The following post was posted to sci.astro. It's a long post the basic argument of which is that a recently discovered microbe may provide a biological explanation for the Viking life experiment results.
Of the three Viking life experiments, no biological explanation had been offered for one of them the Gas Exchange Experiment. The results of this experiment showed oxygen to be evolved in the dark. For Earth microbes, oxygen had been known to be produced as a product of photosynthesis which requires light. However, the recently discovered microbes do have just this capability to evolve oxygen in the dark.
I also suggest the experiments in the Atacama that sought to replicate the Labeled Release experiment results without biology may also have been detecting this species of microbe.


Bob Clark


From: "Robert Clark" <rgregoryclark>
Newsgroups: sci.astro,alt.sci.planetary,sci.chem,sci.physics,s ci.bio.misc
Subject: Possibilities for life on Mars - a surprising new microbe.
Date: Sat, 22 Jan 2005 01:25:58 -0800

The famous Viking life experiments provided perplexing results in
regard to life on Mars. They gave "positive" indications but they were
different from the ones expected for Earth life. Because a separate
experiment designed to detect organic molecules called the gas
chromatograph-mass spectrometer (GCMS) was unable to detect any
organics, the accepted conclusion in regard to the life experiments was
that it was exotic chemistry not biology that caused the unusual
reactions.
However, the Principal Investigator for one of the experiments Dr. Gil
Levin still believes his experiment called the Labeled Release
Experiment did in fact detect life on Mars [1],[2],[3]. There have been
several attempts to explain the biology experiment results by chemistry
alone, usually by invoking oxidants: see the Science article [4] and
the references contained therein (also see Levin's response following
it). All such explanations have difficulties explaining all three
experiments. Levin believes biology is at least as simple an
explanation as the various combinations of oxidants required to explain
all three experiments.
The three biology experiments were the Labeled Release Experiment, the
Pyrolytic Release Experiment, and the Gas Exchange Experiment. The NASA
report [5] available online has a summary of these experiments. The
book "The Search for Life on Mars" [6] provides a detailed review of
the life experiments and the opinions of the scientists involved in the
Viking mission. Levin believes his experimental results do mimic
results he's seen with Earth life at low numbers of microbes (other
scientists dispute this.) The Pyrolitic Release positive indications
could also be explained by low numbers of microbes, on the order of a
few thousand per gram. Note that normal Earth soils typically contain
billions of microbes per gram.
However, in regards to a life explanation the Gas Exchange Experiment
offers a puzzle. It detects life by evolution of oxygen and carbon
dioxide. Both of these were observed but again in small amounts.
However, what is really curious about the GEx is that the oxygen
evolution occurred in the dark. There were no known examples of
microbes that evolved oxygen in the dark. The usual way microbes evolve
oxygen is through photosynthesis which of course requires light.
However, recently there has been discovered a microbe with just this
capability to evolve oxygen in the dark [7],[8],[9],[10]:

Presto! Bacteria Turn Toxic Wastes into Salt Component and Oxygen.
"A research team has discovered a variety of bacteria that can break
down certain toxic wastes into a component of ordinary table salt and
other harmless chemicals. As an added bonus, the microbes can be made
to produce oxygen as a by-product of the breakdown process, meaning
this may be a new source of that essential, life-giving, breathable
gas."
...
"If these bacteria exist all over the place and they naturally break
down toxic wastes such as perchlorate, why then is perchlorate
pollution a problem anywhere? Well, in some cases, the microbes are
breaking down these toxic wastes without any help from us. But the
reason it's not happening at a faster pace all over is that the right
carbon sources are often lacking, Achenbach and Coates explain. Carbon
sources are like food for the bacteria. By adding acetate
or other cheap carbon sources to soil or water targeted for cleanup,
the researchers were able to kick the bacteria's natural toxic waste
degrading abilities into high gear."[7]


