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Posted by baalke on February 27, 2007, 1:51 pm
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http://www.jpl.nasa.gov/news/features.cfm?feature=1290
Sensor Being Developed to Check for Life on Mars
Jet Propulsion Laboratory
February 26, 2007
NASA-funded researchers are refining a tool that could not only check
for the faintest traces of life's molecular building blocks on Mars,
but
could also determine whether they have been produced by anything
alive.
The instrument, called Urey: Mars Organic and Oxidant Detector, has
already shown its capabilities in one of the most barren climes on
Earth, the Atacama Desert in Chile. The European Space Agency has
chosen
this tool from the United States as part of the science payload for
the
ExoMars rover planned for launch in 2013. Last month, NASA selected
Urey
for an instrument-development investment of $750,000.
The European Space Agency plans for the ExoMars rover to grind samples
of Martian soil to fine powder and deliver them to a suite of
analytical
instruments, including Urey, that will search for signs of life. Each
sample will be a spoonful of material dug from underground by a
robotic
drill.
"Urey will be able to detect key molecules associated with life at a
sensitivity roughly a million times greater than previous
instrumentation," said Dr. Jeffrey Bada of Scripps Institution of
Oceanography at the University of California, San Diego. Bada is the
principal investigator for an international team of scientists and
engineers working on various components of the device.
To aid in interpreting that information, part of the tool would assess
how rapidly the environmental conditions on Mars erase those molecular
clues.
Dr. Pascale Ehrenfreund of the University of Leiden in the
Netherlands,
said, "The main objective of ExoMars is to search for life. Urey will
be
a key instrument for that because it is the one with the highest
sensitivity for organic chemicals." Ehrenfreund, one of two deputy
principal investigators for Urey, coordinates efforts of team members
from five other European countries.
Urey can detect several types of organic molecules, such as amino
acids,
at concentrations as low as a few parts per trillion.
All life on Earth assembles chains of amino acids to make proteins.
However, amino acids can be made either by a living organism or by
non-biological means. This means it is possible that Mars has amino
acids and other chemical precursors of life but has never had life. To
distinguish between that situation and evidence for past or present
life
on Mars, the Urey instrument team will make use of the knowledge that
most types of amino acids can exist in two different forms. One form
is
referred to as "left-handed" and the other as "right-handed." Just as
the right hand on a human mirrors the left, these two forms of an
amino
acid mirror each other.
Amino acids from a non-biological source come in a roughly 50-50 mix
of
right-handed and left-handed forms. Life on Earth, from the simplest
microbes to the largest plants and animals, makes and uses only
left-handed amino acids, with rare exceptions. Comparable uniformity
--
either all left or all right -- is expected in any extraterrestrial
life
using building blocks that have mirror-image versions because a
mixture
would complicate biochemistry.
"The Urey instrument will be able to distinguish between left-handed
amino acids and right-handed ones," said Allen Farrington, Urey
project
manager at NASA's Jet Propulsion Laboratory, which will build the
instrument to be sent to Mars.
If Urey were to find an even mix of the mirror-image molecules on
Mars,
that would suggest life as we know it never began there. All-left or
all-right would be strong evidence that life now exists on Mars, with
all-right dramatically implying an origin separate from Earth life.
Something between 50-50 and uniformity could result if Martian life
once
existed, because amino acids created biologically gradually change
toward an even mixture in the absence of life.
The 1976 NASA Viking mission discovered that strongly oxidizing
conditions at the Martian surface complicate experiments to search for
life. The Urey instrument has a component, called the Mars oxidant
instrument, for examining those conditions.
---------------------------------------------------------------
NASA-BACKED TEAM DEVELOPING SENSOR TO CHECK FOR LIFE ON MARS
INSTRUMENT'S NAME PAYS TRIBUTE TO SCIENTIST
A 1953 experiment that involved making chemical building blocks of
life
was one major achievement of the scientist from whom the Urey
instrument
takes its name.
