George
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 Posted: Wed Oct 08, 2008 6:40 pm Post subject: Deep biosphere research points to new methods for recovering |
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http://www.eurekalert.org/pub_releases/2008-10/asu-dbr100708.php
Miles below us, deep within Earth>s crust, life is astir. Organisms there
are not the large creatures typically envisioned when thinking of life.
Instead, thriving there are microbes, the smallest and oldest form of life
on Earth. Although the biological diversity of these deep biosphere
microorganisms may surpass that of the more familiar surface biosphere, much
about them is still unknown, including the origin of the organic compounds
they consume. Arizona State University researchers are using a novel
approach that integrates physical organic chemistry with organic
geochemistry and biogeochemistry to uncover the source of these organic
compounds.
Carbon, the building block of organic matter, is one of the most dynamic
elements on the planet; it responds to biological, physical and chemical
processes in many ways and on many timescales. Understanding how carbon is
formed, where it comes from, and how much of it exists, is important for a
more detailed and coherent picture of the global carbon cycle. Yet a
complete understanding of how carbon is produced and consumed in the
environment still evades researchers because much of what is known is based
on processes that act on short time-scales and at Earth>s surface.
Deep biosphere microbes, like any living organism, require energy to
survive; for many, their sustenance comes in the form of organic compounds.
Over time, organic compounds are buried and pushed deeper into the Earth>s
crust. Harsh conditions on the journey to the deep Earth cause the organic
compounds to become "recalcitrant," meaning they are no longer in a form
that microbes can use. Some of the consumable organic compounds are produced
by other subsurface microbes, but a large portion is most likely the end
product of a mysterious geochemical process.
Theoretical biogeochemist Everett Shock, a professor in ASU>s School of
Earth and Space Exploration and the Department of Chemistry and Biochemistry
in the College of Liberal Arts and Sciences, leads an interdisciplinary
group of researchers who are investigating how this geochemical
transformation from recalcitrant matter to usable organic compounds occurs
deep in Earth>s crust.
"The secret appears to lie in how temperature and pressure affect the
reactivity of organic compounds, and, maybe more importantly, how the
properties of water change deep in sediments and sedimentary rocks," says
Shock. "The transformation in how water behaves is so enormous that we would
hardly recognize it as the same stuff that comes out of our kitchen taps."
Most organic reactions at the Earth>s surface do not work very well in
water; either they need an organism that has evolved the mechanisms to
promote organic reactions in water or they need an organic solvent, hexane
or benzene, for example. The very deep Earth, below where microbial life has
been shown to exist, has lots of rocks but no organic solvents. It does,
however, have very hot water.
Hilairy Hartnett, an assistant professor in the School of Earth and Space
Exploration and ASU>s Department of Chemistry and Biochemistry, is part of
Shock>s interdisciplinary group examining the mechanisms of the sub-surface
carbon cycle. The team hypothesizes that conditions deep in the Earth might
be good for complex organic reactions.
"Evidence suggests that hot water at high pressures - conditions we>d find
in the subsurface - is actually a very good solvent for organic reactions,"
Hartnett says. "It might be possible for these reactions to occur without
biology if the conditions are right." She explains, "Biological processes
can promote reactions to generate complex organic molecules even at
unfavorable low temperatures and pressures - the difference for the deep
Earth is the high-temperature and pressure."
Spurred by a $1.5M grant from the National Science Foundation, the team will
apply new theoretical models of how water at high temperatures and pressures
can transform organic compounds in unexpected ways. Through a series of
high-temperature/pressure experiments involving organic compounds, water,
and common minerals found in sedimentary rocks such as iron oxides and
clays, the team plans to reveal how organic transformation reactions occur
in natural geologic conditions.
Team member John Holloway, emeritus faculty in the School of Earth and Space
Exploration and ASU>s Department of Chemistry and Biochemistry, designed and
built the hydrothermal reaction vessels necessary for testing. At ASU>s new
Omni-pressure Lab, simple compounds such as water and carbon dioxide are
placed in the inert gold capsules and then tested.