Newly Discovered Bacteria Can Generate Oxygen.
"A diverse group of bugs, they all share a trait unique in the
microbial world: Given the right kind of 'food,' they will crank out
oxygen.
"An organism that in the absence of air can produce oxygen got us to
thinking about possible applications - - and there are many,' said
microbial physiologist John D. Coates, who heads one of two SIUC
research teams studying the bacteria.
"Among others, they could supply air tanks for deep-sea diving or
long-distance space travel, and because oxygen inhibits the growth of
the agent that causes gas gangrene, they could be used to develop the
first-ever field treatment for deep-wound injuries' - - all
possibilities for which Coates has applied for patents."[8]


BENZENE BUSTERS.
"The newly discovered microbes, bacteria known as Dechloromonas strain
RCB and Dechloromonas strain JJ, degrade benzene to carbon dioxide
anaerobically—that is, without oxygen. (Most bacteria are aerobic,
needing oxygen to live.)
...
"When contamination occurs, such as an oil spill or chemical tank leak,
aerobic bacteria start breaking down the pollutants—but they often
get stopped in their tracks because they use up all the available
oxygen. Coates’s lab previously had isolated several Dechloromonas
species capable of breaking down chlorite (another pollutant) and
giving off oxygen, a rare feat for microbes. That oxygen production can
fuel aerobic bacteria to continue their cleanup work."[9]


BREATH OF LIFE.
Fated to Exhale
"Despite their diversity, these organisms share the same highly
specialized metabolism. They take in chlorate for respiration and use
certain forms of organic carbon as food. They convert the chlorate to
chlorite, another toxic compound, which they then break apart into
oxygen and chloride. They use the oxygen molecules to help process the
carbon, and they dump the chloride, a benign waste product.
In essence, says Coates, the bacteria "breathe in chlorate and breathe
out chloride.'
"Chlorate-using bacteria are now being used to treat
chlorate-contaminated wastes, such as rocket fuel wastes and wastes
from pulp and paper mills. But the patent applications Coates has filed
rest on another unusual characteristic of these microbes.'
"About three years ago, researchers in the Netherlands working with the
first known chlorate-using species discovered something interesting. If
they withheld carbon and chlorate, but supplied chlorite, the bacteria
still would break down the chlorite. But, since the bacteria had no
carbon to process, they gave off both oxygen and chloride as
byproducts."
...
"In lab experiments at SIUC, it took less than 10 seconds for a
population of chlorate-using bacteria to produce oxygen from
chlorite."[10]

This last fact about these new microbes is also relevant to the Viking
experiments because part of the reason for doubting the biological
origin of the positive life results was that the gases were evolved so
quickly that they were thought to be the result of chemistry.
A recent experiment on Earth may provide a means of testing the
likelihood of these microbes for providing a match for the Viking life
results [11]. The experiment attempted to replicate the Labeled Release
experiment results using samples from the Atacama desert in Chile. The
experimenters took samples from different parts of the desert with
varying moisture contents. They found they were able to get a response
from the experiment both in the (relatively) wetter areas as well in
the driest areas.
In the wetter areas they were able to find detectable microbes from
DNA tests. However, in the driest areas they were not able to find
detectable microbes even though the Labeled Release analogue gave a
positive response. They concluded that the LRx positive response could
not be due to life in these driest areas. However, curiosly they were
able to detect organics in these samples using a device analogous to
the Viking GCMS, though at levels below that which the Viking GCMS
could have detected them.
As with Mars, the scientists concluded oxidants must be the origin of
the positive responses. However, they were not able to identify this
chemical oxidant. This is curious. The oxidants proposed for Mars were
all pretty simple inorganic compounds. That it couldn't be identified
suggests a more complex compound, which may in fact be organic. But
this would be in conflict with the *interpretation* of no organics on
Mars.
The other possibility that yet remains is that it could be microbes
that caused these responses in the Atacama samples - perhaps the newly
discovered oxygen-evolving microbes. One factor that suggests it could
be is because of a curious fact in the geochemistry of Atacama: it is
one of the only, if not the only, places known to have large natural
deposits of perchlorate.
Scientists Coates and Achenbach found the oxygen-evolving microbes to
be ubiquitous wherever they looked, including the extremely dry desert
of Antarctica [12],[13]. Since the microbes feed on perchlorates and
Atacama has large deposits of perchlorate, they are very likely to be
found there as well.
Note though that the Labeled Release experiment detects evolved carbon
dioxide, not oxygen. However, interestingly some strains of the microbe
can convert benzene to carbon dioxide [9],[13] and benzene was indeed
found in the samples from the driest areas of Atacama.
But the Atacama experimenters did not find DNA in their samples from
the driest areas. However, they used the method of PCR to detect DNA.
This requires the use of a primer to generate recognizable DNA. If you
use the wrong primer you won't generate detectable DNA [14]:

