gas is commonly
known as the awful smell released by rotten eggs. Parker is lead author
of a paper on this research appearing the week of March 21 in the
on-line Early Edition of the Proceedings of the National Academy of
Sciences.

"Much to our surprise, the yield of amino acids from Miller's hydrogen
sulfide experiment is a lot richer than that from any other experiment
he had ever conducted," said Professor Jeffrey Bada of the Scripps
Institution of Oceanography, University of California at San Diego, who
was a graduate student of Miller's and is the corresponding author on
the paper.

>From 1953 to 1954, Stanley Miller, then a graduate student at the
University of Chicago, performed a series of experiments with colleague
Harold Urey using a system of closed flasks containing water and a
mixture of simple gases. At the time the gases used in the experiment
(hydrogen, methane, and ammonia) were thought to be common in Earth's
ancient atmosphere.

The gas was zapped with an electric spark. After running the experiment
for a few days, the water turned brown. When Miller analyzed the water,
he found it contained amino acids, which are the building blocks of
proteins -- life's toolkit -- used in everything from structures like
hair and nails to processes that speed up, facilitate, and regulate
chemical reactions. The spark provided energy for the gas molecules to
recombine into compounds such as hydrogen cyanide, aldehydes, and
ketones, which rained out into the water. There these compounds further
reacted in the presence of ammonia to produce amino acids.

Miller's experiment showed how simple molecules could be assembled into
the more complex molecules necessary for life by natural processes, like
lightning in Earth's ancient atmosphere.

After Miller's death in 2007, Bada discovered vials containing samples
from the original experiments. In 2008, Bada and his team, which
consisted of NASA and university researchers, analyzed these samples
with modern equipment to see if they could discover chemicals that could
not be detected with the techniques of the 1950s. The samples were
produced by a variant of Miller's classic design that introduced a jet
of steam to simulate conditions in the cloud from an erupting volcano.
In October 2008, the team reported
<http://www.nasa.gov/centers/goddard/news/topstory/2008/volcanic_life_origin.html>
that they discovered 22 amino acids in the sample, 10 of which had never
been found in any other experiment like this.

In the new research, the team analyzed samples from another variant of
the experiment performed in 1958 in which Miller used carbon dioxide and
hydrogen sulfide gas in the mixture. It was "lost" for decades because,
for unknown reasons, Miller never reported his analysis of the results.
"Stanley mentioned to several of us that he hated working with hydrogen
sulfide because it smelled so bad and tended to make him sick," says
Bada. "Given that some of the compounds he made in the experiment smell
pretty bad, this experiment may be the basis for his reluctance to deal
with H2S in experiments."

The team discovered that the experiment created amino acids containing
sulfur, the first such synthesis from a simulated prebiotic environment,
according to Parker, and the one that produced them in the greatest
diversity and highest abundance.

"The sulfur-containing amino acids we found include significant
biological ones like methionine, the product of the 'start codon' in the
genetic code, which tells a cell's machinery to begin translating the
design for a protein," said Dr. H. James Cleaves of the Carnegie
Institution of Washington, a co-author who performed some of the
analyses in collaboration with scientists in the Analytical Astrobiology
Laboratory at NASA's Goddard Space Flight Center in Greenbelt, Md.

"The results of this study may provide clues about the roles that
primordial volcanic plumes may have played in the formation of some of
Earth's first organic compounds," adds Parker. "Volcanoes are a natural
source of atmospheric H2S. Lightning events are often observed to
coincide with volcanic eruptions. The use of H2S in this experiment,
along with the other gases Miller used, combined with the spark
discharge implemented, simulating lightning, may provide a model for
what early volcanic plumes could have been composed of. The results
indicate that volcanic areas on the primitive Earth may have been
responsible for the localized production of large quantities and
varieties of prebiotic compounds on ancient Earth."

The team at Goddard has analyzed many carbon-rich meteorites, and found
amino acids in them as well, suggesting that biologically important
molecules could have been made in space and delivered to ancient Earth
by meteorite impacts, assisting the origin of life with a supply of
ready-made parts.

"We found that the types and abundances of amino acids produced in
Miller's hydrogen sulfide experiment more closely match what we find in
carbon-rich meteorites, the so-called carbonaceous chondrites," says Dr.
Jason Dworkin of NASA Goddard, a co-author on the paper and Chief of
Goddard's Astrochemistry laboratory.

The closer match is significant, because the atmosphere Miller simulated
in the hydrogen sulfide experiment more closely resembles what
geoscientists now think Earth's early atmosphere may have been like,
according to Parker. Instead of being heavily laden with hydrogen,
methane, and ammonia, many scientists now believe Earth's ancient
atmosphere was mostly carbon dioxide, carbon monoxide, and nitrogen with
traces of other gases like hydrogen sulfide, methane, and ammonia.

"The results of this experiment suggest that a mixture of oxidized and
reduced compounds, including hydrogen sulfide, may have been important
in the formation of amino acids and amines not only on Earth, but
elsewhere, namely inside the parent bodies of meteorites," says Parker.

The research was funded by the NASA Astrobiology Institute, managed by
NASA's Ames Research Center, Moffett Field, Calif.; the Goddard Center
for Astrobiology, and the NASA Postdoctoral Program. Dworkin and Cleaves
were also graduate students of Miller's. Parker, now a graduate student
at Georgia Tech, led the study. Co-authors include H. James Cleaves from
the Geophysical Laboratory at the Carnegie Institution of Washington in
Washington D.C.; Jason P. Dworkin, Daniel P. Glavin, and Michael P.
Callahan of NASA Goddard Andrew D. Aubrey of NASA's Jet Propulsion
Laboratory, California Institute of Technology, Pasadena, Calif., and
Antonio Lazcano of the National Autonomous University of Mexico in
Mexico City.
 
Received on Thu 24 Mar 2011 05:57:39 PM PDT