Marsnow. info

Research published by Dr. Levin and Associates

MARS: Dead or Alive?


Gilbert V. Levin

Arizona State University


Patricia Ann Straat

NIH (Ret.)

Presented at

Mars Society Convention

League City, TX

August 8, 2014





Throughout the thousands of years since we Earthlings first became inquisitive, we have been taunted by the lugubrious question of whether or not we are alone in the universe.  It was not until 1976 that we developed the technology to launch the first direct search for extraterrestrial life.  That quest was the primary goal of NASA’s Viking Mission to Mars that landed two spacecraft on the surface of the red planet.  At both sites, the Labeled Release (LR) experiment obtained data that satisfied the pre-mission criteria for the detection of extant microbial life.  Ad hoc experiments performed by the LR on Mars, new information about the habitability of Mars, the finding of life in extreme environments on Earth, the similarity among the Viking LR responses and LR responses from some terrestrial viable soils, and the likelihood that the two planets cross-infect each other support that conclusion.  However, the Viking LR evidence was not generally accepted initially, and, to this day, while gaining credence, lacks the consensus of the scientific community.   NASA’s current position is that the LR results are, at best, ambiguous.  Inasmuch as the search for life remains the “Holy Grail” of NASA’s Astrobiology Program, means to resolve this issue are suggested, as is the significance of what may be achieved.


Primarily, herein is a narrative account of the Viking LR experiment: its thesis, development, execution, data, the reasons for their lack of acceptance, and relevant post-Viking findings. The status quo of the LR is presented as of the date of this writing, some 38 years after Viking landed, during which period, remarkably, NASA has not sent another life detection experiment to Mars.  Included in this paper are relevant reported results, as of the time of this writing, from the Mars Science Laboratory Mission, “Curiosity.”  The authors herein provide the evidence supporting their claim that the LR did discover living microorganisms on Mars.  A method is proposed that can validate the claim and begin a study of comparative biology. 



Since Viking, many new findings have added important information to provide a realistic background against which to view and evaluate the LR findings.  Microorganisms have been found living in extreme environments rivaling Mars.   Cryptoendolithic lichen, B. subtilis and B. pumilus have recently been reported[1],[2],[3] to have survived in naked space for 1.5 years, the full term of their exposure.  Microorganisms have been found[4] growing in perpetual ice at the South Polar Cap.  NASA missions have produced data leading to the conclusion[5] that large regions of Mars were habitable in the past.  The current diurnal temperatures[6],[7],[8] over wide areas of Mars rise well above freezing.  Perhaps most importantly for the life issue, liquid water has been measured[9] in amounts up to several percent in surface samples on Mars, amounts well above those in many areas of Earth heavily populated with microorganisms.   In all, it is likely that many forms of terrestrial life could survive some current environments on Mars.  It has also been deduced[10] and supported by laboratory experiments, that Earth and Mars have been seeding each other with ejecta from meteor and meteorite hits.  It has been proposed[11],[12] that microorganisms inside such ejecta from one planet could survive to arrive in viable form to infect the other, as depicted in Figure 1. 



FIG. 1.  Cross-Infection of Mars and Earth.


In a similar manner, either planet could be infected from other life-bearing sources.  Indeed, in view of the post-Viking information, it could be contended that it might be very difficult for Mars to be sterile.  Thus, this brief background is offered to “level the playing field” on which to view the possibility of life on Mars and, specifically, on which to interpret the LR experiment.        



In classic terms, the purpose of an experiment is to test a key prediction of a thesis put forth.   If the prediction is supported by the experiment, the thesis is accepted.  The thesis that there might be life on Mars existed for many years before the capability to test it was developed by NASA.  Twenty years of effort were then devoted to preparing carefully selected experiments.  Among these was the LR, originally called the “Radioisotopic Biochemical Probe for Extraterrestrial Life,” and then “Gulliver,” before being changed by NASA to the “Labeled Release” experiment when it was accepted as one of the Viking experiments.


The LR on Mars was a specific experiment designed to test only a narrowly defined critical aspect of the theory concerning the possibility of life on Mars.  The key elements of that restricted approach were: 1. there is life on Mars, because it is environmentally sufficiently similar to Earth, 2. as a minimum there is microbial life, because of its relative simplicity and the need for it to recycle any form of life for continuity, 3. the microbial life operates on a biochemistry similar to that on Earth, the only sample of life we have, and 4. the amount of available liquid water required for life is available there despite the apparent dryness of the planet. 


The other Viking life detection experiments were designed to test other specific hypotheses of possible forms of microbial life on Mars. The Gas Exchange (GEx) life detection experiment was designed to test for microbial life exposed at first to the addition of humidity only, and then to immersion in a “chicken soup” of organic nutrients and supplements.  The Pyrolytic Release (PR) experiment was designed to test for microorganisms that photosynthetically incorporated atmospheric CO2 and/or CO in a simulated Mars environment without any addition of water.   NASA said its selection of life detection experiments was designed to test different possibilities for life, and that, were there life on Mars, it would likely respond to only one of the experiments, if any.   



