by Gilbert V. Levin
The view from Viking.
Labeled Release experiment on the Viking mission
positive results, although most have
as inorganic chemical reactions...
We humans can now peer back into the virtual origin of our universe.
We have learned much
about the laws of nature that control its seemingly infinite
celestial bodies, their evolution, motions and possible fate.
Yet, equally remarkable,
we have no generally accepted information as to whether other life
exists beyond us, or whether we are, as was
Samuel Coleridge's Ancient Mariner,
"alone, alone, all,
all alone, alone on a wide wide sea!"
We have made only one
exploration to solve that primal mystery.
I was fortunate to have
participated in that historic adventure as experimenter of the
Labeled Release (LR)
life detection experiment on NASA's spectacular
Viking mission to Mars in 1976.
On July 30, 1976, the LR returned its initial results from Mars.
Amazingly, they were
As the experiment
progressed, a total of four positive results, supported by five
varied controls, streamed down from the twin Viking spacecraft
landed some 4,000 miles apart.
The data curves signaled
the detection of microbial respiration on the Red Planet. The curves
from Mars were similar to those produced by LR tests of soils on
It seemed we had answered
that ultimate question.
When the Viking Molecular Analysis Experiment failed to
detect organic matter, the essence of life, however, NASA concluded
that the LR had found a substance mimicking life, but not
Inexplicably, over the 43
years since Viking, none of NASA's subsequent Mars landers
has carried a life detection instrument to follow up on these
Instead the agency
launched a series of missions to Mars to determine whether there
was ever a habitat suitable for life and, if so, eventually to
bring samples to Earth for biological examination.
NASA maintains the
search for alien life among its highest priorities.
On February 13, 2019,
NASA Administrator Jim Bridenstine said we might find
microbial life on Mars. Our nation has now committed to sending
astronauts to Mars. Any life there might threaten them, and us upon
Thus, the issue of
on Mars is now front and center.
Life on Mars seemed a
On the other hand, it
would take a near miracle for Mars to be sterile.
NASA scientist Chris
McKay once said that Mars and Earth have been "swapping spit"
for billions of years, meaning that, when either planet is hit by
comets or large meteorites, some ejecta shoot into space.
A tiny fraction of this
material eventually lands on the other planet, perhaps infecting
it with microbiological hitch-hikers. That some Earth microbial
species could survive the Martian environment has been demonstrated
in many laboratories.
There are even reports of
the survival of microorganisms exposed to naked space outside the
International Space Station (ISS).
NASA's reservation against a direct search for microorganisms
ignores the simplicity of the task accomplished by Louis Pasteur
in 1864. He allowed microbes to contaminate a hay-infusion broth,
after which bubbles of their expired gas appeared. Prior to
containing living microorganisms, no bubbles appeared.
(Pasteur had earlier
determined that heating, or pasteurizing, such a substance would
kill the microbes.)
This elegantly simple
test, updated to substitute modern microbial nutrients with the
hay-infusion products in Pasteur's, is in daily use by health
authorities around the world to examine potable water. Billions of
people are thus protected against microbial pathogens.
This standard test, in essence, was the LR test on Mars,
modified by the addition of several nutrients thought to broaden the
prospects for success with alien organisms, and the tagging of the
nutrients with radioactive carbon.
These enhancements made
the LR sensitive to the very low microbial populations postulated
for Mars, should any be there, and reduced the time for detection of
terrestrial microorganisms to about one hour.
But on Mars, each LR
experiment continued for seven days.
A heat control,
similar to Pasteur's, was added to determine whether any
response obtained was biological or chemical.
The Viking LR sought to detect and monitor ongoing metabolism, a
very simple and fail-proof indicator of living microorganisms.
Several thousand runs
were made, both before and after Viking, with terrestrial soils
and microbial cultures, both in the laboratory and in extreme
No false positive or
false negative result was ever obtained.
This strongly supports
the reliability of the LR Mars data, even though their
interpretation is debated.
In her recent book
To Mars with Love, my LR
co-experimenter Patricia Ann Straat provides much of the
scientific detail of the Viking LR at lay level.
published about the LR are available
on my Web site.
In addition to the direct evidence for life on Mars obtained by the
Viking LR, evidence supportive of, or consistent with, extant
microbial life on Mars has been obtained by Viking, subsequent
missions to Mars, and discoveries on Earth:
Surface water sufficient to
sustain microorganisms was found on Mars by,
activation of the Martian surface material did not, as
initially proposed, cause the LR reaction: a sample taken
from under a UV-shielding rock was as LR-active as surface
have been reported on Mars by Curiosity's scientists,
kerogen, which could be of
and Curiosity found evidence that the ancient Martian
environment may have been habitable
The excess of
carbon-13 over carbon-12 in the Martian atmosphere is
indicative of biological activity, which prefers ingesting
atmosphere is in disequilibrium:
should long ago have been converted to CO by the sun's
UV light; thus the CO2 is being regenerated,
possibly by microorganisms as on Earth
microorganisms have survived in outer space outside the ISS
viable microbes have likely been arriving on Mars from Earth
Methane has been
measured in the Martian atmosphere; microbial
methanogens could be the
disappearance of methane from the Martian atmosphere
requires a sink, possibly supplied by
methanotrophs that could
co-exist with methanogens on the Martian surface
will-O'-the-wisps on Earth
that are formed by spontaneous ignition of methane, have
been video-recorded on the Martian surface
ammonia, each possibly indicative of biology, are claimed to
be in the Martian atmosphere
complexity analysis of the positive LR signal identified it
spectral analyses by Viking's imaging system found
terrestrial lichen and green patches on Mars rocks to have
the identical color, saturation, hue and intensity
feature was in an image taken by Curiosity
stromatolites (formed by
microorganisms) were found by Curiosity; a statistical
analysis of their complex features showed less than a 0.04
percent probability that the similarity was caused by chance
inimical to life has been found on Mars
In summary, we have:
from a widely-used microbiological test
responses from strong and varied controls
the LR results at each of the two Viking sites
the experiment at the two sites
the failure over
43 years of any experiment or theory to provide a definitive
non-biological explanation of the Viking LR results
What is the evidence against the possibility of life on Mars?
The astonishing fact is
that there is none.
studies have shown that some terrestrial microorganisms could
survive and grow on Mars.
NASA has already announced that its 2020 Mars lander will
not contain a life-detection test. In keeping with
well-established scientific protocol, I believe an effort should be
made to put life detection experiments on the next Mars mission
I and my co-experimenter
have formally and informally proposed that the LR experiment,
amended with an ability to detect chiral metabolism, be sent to Mars
to confirm the existence of life:
chemical reactions do not distinguish between "left-handed" and
"right-handed" organic molecules, but all living things do.
Moreover, the Chiral
LR (CLR) could confirm and extend the Viking LR findings.
It could determine
whether any life detected were similar to ours, or whether there was
a separate genesis. This would be a fundamental scientific discovery
in its own right.
A small, lightweight CLR
has already been designed and its principle verified by tests. It
could readily be turned into a flight instrument.
Meanwhile a panel of expert scientists should review all pertinent
data of the Viking LR together with other and more recent evidence
concerning life on Mars.
Such an objective
jury might conclude, as I did, that the Viking LR did
In any event, the study
would likely produce important guidance for NASA's pursuit of its