Genetic Regulation of Perchlorate Reduction.
"In order to track (per)chlorate-reducing bacteria in the environment,
we have designed primer sets specific to the most predominant groups of
perchlorate reducers in the environment. However, due to the extreme
phylogenetic diversity of perchlorate-reducing bacteria, 16S ribosomal
RNA primer sets can only be designed to detect a few specific genera of
(per)chlorate-reducing bacteria in the environment (e.g. Dechloromonas
and Dechlorosoma). A more inclusive approach for the detection of
bacteria capable of (per)chlorate reduction is to develop a metabolic
gene probe. We were recently the first to sequence and genetically
characterize a novel gene involved in (per)chlorate reduction, the gene
for chlorite dismutase."[14]

Coates and Achenbach have developed a genetic probe for the presence
of their oxygen-evolving bacteria [15],[16]. I recommend using these
tests to determine if the microbe is present in the Atacama samples.
Another method that might determine if the Atacama results were due to
biology is an idea developed by Lin Chao. He notes that life has the
ability to evolve when exposed to new environments. He suggests
successively transferring the putative life forms to a new nutrient
batch and observing whether or not they become more efficient at
utilizing the nutrients, in essence a test to see if they undergo
natural selection and Darwinian evolution [17],[18].

If microbes were present in the Martian soil, why did the GCMS not
detect the required organic compounds? Recent experiments show that
millions of microbes per gram could be contained in soil without the
Viking GCMS being able to detect them:

State-of-the-art instruments for detecting extraterrestrial life.
"The possible presence of organic compounds on Mars is also uncertain.
Using a pyrolysis procedure, in combination with a gas
chromatograph/mass spectrometer (GCMS), Viking did not detect any
organic compounds above a level of a few parts per billion in near
surface samples at two different landing sites. However, it is now
apparent that the Viking pyrolysis GCMS instruments would not have
detected the presence of millions of bacterial cells in 1 g of soil. In
addition, oxidation reactions involving organic compounds on the
Martian surface would likely produce nonvolatile products that also
would not have been detected by the Viking GCMS."[19]

In addition to this, there may have been another factor operating: the
GCMS may not have received samples of sufficient size to register a
response. The GCMS as designed was supposed to give a signal indicating
that full samples were delivered. This signal was never received
[20],[21]:

ON MARS.
Ch. 11-5 SCIENCE ON MARS.
"The first soil samples were acquired on sol 8, 28
July. Four samples were dug, with the first being
deposited into the biology instrument distributor
assembly, the next two into the GCMS processor, and
the fourth into the funnel of the x-ray fluorescence
spectrometer. All the commands were successfully
executed, but there was no positive indication that the
gas chromatograph-mass spectrometer processor
had been properly filled. A second acquisition attempt
still did not provide a "sample level detector `full'
indication". The sampler system, having completed its
programmed sequences in a normal manner, parked the boom
as planned. On Earth, the lander performance specialists
began to analyze the possible causes of the anomaly: (1)
insufficient sample acquired in the collector head
because the same sample collection
site had also been used for the biology sample; (2)
insufficient time allowed for the sample to pass from the
funnel through the sample grinding section and then
through the fine (300-micrometer) sieve into the metering
cavity of the instrument; (3) grinder stirring spring not
contacting the sieve; or (4) sample-level-detector
circuit faulty. Since the "level-full" detector
consisted of a very fine wire stretched across the cavity
to which the sample material was
delivered, it was also possible that it had broken when
the soil was dropped into the funnel."[20]

and

The Search for Organic Substances and Inorganic Volatile
Compounds in the Surface of Mars.
"The are two positions to which any of the ovens
can be moved in any sequence. The load position is
directly under the sampling system, which delivers about
1-2 cm^3 of surface material that after having been
ground is passed through a 0.3 mm sieve. A mechanical
poker pushes the material through a funnel into the oven.
This operation is timed in such a manner that the filling
of the oven is complete with any of the terrestrial test
soils (including finely ground basalt, commonly referred
to as 'lunar nominal'). However, there is no sensor
measuring the final level or completeness of the fulling
operation. Thus one has to assume that the oven is filled
to capacity, i.e., approximately 60 mm^3 of surface
material is being analyzed."[21]