The LR thesis was based on the belief that early Mars and Earth possessed similar environments, each of which were subject to the natural production of Miller-Urey type organic compounds.  These compounds were then available for the genesis of life, participated in its evolution, and remain to participate in its metabolism today.  Therein lies the presumption of the similarity of the two planetary metabolisms.  The LR was planned to detect life by monitoring for this metabolism over a long period of time, rather than to seek a “biosignature,” or snapshot, of some particular life-indicating molecule.  Since life is the most complex substance we know, the detection of any biosignature molecule could suffer by the application of Occam’s Razor.  That discriminator of truth would conclude that the detected substance could more readily have evolved abiotically than to have required the genesis of life for its production.  Most biologists today believe that the progression of biological compounds had to arise abiotically to be incorporated into the genesis of life.


The LR married the use of Miller-Urey compounds with a simple and universally used test for microbial contamination of water or food, and introduced trace radioisotopes to enhance the sensitivity of the method.  That test[13] is still used by health authorities around the world in determining the presence of E. coli in a sample.  The Miller-Urey compounds were added to the nutrient solution to broaden its appeal to alien microbial species.  Then, all the compounds were tagged with 14C.  This enabled initial detection[14] of metabolism in about 30 minutes as opposed to the 48 to 72 hours required by the Standard Method for the generation of some 1.7 x 109 cells from an inoculum of one in order to produce a visible bubble of gas.  The likely sparse population of cells in the cold and dry Martian soil, and the precariousness of the landed spacecraft and its vulnerable communication with Earth made the sensitivity provided by the 14C highly advantageous. 


Final selection of the LR compounds was sodium formate, sodium lactate, glycine, alanine and calcium glycolate.  All are Miller-Urey compounds.  In addition, each was tested with a very broad range of microbial heterotrophs and phototrophs in soils, pure cultures and mixed cultures.  Several thousand tests were made during the development program.  In every case, where life was present, a positive response was obtained.  In some cases, classical methods used for comparison failed to respond while the more sensitive LR did respond.  However, the elimination of the LR response by application of the control measure showed that the sample had contained life. 


Inasmuch as the reason for the preferences of left-handed amino acids and right-handed carbohydrates by our form of life is unknown, it was originally proposed to send duplicate LR instruments so both handednesses could be offered separately in case the Martian life forms exhibited a different handedness from ours.  Weight and cost constraints prohibited this, so both left- and right-handed forms of those LR compounds that occur in isomeric forms were included in the nutrient.  In order to minimize the possibility of toxicity, the concentrations of these compounds were kept at only 2.5 x 10-4 molar each.   For the same reason, each of the 14C labeled compounds was kept at less than 12 uCi/ml, with each carbon uniformly labeled with 14C at 2 uCi/C.  Table 1 shows the makeup of the Viking LR nutrient solution.  It was assumed that any living organisms would be gaining all the supplements needed from the soil, so none was added.  Also, no buffer was used so as not to upset the prevailing pH.  Thus, every effort was made to treat any life present as gently as possible and merely to insinuate a revealing signal into its normal life process.  


 TABLE 1.  The Viking LR Nutrient Solution



Structure and

label position (*)




  µCi ML-1*

Specific Activity




14C-sodium formate

14C-DL-sodium lactate

14C-calcium glycolate






2.5 × 10-4M

5.0 × 10-4M

2.5 × 10-4M

5.0 × 10-4M

2.5 × 10-4M











*Total=34 (6.8 × 10-7 dpm ml-1)





In early application of the LR, several mg of a suspected sample were placed into 10 ml of 14C-labeled nutrient solution.  Air was bubbled through the solution and exited through a tube terminating in an open-ended holder containing a paper pad moistened with saturated BaOHsolution.  Any CO2 in the gas passing through the pad was trapped by the BaOH2.  Every 15 minutes the pad was replaced with a fresh one.  The pads so collected were then dried and counted for radioactivity.  The radioactivity was plotted cumulatively as a function of time.  The resulting curve showed the typical microbial lag phase before the on-start of the sharp rise attributed to exponential growth.  On one field trip, a single drop of the nutrient solution was placed directly on the ground.  The spot was immediately covered with an inverted planchet that contained a paper absorbent pad moistened with a saturated solution of BaOH2.   Every fifteen minutes the planchet was replaced with a fresh one containing a newly moistened pad.  When the planchets were dried and counted for radioactivity, it was surprising to see that no lag phase had occurred.  The response was immediate.  Figure 2 compares the “wet” and “moist” modes of performing the LR.  From then on, the moist mode was adopted. 



Fig. 2.  Comparison of “Wet” and “Moist” Modes of LR.


Not knowing what the optimum moisture content might be for Martian microorganisms, it was decided to inject a 0.115 ml dose of nutrient solution onto the center of approximately 0.5 cc of soil sample in the 3.5 cc cylindrical chamber with a 2 cm diameter.  In this way, chromatographic action provided a range of moisture content starting with liquid at the center and progressing to minimal moisture at the periphery of the sample.   Other environmental conditions chosen for the experiment were a temperature of 10o C ± 2o C, Martian atmosphere, a helium overpressure to 85 mb to assure liquidity in the event the Martian atmosphere were below the triple point, darkness, and a seven-sol test cycle.   The schematic for the LR instrument test cell is shown in Figure 3.   One major advantage of this simple experiment and instrument is that the signal appears in a gas phase, readily rising out of the liquid phase of the nutrient solution.  Thus, there is no problem in differentiating the signal from the radioactivity of the mother liquor.  This allows for full utilization of the extraordinary sensitivity of the radioisotope method.


FIG. 3.  Schematic of Labeled Release Test Chamber.