Dr. Harold Urey (1893-1981)
and Dr. Stanley Miller, while at the University of Chicago, simulated
a
hypothetical step in the evolution of life by using electric sparks to
convert a mixture of simpler ingredients -- water, ammonia, methane
and
hydrogen -- into amino acids and other organic chemicals.
Unlike the amino acids produced by living organisms, amino acids
produced by the Miller-Urey experiment and by other non-biological
reactions are an even mixture of right-handed and left-handed forms.
The
Urey instrument for Mars will use this difference to assess whether
any
amino acids found on Mars are evidence for life.
Harold Urey's long career included many accomplishments. He won the
Nobel Prize for Chemistry in 1934 for the discovery of deuterium, the
heavy isotope of hydrogen. Beginning in 1958, he helped build a strong
chemistry program at the University of California, San Diego, now the
home instruction of the principal investigator for the Urey
instrument,
Dr. Jeffrey Bada.
----------------------------------------------------------------------
The oxidant instrument has microsensors coated with various chemical
films. "By measuring the reaction of the sensor films with chemicals
present in the Martian soil and atmosphere, we can establish if
organisms could survive and if evidence of past life would be
preserved," said Dr. Richard Quinn, a co-investigator on Urey from the
SETI Institute, Mountain View, Calif., who also works at NASA Ames
Research Center, Moffett Field, Calif.
"In order to improve our chances of finding chemical evidence of life
on
Mars, and designing human habitats and other equipment that will
function well on Mars' surface, we need to improve our understanding
of
oxidants in the planet's surface environment," said Dr. Aaron Zent, a
Urey co-investigator at NASA Ames.
A Urey component called the sub-critical water extractor handles the
task of getting any organic compounds out of each powdered sample the
ExoMars rover delivers to the instrument. "It's like an espresso
maker,"
explained JPL's Dr. Frank Grunthaner, a deputy principal investigator
for Urey. "We bring the water with us. It is added to the sample, and
different types of organic compounds dissolve into the liquid as the
temperature increases. We keep it under pressure the whole time."
The dissolved compounds are highly concentrated by stripping away
water
in a tiny oven.
Then a detector checks for fluorescent glowing, which would indicate
the
presence of amino acids, some components of DNA and RNA, or other
organic compounds that bind to a fluorescing chemical added by the
instrument.
A Urey component called the micro-capillary electrophoresis unit has
the
critical job of separating different types of organic compounds from
one
another for identification, including separation of mirror-image amino
acids from each other. "We have essentially put a laboratory onto a
single wafer," said Dr. Richard Mathies of the University of
California,
Berkeley, a Urey co-investigator. The device for sending to Mars will
be
a small version incorporating this detection technology, which is
already in use for biomedical procedures such as law-enforcement DNA
tests and checking for hazardous microbes.
Switzerland will provide electronics design and packaging expertise
for
Urey. Micro-Cameras and Space Exploration S.A., Neuchatel, will
collaborate with JPL and the European Space Agency to accomplish this
significant contribution to the heart of the instrument. Dr. Jean-Luc
Josset, Urey co-investigator at the University of Neuchatel will
coordinate this effort and help provide detector selection and
support.
JPL is a division of the California Institute of Technology in
Pasadena.
------------------------------------------------------------------------
Media contacts: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
Dwayne Brown 202-358-1726
NASA Headquarters, Washington
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Posted by John Curtis on February 28, 2007, 6:56 pm
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On Feb 27, 10:51 am, baa...@earthlink.net wrote:
> http://www.jpl.nasa.gov/news/features.cfm?feature=1290
>
> A Urey component called the sub-critical water extractor handles the
> task of getting any organic compounds out of each powdered sample the
> ExoMars rover delivers to the instrument.
>
Sub-critical water and primordial (Urey-Miller type) gases are the
hallmarks of a black smoker:
http://www.pmel.noaa.gov/vents/chemistry/images/vents2.gif
Black smokers are invariably accompanied by living organisms
even before the chimney is formed:
http://www.marinetech.org/nine_degrees/index.php
Perhaps the sub-critical-water extractor could be tested against
Urey-Miller type gases to establish a baseline. John Curtis
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