So it is possible the GCMS only got a partial sample
delivered. This obviously could effect the "no organics on Mars"
conclusion from the GCMS experiment.
In contrast, the biology experiments, which used the same delivery
system as the GCMS, did get their sample "full" indications. It turns
out that the GCMS used a much smaller sieving grid for its samples then
the biology experiments. Then a possible explanation is that some grain
sizes were larger than the grid for the GCMS which caused it too clog.
An additional factor is the electrostatic charging that should take
place in the dry thin atmosphere on Mars, which could have caused
particles to adhere to the grid. In fact the Pathfinder mission found
electrostatic adhesion of the magnetic dust on Mars to the Sojourner
wheels. An experiment I would like to see performed would be to see if
using Mars soil simulants in dry, low pressure, cold conditions as on
Mars if only small amounts of sample are passed through because of
electrostatic adhesion.
Mars scientists in examining the GCMS results came to the conclusion
that samples were delivered because water was detected in the
experiment. However, it is impossible to know the size of the samples
delivered. It could still be that the samples were so small that
organics in the sample did not register.
This is important because the amount of water assumed to be in the
Martian soil is based on this measurement. However, two separate
measurement techniques suggest this amount is too low, one from
Earth-bound infrared spectra of Mars, the other from the gamma-ray
spectrometer experiment on Mars Odyssey. The first comes from a paper
[22] that shows there is a discrepancy between the water content of the
Martian soil as determined by the GCMS and determined by other
Earth-based and orbiter observations, perhaps by a factor of 1 to 2
orders of magnitude. The second is from the GRS measurements showing
large amounts of water in the Martian surface [23]:

Mars Water, Odd Surface Features Tied to Life.
"Data gleaned by Odyssey has shown tremendous water ice deposits,
Boynton said.
"It really is changing the way we think of how the ice formed,"
Boynton told SPACE.com . The idea that water vapor eked down to depths
deep enough and cold enough to condense out does not seem to account
for the vast amounts of water ice detected, he said.
"There's no telling how deep the ice might extend just below surface on
Mars, Boynton said. It could be several hundreds of feet to well over a
mile in depth.
"All of a sudden you're starting to talk about a pretty significant
amount of water," Boynton said. "It looks like the Viking 2 landing
site was actually right on top of this ice. If its robot arm had dug
just a little bit deeper they would have found it,' he said."[23]

Boynton assumes here that the discrepancy was due to the Viking sample
arm not going deep enough, but actually it may be because the Viking
measurement was off.


Bob Clark


1.)Proceedings of Spie, SPIE-The International Society for Optical
Engineering, "Instruments, Methods, and Missions for the Investigation
of Extraterrestrial Microorganisms."
29 July-1 August 1997, San Diego, California
The Viking Labeled Release Experiment and Life on Mars
Gilbert V. Levin
Biospherics Incorporated
http://mars.spherix.com/spie/spiehtml.htm

2.)Liquid water and life on Mars.
Gilbert V. Levin and Ron L. Levin
http://mars.spherix.com/spie2/spie98.htm

3.)Mars : the living planet.
Barry DiGregorio; Gilbert V Levin; Patricia Ann Straat
Publisher: Berkeley, Calif. : Frog, c1997.
http://www.amazon.com/exec/obidos/ISBN=1883319587/

4.)Evidence That the Reactivity of the Martian Soil Is Due to
Superoxide Ions.
A. S. Yen, S. S. Kim, M. H. Hecht, M. S. Frant, B. Murray
Science, Vol 289, Issue 5486, 1909-1912 , 15 September 2000
http://www.sciencemag.org/cgi/conten.../289/5486/1909

5.)SP-4212
On Mars: Exploration of the Red Planet. 1958-1978.
SCIENCE ON MARS.
http://www.hq.nasa.gov/office/pao/Hi...12/ch11-5.html