While the Standard Method does not require a control, it was felt that a control would be important for acceptance of the test performed under many unknown conditions on an alien planet.  Initially, the control used was a broad-spectrum antimetabolite, Bard-Parker Germicide.  When a positive response was obtained from a soil sample, a duplicate sample was treated with Bard-Parker solution and then tested by the LR method.  The germicide was potent enough to significantly reduce the response from viable soils or cultures.  No such reduction would indicate a chemical had been responsible for the initial positive response.  NASA decided the control was a good idea, but asked that it be changed to the application of heat rather than an antimetabolite, feeling the former was more universal and more likely to be effective on possible Martian life.  NASA proposed treating the control sample at 160o C for three hours, allowing it to cool and testing it in the LR instrument.  That control method was adopted.    


A paper[15] was published making the prediction for the experiment testing the theory for Martian life as seen in Figure 4.  The predicted LR test and control curves were based on testing of terrestrial soils and cultures as modified by then current knowledge of Martian environmental conditions. 


Fig. 4. Pre-Mission Predicted LR Response from Microbial Life on Mars.


Thus, in classical scientific fashion, the thesis and predicted outcome of an important experiment were in place. 



The experiment took some 20 years to develop and perform.  The first ten years were spent in developing and verifying the scientific method with the senior author as PI under contract from NASA to Spherix (originally “Biospherics”).  Based on the results, the method was chosen for inclusion in the Viking Mission from among many submitted to a NASA-designated national selection committee.   The senior author was named Experimenter when the Viking Mission was created and the LR chosen as a flight experiment.  The co-author then joined as Co-Experimenter.  There followed ten more years of improvement of the method, development of the instrument, testing, and manufacture of the flight instrument.  Over the entire twenty-year development period, the LR was performed thousands of times, on pure cultures, mixed cultures, heterotrophs, phototrophs and soils, many of which were provided by NASA from harsh environments around the world.  Field tests were also made in which working models of the instrument were taken to extreme environments, e.g.: Antarctica, White Mountain above timber line, Salton Sea flats, Death Valley sands, all of which responded positively.  Samples of naturally sterile soils (Moon, Surtsey, and one Antarctic sample) tested negative, showing the validity of LR in detecting sterile samples.  Not once in all these laboratory and field tests did the LR produce a false positive or false negative response when compared to standard methods by which it was checked.  On some occasions, the LR was positive and the standard method was negative.  In these cases, the LR control showed that the sample had contained living organisms not detected by the standard method.  By the time it was sent to Mars, the LR was completely vetted and merited a high degree of confidence.


The development of the Viking LR instrument was jointly performed under contracts to Spherix and TRW, Inc.  TRW constructed the actual flight hardware.  During the final phase, Dr. Straat lived near the TRW plant at Redondo Beach and worked with the engineers there to insure accuracy in conveying the science into the hardware.  A Test Standards Module (TSM) of the instrument, duplicating the critical flight parameters and experimental conditions, was constructed and operated at TRW and later moved to the NASA Ames Research Center.  Shown in Figure 5, this was used to test the various development stages of the experiment, and to facilitate their incorporation into the flight instrument. 



Fig. 5.  Labeled Release Test Standards Module. The Test Standards Module contains Labeled Release test cells, detectors, nutrient reservoir, valves, and heaters which are essentially identical to flight components. The instrument was operated by manual manipulation of the valves and heaters to perform an entire flight sequence. The location of the flight components is indicated by arrow in the left photograph. These components, enlarged in the right photograph, are covered during an experiment with a bell jar that was supplied with a simulated Martian atmosphere. The temperature of the test cell was   regulated to obtain isothermal or diurnal temperature patterns, as desired.


 TRW made a final test of the LR experiment on a California (“Aiken”) soil under Mars experiment conditions in a flight instrument called SN103.  This was performed to verify the fitness of the project, and for comparison with any possible Martian result.  Figure 6 presents the results from SN103 on California soil held for three days under Martian environmental conditions before the sample was inoculated. The results proved prophetic in magnitude to those obtained on Mars, as seen in Figure 8, although more of the gas emission occurred later in the active cycle than on Mars.


Fig. 6.  SN103 Results from California (“Aiken”) Soil Under Martian Conditions.


The flight instrument contained four incubation cells of 3.5 cc volume placed in a carousel that rotated such that each cell could be positioned to receive a soil sample delivered from the lander distribution box.  After sample reception, the LR culture chamber and the head end of the cell were pressed together with an intervening gold seal to prevent any gas leakage.  The counting chamber contained two solid state beta detectors.  Any gas evolved from the culture rose to the counting chamber through a narrow 13” tortuous tube which prevented any radioactive dust or aerosol raised by the injection of the nutrient solution from reaching the counting chamber.  The detectors measured the amount of radioactivity, hence gas, evolved in the culture chamber and rising into the counting chamber.  Measurements were made at an initial frequency of four minutes for two hours, and then every sixteen minutes for the rest of the test cycle.   The LR hardware contained all necessary plumbing, operated by eight miniaturized solenoid valves, to manipulate the liquid nutrient and gas components.  This included helium gas for purging the radioactive nutrient of any radioactive gas formed through self-degradation of the radioisotopes during the long journey from Earth.  The culture chamber also contained a heater and temperature sensors in the top head end for controlling and recording the temperature during the runs and during heat sterilization.   


The LR flight instrument had to fit into about a quarter of a cubic foot.  Figure 7 contains a diagram of the three Viking life detection instruments packaged together.  


Fig. 7. Viking Mission Life Detection and GCMS Instrument Packages.