"The samples are held at temperatures up to 300 degrees Celsius and
pressures of 250 atmospheres, equivalent to the bottom of the ocean (2,500
meters) or slightly higher, for periods of hours to weeks," explains
Holloway. "They are then quenched to ambient conditions and we analyze the
products using gas chromatography and mass-spectrometry."
The results of past similar experiments have shown that the concentration,
variety, and complexity of compounds all increase with time, and are
strongly influenced by contact with minerals during the experiments.
"It will be important to find out if the mixture of compounds we make in the
lab looks anything like the organic compounds that are found in the deep
subsurface," says Hartnett. "If they do, then maybe this is how they
formed - just rocks, hot water and simple carbon compounds. If they don>t,
well, we need to figure out what else is required."
"Lots of researchers have looked at individual aspects of the questions
we>re asking, but this is one of the first - or maybe the first - attempt to
look at these high-temperature water-rock-organic processes from an
integrated experimental and theoretical standpoint," Hartnett says.
A project of this caliber requires a team with a wide-range of expertise
from thermodynamic modeling, reaction mechanisms, and organic
characterization, to clay minerals and high-temperature/pressure
experiments. Many different techniques and backgrounds are necessary to
understand the complexities of the process.
"Some of the known organic reactions under hydrothermal conditions are
fascinating to me as an organic chemist. But this is a not a research field
that I can enter in my own, I don>t know how to do the experiments and I
don>t know which are the important observations," says chemistry professor
Ian Gould, "but I can bring expertise in the area of choosing useful and
informative reactions to study."
"No one person is an expert in all aspects of the project. As a team, we all
think about the same questions, but we each bring a different set of skills
and ideas to the forum. That often means we can find answers more quickly,
or find answers that come from a direction any one of us by ourselves might
have overlooked," says Hartnett.
"What we>re learning may be applied to hydrocarbon exploration, carbon
dioxide sequestration, environmental reclamation, and microbial
sustainability," says team member Lynda Williams, an associate research
professor in the School of Earth and Space Exploration who focuses on the
chemical composition of clay and sedimentary minerals. "It could also lead
toward understanding primordial conditions on Earth and similar planets
where carbon-based life has evolved," she adds.
This interdisciplinary approach to exploring organic reactions in hot water
may also have important implications for "green" chemistry. By learning more
about how to promote organic reactions in hot water, other researchers may
be able to take that knowledge and develop new chemical processes that don>t
have to use environmentally unfriendly, toxic solvents.
Funded through NSF>s Emerging Topics in Biogeochemical Cycles program, Shock
and his team will be the first to link organic geochemical reactions deep in
the Earth>s crust to the support of microbes in the deep biosphere. In the
process, the researchers plan to test new ideas about how petroleum forms
from deeply buried organic matter, including the direct involvement of deep
biosphere microbes. That deeply buried organic material is the precursor to
petroleum, but it may also be the food that many microbes need to survive.
"By understanding organic synthesis reactions in the deep biosphere, we may
find better organic and inorganic tracers to aid in finding petroleum
resources and recovering them in more environmentally friendly ways," says
Williams. |
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John Curtis
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| Posted: Thu Oct 09, 2008 3:05 pm Post subject: Re: Deep biosphere research points to new methods for recove |
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On Oct 8, 6:40 am, "George" <Geo...@george.net> wrote:
[quote]http://www.eurekalert.org/pub_releases/2008-10/asu-dbr100708.php
Carbon, the building block of organic matter, is one of the most dynamic
elements on the planet; it responds to biological, physical and chemical
processes in many ways and on many timescales.
Of equal significance is hydrogen, the most abundant element in the[/quote]
universe and the most abundant component of primordial substances,
as in Jupiter: H2, CH4, NH3, H2O, PH3, H2S, AsH3, GeH4.
Urey-Miller chose the first four primordials because of their
greatest
abundance, excluding helium:
http://en.wikipedia.org/wiki/Miller-Urey_experiment
Since life>s elements are selected from the first 30 atomic numbers,
additional hydrides could be included in the experiments.
John Curtis |
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