6.)The search for life on Mars : evolution of an idea.
Henry S. F. Cooper, Jr.
New York : Holt, Rinehart and Winston, c1980.
http://www.amazon.com/exec/obidos/ISBN=0030461669/

7.)Presto! Bacteria Turn Toxic Wastes into Salt Component and Oxygen.
http://www.microbe.org/news/perchlorate_microbe.asp

8.)Newly Discovered Bacteria Can Generate Oxygen.
http://www.siu.edu/backissues/001004/

9.)BENZENE BUSTERS
http://www.siu.edu/~perspect/01_fall/benzene.html

10.)BREATH OF LIFE.
http://www.siu.edu/worda/persp/f98/Breath.html

11.)Mars-Like Soils in the Atacama Desert, Chile, and the Dry Limit of
Microbial Life.
Science, Vol 302, Issue 5647, 1018-1021 , 7 November 2003
http://www.sciencemag.org/cgi/conten.../302/5647/1018

12.)Ubiquity and Diversity of Dissimilatory (Per)chlorate-Reducing
Bacteria.
Applied and Environmental Microbiology, December 1999, p. 5234-5241,
Vol. 65, No. 12
http://aem.asm.org/cgi/content/full/65/12/5234

13.)Anaerobic benzene oxidation coupled to nitrate reduction in pure
culture by two strains of Dechloromonas.
NATURE |VOL 411 | 28 JUNE 2001 |1039-1043
http://www.nature.com/nature/journal...df/4111039.pdf

14.)Laurie A. Achenbach
Research Interests.
Genetic Regulation of Perchlorate Reduction.
http://www.science.siu.edu/microbiology/achenbach/

15.)Universal Immunoprobe for (Per)Chlorate-Reducing Bacteria.
Applied and Environmental Microbiology, June 2002, p. 3108-3113, Vol.
68, No. 6
http://aem.asm.org/cgi/content/full/68/6/3108

16.)Sequencing and Transcriptional Analysis of the Chlorite Dismutase
Gene of Dechloromonas agitata and Its Use as a Metabolic Probe.
Applied and Environmental Microbiology, October 2002, p. 4820-4826,
Vol. 68, No. 10
http://aem.asm.org/cgi/content/full/68/10/4820

17.)Defining Life
by Bruce Moomaw
Cameron Park - April 28, 2000
http://spacedaily.com/news/life-00w4.html

18.)The Meaning of Life.
by Lin Chao
BioScience, March 2000, Vol. 50, No. 3, p. 245-250.
http://ibscore.dbs.umt.edu/biol223/B...eads/Chao2.pdf

19.)State-of-the-art instruments for detecting extraterrestrial life.
Jeffrey L. Bada
PNAS | January 30, 2001 | vol. 98 | no. 3 | 797-800
http://www.pnas.org/cgi/content/full/98/3/797

20.)ON MARS.
Ch. 11-5 SCIENCE ON MARS
http://www.hq.nasa.gov/office/pao/Hi...12/ch11-5.html

21.)The Search for Organic Substances and Inorganic Volatile
Compounds in the Surface of Mars, Jour. Geophys. Res.,
vol. 82, no. 28, September 30, 1977, p. 4642.

22.)Water content of the Martian soil: Laboratory simulations of
reflectance spectra,
Authors: YEN, A. S.; MURRAY, B. C.; ROSSMAN, G. R.,
Journal: Journal of Geophysical Research, v. 103, No. E5, p. 11,125
(1998).
http://www.gps.caltech.edu/~marssurf/waterice/soilh2o/

23.)Mars Water, Odd Surface Features Tied to Life.
By Leonard David
Senior Space Writer
28 March 2003
http://space.com/scienceastronomy/ma...ks_030328.html

The problem with the Viking experiments was that Viking landed in a locatin where life probably should not have been expected near the surface (even if life does exist on Mars).

So even a negative result doesn't seem very final to me.

We need to run new experiments at more interesting locations (near possible thermal features and near the edges of the polar caps), which are spots that are technically difficult for landings and are not close to the equator making solar panels inefficient.