The Vikings contained one additional instrument that turned out to be of overriding importance in interpreting the LR results.  It was the Molecular Analysis instrument that consisted of a gas chromatograph-mass spectrometer (GCMS) illustrated in Fig. 7.  Its function was to identify the organic compounds that were expected to have accumulated on Mars the same as they had on Earth. 


The LR on Mars  

Vikings 1 and 2 were launched August 20, and September 9, 1975, and landed safely on Mars July 20 and September 3, 1976, respectively.  


Viking 1

On July 30, 1976, sol 10, Viking 1 ran the first LR sample on Martian soil.  The sample was taken from soil that had been scooped up on sol eight by the sampling arm.  It consisted of surface material dredged to a depth of about four cm.  The sample had been stored in the distribution box at approximately 10o C for the two intervening sols.  The LR response was immediate and strongly positive.  After the run was complete, the critical control phase of the experiment was performed on a duplicate sample of the same soil.  The response was negative.  Figure 8 shows these initial Mars LR test and control results.  These results satisfied the pre-mission criteria accepted by NASA for the detection of life.








Fig. 8.  First Mars LR Test and Control Results.


However, doubts were cast when the experiment was continued past its seven-sol cycle, after which additional injections of nutrient failed to produce resurgences of gas, but, instead, caused immediate depletions in the headspace gas, as seen in Figure 9, VL1 cycle 1 extended. 


FIG. 9.  Effect of Second Injection of Nutrient on VL1 Cycle 1.


While a resurgence of gas would have been more assertive of biology, the observed effect could be attributed to death of the microorganisms and reabsorption of CO2 by the alkaline soil when wetted.  As seen in Figure 10, a NASA-bonded test soil, Antarctic 664, with a pH of 8.1, had acted similarly in the TSM when the LR nutrient dose was repeated.


FIG. 10.  Antarctic Soil 664 LR Response to Second Injection of Nutrient.


In keeping with scientific protocol to verify a positive result, the third run, VL1 cycle 3, was a duplicate of the first, but with a fresh sample of the soil taken from the same area as the first.  The response was positive, validating the first.  Second and third injections produced the same re-absorption of gas as seen with VL1 cycle 1.  The fourth and final LR run at Viking site 1 was a double injection on a sample from the same area that had produced the positive response in VL1 cycle 1.  However, at the time of the injection for this VL1 cycle 4 run, the soil had been stored in the distribution box, in the dark, open to the Martian atmosphere, at temperatures ranging between 10o C and 26o C for 141 sols.  Two nutrient injections were made, about three hours apart, in order to allow a response from the first before administering the second.  However, each injection resulted in a negative response.   Long-term storage of an active soil under modest environmental conditions had inactivated an initially active sample.  This raised the possibility that, isolated from their environment, microorganisms had perished during the storage period.  Since the soil had remained active after being held three days (in a previous  run) at approximately 10o C prior to first injection, it seems more difficult to propose a chemical that survived those conditions for two or three days, but not for the longer period.  If the loss of activity were simply a matter of something evaporating from the soil sample, that substance would likely have evaporated from the half cc sample during the three days it was held at approximately 10o C before injection. 


Isolated in a test tube and maintained at a temperature above freezing, a bacterial culture will lose all vitality over time as short as a month.  Hence, cultures are preserved by desiccating them and holding them at temperatures below the freezing point of water.  The sample held in the Viking distribution box was isolated from its natural environment.  Thus, possibly deprived of nutrients at temperatures above freezing, the organisms might have died.


All initial Viking site 1 test and control responses are shown in Figure 11.


FIG. 11.  All First Injection Cycles of VL1.   A fresh sample was used for the active sequences of cycles 1 and 3 whereas the sample used for active cycle 4 was stored for approximately 141 Sols at 10-26°C prior to use. For cycle 2, a stored portion of the same sample used for cycle 1 was heated for 3 hours at 160°C prior to nutrient injection. All data have been corrected for background counts observed prior to nutrient injection.


Despite duplication of the positive result, the negative control and the biological leaning of the storage data, doubt remained.  It increased greatly when the GCMS failed to detect any organic matter in the Martian soil or atmosphere. 


Viking 2

With the positive LR result duplicated at Viking site 1, the traditional scientific procedure was followed by attempting to replicate the entire experiment at Viking site 2, some 4,000 miles distant.  There, the first sample produced the positive response shown in Figure 12, essentially duplicating that of VL1 cycle 1. 


FIG. 12.  First LR Response at Viking 2 Site.


Since the VL1 LR 160o C control cycle results were not accepted as evidence that Martian life had been detected , a meeting of the Biology Team was called to discuss another control.  All Members agreed that, if a control sample heated to 50o C for three hours proved negative, it would be accepted as confirmation for the detection of life.  The engineers, responding to this appeal for an ad hoc experiment, attempted the 50o C heating, but they reported that the temperature achieved was 51o C.  This resulted in a peculiar response, VL2 cycle 2, consisting of a series of small, sharp spurts of gas over time, each spurt then being reabsorbed as in the case of repeated injections. Each small spurt showed kinetics similar to those produced by positive runs upon repeated injections, but on a much smaller scale.

FIG. 13.  VL2 Cycle 2 LR Response.


It seemed as if numerous attempts had been made to react with the nutrient, but each attempt quickly succumbed and the wetted alkaline soil then quickly absorbed the gas that had been emitted.  Added together, the pulses totaled only 10% of the amount of gas evolved in the positive response.  The demise of the active agent when heated to only 51o C for three hours seems more likely attributable to biology than to chemistry.  The possible biological attribution of the pulses adds to this likelihood.  The engineers checked the instrument for a possible intermittent gas leak to account for the loss of gas after each of the spikes.  They reported no problem, and, indeed, subsequent experiments worked well, supporting that there was no instrument problem.  The Team’s agreement notwithstanding, a biological origin of the positive result was still denied. 


It was then contended that the positive responses were attributable to “activation” of the soil by the intense flux of UV light impacting the surface of Mars.  The activated soil, it was contended, reacted with the nutrients yielding radioactive gas, a false positive for life.  Further discussion with the engineers made it possible to test this theory directly on Mars.  Just at dawn, the sampling arm moved a rock and obtained a sample that the rock had been shielding from UV light for eons.  After two days in the test cell, that sample, VL2 cycle 3, was tested.  It proved strongly positive, nearly as active as the previous positive samples, dispelling the UV theory. 


An attempt was then made to clarify the confusion instilled by the unique, sporadic response of VL2 cycle 2.  A fresh soil sample was heated, aiming for 50o C as before.  This time, however, the temperature attained was only 46o C.  The result was very different from that of the first attempt.  The LR VL2 cycle 4 response to this treated sample produced essentially the same kinetics as a positive sample, but with only about 30 percent of its amplitude.



FIG. 14.  VL2 Cycle 4 LR Response.


This engendered considerable discussion as to whether its origin was chemical or biological.  It was noted, however, that comparison of the 46o C and 51o C response curves is reminiscent of the 37o C v 44o C responses used to differentiate between E. coli and the coliform group.  Only the E. coli survive at 44o C.  It is possible that microorganisms in the Mars sample heated to 51o C primarily died, while at least some of those heated to only 46o C survived.  A chemical agent, displaying such a major change in sensitivity to a temperature difference of only 5o C is difficult to propose, and none has been put forth.


VL2 cycle 4 used the last of the LR culture chambers.  However, with nutrient solution still available, an additional run was improvised.  This would have to be done in a culture cell that already contained soil from a previous run.  At this point, the Martian winter approached Viking site 2, and sampling activity was halted for fear of damaging the sampling arm.   Rather than wait for spring, risking possible damage to the spacecraft or loss of communication, it was decided to re-test the active sample used for the VL2 cycle 3 that had, by then, been held in the sample distribution box for 84 sols at approximately 10o C.   As seen in Figure 15, showing all first injection VL2 responses, storage of the sample used for VL2 cycle 5 had inactivated the soil, producing a negative response. 

FIG. 15.  All First Injection VL2 LR Results.


Moreover, VL2 cycle 5 showed that, although the active agent remained active when held two sols at 10±2o C (VL2 cycle 3), it succumbed upon long-term storage at approximately 10o C.


Characteristics determined for the active agent discovered in the surface material of Mars are listed in Table 2.  All cycles of VL1 had two injections except cycle 3 that had three.  All cycles of VL2 had two injections except cycle 5 that had only one. 




















Characteristics of Active Agent Detected by Viking LR Experiment

  1. Produced positive response when inoculated with nutrient solution, similar in kinetics and amplitude to responses produced by LR test of a number of terrestrial viable soils.
  2. Inactivated upon heating to 160o C for three hours, similar to terrestrial tests of active soils.
  3. Heating to 51o C for three hours produced sporadic series of small responses, totaling approximately 10% of a positive response.
  4. Heating to 46o C for three hours produced response similar to positive response but reduced 70% in amplitude.
  5. Inactivated upon two months’ isolation in soil distribution box in dark at approximately 10o C.
  6. Activation of soil not caused by UV exposure.
    1. Added injection of nutrient solution to positively responding soil caused approximately 25% of gas already evolved to disappear from detector cell (probably re-adsorbed into soil), gradually to re-evolve.
      1. Positive responses from soils tested by a universally accepted microbiological method augmented to improve sensitivity and broaden appeal.
      2. The duplication of the Mars VL1 LR test data at Viking 1.
      3. Replication of Mars VL1 data at VL2 some 4,000 miles distant.
      4. Mars LR responses fall within range of responses from a variety of terrestrial microbes.
      5. Positive Viking LR responses were similar to the Mars simulation test SN103 performed on California soil.
      6. Negative response from the 160o control regimen approved by NASA to confirm the detection of life.
      7. Additional, ad hoc low temperature controls rendering a non-biological cause difficult, especially because of inactivation of the active agent upon sequestered storage.
        1. Failure of any scientifically sustainable experiment or theory, from the many tried or proposed over the past 38 years, to provide a non-biological explanation of the LR data.
        2. Odyssey’s finding of water ice or liquid water within several cm of the surface over wide expanses of Mars.
        3. The finding that the temperature of the atmosphere immediately above the surface of Mars frequently reaches the 20o C range, sufficient to provide liquid water from the near-surface ice.
        4. Acceptance of reasons for the failure of the Viking GCMS to detect organic matter.
        5. Death of terrestrial bacteria upon sequestered storage.
        6. The great expansion in knowledge of the terrestrial domain of life into extreme environments, some of which are as inhospitable as those at Viking 1 and 2 sites.
        7. The finding that Mars was habitable in the past, with no explicit reason that it is not still habitable.
        8. Realization of the possible interplanetary contamination by microbes carried in ejecta expelled by meteorites.
        9. The difficulty in conceiving of a sterile Mars in light of the new knowledge of habitability, extremophiles and the possibility of interplanetary contamination.


Comparison of Martian and Terrestrial LR Responses

The predicted Martian LR response shown in Figure 4 shows a remarkable similarity to the Martian LR response shown in Figures 11 and 15, thus fulfilling the fundamental requirement of an experiment for acceptance of the theory behind it.  Figure 6, the SN103 result of the California soil held and then tested under Martian conditions also compares favorably with the Martian results.  Figure 16 presents the response from an LR test[16] of scrapping from the interior of an endolithic Antarctic rock.  It bears a similarity to the Martian responses although showing greater gas production later in the cycle than do the Mars results.

 FIG. 16.  LR response from Endolithic Antarctic Rock Scrapings.
The responses from 0.24 g of material scraped from endolithic microorganism-populated band 10 mm beneath surface of Antarctic rock, (n−−n−−n)  active, and (−−−−) heat-sterilized control.  Experiment was performed at room temperature by LR “getter” technique and results are normalized to counting efficiency of LR flight instrument.


A number of terrestrial viable soils has shown responses quite similar in amplitude and kinetics to those from Mars.  Some are shown in Figure 17 illustrating the range of responses. 


Fig. 17.  Viking LR Response Among Terrestrial Viable Soil LR Responses.


As seen, the Viking responses are among those of lower amplitude, including responses from Barrow and Palmer, Alaska and Antarctic soil 726. 


No actual or theoretical non-biological entity meeting the constraints listed in Table 2 has yet been identified.  However, each of these constraints has been shown, as cited herein, to be met by terrestrial microorganisms of one species or another.  This includes the re-absorption of emitted gas upon second injection of nutrient, death from isolated long-term storage, and differential susceptibility to small differences in incubation temperatures. 


Challenges to Biological Interpretation

All data from VL1 and VL2 were thus either indicative or supportive of life.  However, the consensus rejected such a conclusion.  It was instead contended that the positive responses were from hydrogen peroxide theorized to be photo-chemically on Mars, or some oxidant derivative therefrom.  Hydrogen peroxide was presumed to rain from the sky and coat the surface of the planet, where it might be photo-chemically or otherwise transformed into another strong oxidant.  This oxidant was said to be responsible for destroying any organic matter and, therefore, life, thus explaining the results of the GCMS and the LR.  This theory was maintained despite the fact that the Viking Magnetic Properties experiment[17] had shown that the surface of Mars was not highly oxidized.  Were the surface material completely oxidized, it would not have been magnetic, and would not have stuck to the magnets of that experiment.  Figure 18 shows that, when the experiment’s magnets touched the surface, a heavy coat of dust stuck to the magnet.


FIG. 18.  Magnetic Properties Experiment Shows Mars Surface Not Completely Oxidized.


This demonstration that the Martian regolith was not fully oxidized was subsequently confirmed by Pathfinder as seen in Figure 19 that shows minerals in various states of oxidation.

Fig 19. Pathfinder Confirms Absence of Strong Oxidizing Coating on Mars

NASA reported[18] that Curiosity, at its location, similarly showed that the surface of Mars is not fully oxidized.  Further, “A fundamental question for this Mission is whether Mars could have supported a habitable environment,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program.  “From what we know now, the answer is yes.”

The report also says, “Scientists identified sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon – some of the key chemical ingredients for life – in the powder Curiosity drilled out of a sedimentary rock near an ancient stream bed in Gale Crater on the Red Planet last month.”  In addition, the reporting scientists discovered a mixture of oxidized, less-oxidized, and even non-oxidized chemicals capable of supporting an energy gradient of the sort many microbes on Earth require for survival:

"The range of chemical ingredients we have identified in the sample is impressive, and it suggests pairings such as sulfates and sulfides that indicate a possible chemical energy source for micro-organisms," said Paul Mahaffy, a NASA official.


The several demonstrations that Mars was not coated with a strong oxidant did not deter a series of proposals to that effect from many authors.  Over the 38 years since Viking, some 40 such chemical, physical or otherwise non-biological explanations of the LR data have been published, even as recently as this year.  Each explains away, by experiment or theory, the LR positive response.   Yet, not one of them has reproduced all the stringent control data.  This fact applies also to the finding[19],[20] of perchlorate on Mars, which the authors claim explains the failure of the Viking GCMS to detect organics.  The texts of these papers conveniently do not mention the failure to match the control data, but still claim to have reproduced the LR Mars results.  Interestingly, however, no one has challenged the performance of the LR instruments or the validity of the data they produced, or their ability to find microorganisms in terrestrial soils.  Only the interpretation of the LR data from Mars is disputed.


In addition to the strong oxidant, there were two other primary claims to a non-biological origin of the LR positive responses.  These were the continued acceptance of the lack of organic matter as reported by the Viking GCMS, and the belief in the absence of life-essential liquid water in the Martian soil. 


Organic Matter

A major difference in sensitivities could explain the seemingly disparate results of the Viking LR and GCMS.  The LR had detected as few as 20 living cells in its test program.  The Experimenter of the Viking GCMS emphasized that the instrument was not a life detector.  He pointed out that the GCMS required the organic matter contained in millions of bacterial cells to elicit a response.  Since he felt that the microbial population, if any, on Mars would be scarce, the GCMS would rely on the organic content of millions of dead cells preserved in the environment.  Thus, as the author has pointed out, both the Viking LR and GCMS could have reported correctly, there being enough living cells for the positive LR response, but too few dead and living cells for the GCMS.  In addition, as cited above, it has been proposed that organics in the Martian soil were oxidized by the perchlorates when the mixture was heated to 500o C in the GCMS analysis.  Thus, the rejection of the LR results because of the GCMS’ failure to find organic matter has been removed.


Liquid Water

The Viking LR experiment was based on the presumption that Martian microorganisms would operate on an aqueous biochemistry.  Thus, liquid water would be essential to their existence.  Viking 2 provided data establishing the presence of liquid water in the surface regolith.   As reported[21], that evidence was in the form of the temperature of the surface rising with sunlight up to 273 K, and then pausing.  This is the unique signature for ice absorbing heat without increasing its temperature while turning into liquid water.  As cited above, the Pathfinder Mission found that temperatures at the surface of Mars frequently exceeded freezing, rising into the 20 degrees C.  The Odyssey Mission orbiter found[22] hydrogen-containing material within several cm of the surface over wide areas of the red planet.  However, this and a number of additional disclosures of liquid water, including that incontrovertible data from Curiosity showing water vapor evolving when the sample was heated to just above freezing, as seen in Figure 20, were ignored along with their implication for extant life.  It is now seen that the Martian surface material contains from two to several percent liquid water.  This is considerably more than the 0.9 percent found in the top sands of Death Valley that supports a thriving microbial ecology that was readily detected by the LR.   Curiosity data have led to the NASA statement that its principal mission objective has been accomplished: finding that the past environment of Mars was habitable.  However, no mention regarding current habitability was made.


FIG. 20.  Curiosity Data Show Liquid Water in Mars Surface Material.


The Evidence in Summary

Evidence that the LR detected life on Mars consists of the following elements:


This evidence is supported by:


The above summation indicates that Carl Sagan’s challenge, “Extraordinary claims require extraordinary evidence,” as often applied to the Viking LR, has now been met.  The extraordinary claims have become ordinary, and the evidence has become extraordinary.


Baye’s Rule

Were an objectivist’s view of Baye’s Rule of Inference[23] applied to the increasing knowledge about Mars since Viking, the probability that the LR detected life would be significantly increased.  Assigning weighting factors to each of these new bits of information for a rigorous application of Baye’s Rule is difficult and would obviously be inexact.   Similarly, assessments would have to be assigned for each of the non-biological explanations.  However, allowing only a very small probability for the existence of life on Mars at the time of Viking, 1976, the supportive findings since, together with the difficulties with the non-biological attempts to explain away the LR data, are such as to instill a significant rise in the Baye’s Rule’s present confidence that the LR detected life.  The fact that nothing antithetical to life on Mars has been discovered by all the post-Viking research has significant impact on the present probability.  


NASA Turning Point

In 2012, following publication[24] of a new and independent approach to analysis of the Viking LR data that indicated it had obtained a biological response, NASA’s Director of the Mars Exploration Program was quoted[25] as saying NASA would now seek direct life detection experiments, including the use of Curiosity’s hi-resolution camera that can resolve features as tiny as 12.5 microns to seek possible growths on rocks originally reported[26] with colored patches in Viking images. 


Curiosity and Life on Mars

The rover of the Mars Science Laboratory, “Curiosity,” has now been on the surface of Mars for nearly two years.  When NASA announced that the mission carried no life detection experiment or capability, the senior author laid claim[27] to Curiosity’s abilities to confirm the detection of life by the Viking LR.  Specifically, the referenced paper predicted: 1. that Curiosity would find liquid water in the surface material of Mars, confirming Viking’s original discovery, and 2. that Curiosity’s liquid extraction method of detecting organic matter would find complex organics in the soil.  In addition, the paper projected that the Hand Lens camera might detect biological features in close-up examination of the greenish colored spots seen on many rocks in images transmitted by Curiosity, similar to those seen[28] in images of Viking site rocks. 


The prediction of finding liquid water has materialized as seen in Figure 20.  No results of the liquid extraction of organic matter have been reported, nor have any close-up images of the rocks been shown.  Repeated requests to NASA for Curiosity data on liquid water, complex organics and hi-resolution, close-up images of rocks, including a request[29] under the Freedom of Information Act (FOIA), have been answered with denials that the data exist.  It is contended that the liquid extraction method for organics has not yet been run, that all images taken by Curiosity have been published.  It seems strange that eager scientists would hazard a two-year wait before executing important experiments.  Viking performed its critical experiments as soon as possible for fear of losing communication with the spacecraft or of some accident or malfunction to systems exposed to such a hostile environment.  Nonetheless, the prediction for Curiosity’s finding complex organics in support of the Viking LR conclusion remains, as does the expectation for possible biological evidence in hi-resolution images.



This paper attempts to show, in simple narrative fashion, how the Viking LR experiment was planned and executed in strict conformance with classic scientific principles guiding exploration and discovery.  The hypothesis was formulated that microorganisms existed on Mars operating under an aqueous biochemistry similar to that on Earth.  An experiment was conceived to test the hypothesis.  The experiment was performed.  It produced positive results.  The experiment was successfully duplicated.  The entire experiment was then replicated at a site 4,000 miles distant.  It was again positive.  Its duplication was also positive.  A variety of ad hoc experiments further supported, or were consistent with, a biological interpretation of the Viking LR data. 


The first Viking LR experiment and control satisfied the pre-mission criteria accepted by NASA and participating scientists for the detection of life.  Had it been performed on Earth, this experiment would readily have been accepted as having detected life.  The remainder of the planned LR experiments and the ad hoc experiments on Mars supported or were consistent with the conclusion that microbial life had been detected.  However, largely because of the failure of the Viking GCMS to detect any organic matter, the biological origin of the LR positive signals was not generally accepted.  This was despite the large discrepancy in the sensitivities of the two instruments that could readily explain the different interpretations of their results.  Many other barriers to a biological explanation have since been raised.  A wide variety of non-biological explanations of the Viking LR results have been proposed, but none has duplicated the test and control data generated by the LR on Mars.  When pressed for reasons for having rejected the biological interpretation of the Viking LR results, NASA and other scientists have said that the consensus was against such a conclusion.  This ignores the fact that no important discovery was met with a consensus.  If so, it would not have been a discovery.  Many key discoveries have taken scores of years before wide acceptance.  The authors believe that such a price has now been paid for acceptance of life on Mars, and ask for reconsideration in the light of the support that has emerged since Viking. 


Beginning with Viking and increasingly over the years since, some scientists knowledgeable in the field have expressed their opinions on the LR Martian results to the senior author directly or in public statements.  Thinking that other scientists might be swayed in their opinions by knowing how these experts have evaluated the Viking LR data, we have prepared a list of those respondents.  Depending on what they had said, the scientists were listed in the category of “Has Detected Life,” or “May Have Detected Life.”  That list was then emailed to those named in it, and permission to include his or her name was requested.  The updated list, with each name newly approved for use in this paper, is shown in Table 3.  



TABLE 3.  Scientists Stating the Viking LR Detected or May Have Detected Life.


Life on Mars Was Detected by the Viking LR Experiment




Giorgio Biancardi                

Siena U., Siena, Italy      

Francisco Carrapico            

U. Lisbon, Lisbon, Portugal

Mario Crocco                       

Ministry of Health, Argentine Republic, Buenos Aries, Argentina

Barry DiGregorio     

U. Buckingham (UK)

Richard B. Hoover           

U. Texas, Athens, (NASA ret.)

Joop M. Houtkooper

Justis-Liebig U., Giessen, DE

Gilbert Levin

Arizona State U., LR Experimenter


Ron Levin


Robert Lodder

U. Kentucky

Joseph Miller                  

Am. U. Caribbean, Sch. Med. 

John Newcomb

NASA, Viking Manager (ret.)

Elena Pikuta                   

Athens State U., Texas      

Dirk Schulze-Makuch    

Washington State U.         

Patricia A. Straat          

NIH (ret.), LR Co-Experimenter

Hans Van Dongen

Washington State U, Spokane

Chandra Wickramasinghe

U. Buckingham, UK   

Life on Mars May Have Been Detected by the Viking LR Experiment




Ariel Anbar                   

Arizona State U.                   

Timothy Barker           

Wheaton College                   

Steven Benner              

U. Florida                               

Paul Davies                   

Arizona State U.                    

Sergio Fonti                  

U. Salento, Italy                     

Robert Hazen              

Carnegie Institution, DC            

Bruce Jakosky            

U. Colorado                

Chris McKay               

NASA Ames                             

Richard Meserve         

Carnegie Institution, DC        

Michael Mumma        

Goddard Space Flight Center

Vincenzo Orofino       

U. Salento, Italy                 

John Rummel             

East Carolina U. (ex NASA)

Andrew Steele            

Carnegie Institution, DC   

Carol Stoker               

NASA Ames                       

Mike Storrie-Lombardi  

Kinohi Inst., Pasadena, CA 

Henry Sun                   

Desert Research Inst., Reno



A classic, rigorous test has been made of the hypothesis that Mars is inhabited by microorganisms similar in their biochemistry to terrestrial life.  Duplicates and replicates of the LR experiment to investigate that theory have given strong or supportive evidence for life on the red planet, with no incompatibilities with life found.  The pre-mission criteria for the detection life have been exceeded.  The authors believe the evidence cited herein establishes the existence of life on Mars.  The absence of any tenable non-biological challenge emphasizes this claim, but is not relied upon, Sherlock Holmes-like[30], as the basis of this conclusion: “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.”  Further to the point, since Viking, research into interplanetary microbial contamination has made it extremely unlikely that Mars could be sterile.  All signs now point to another major change in our ancient anthropocentricity.  We are not alone.  A way to initiate this historic change would be for all the evidence, pro and con, on the LR experiment and related issues bearing on the question of life on Mars to be examined.  The evidence would be submitted to a panel of experts assembled by a major intellectual institution.  The panel should make a formal report on whether or not the evidence proves the existence of microbial life on Mars.  A positive answer would start the needed change in paradigm, and spur further life detection experimentation.  However, even a negative answer would be very valuable.  It would undoubtedly provide information that would influence NASA’s planetary program, increasing its scientific return and providing significant economic savings. 



In the event the expert panel does not resolve the issue of life on Mars, it is proposed that the next mission there carry the Chiral LR experiment[31].  A schematic of the current concept for that instrument is shown if Figure 21.



FIG. 21.  Schematic of the Chiral LR Instrument.


This enhancement of the Viking LR would separately test for the chiral metabolism of stereoisomer compounds selected as nutrients.  All known life forms react only with L-amino acids and D-carbohydrates.  Chemicals cannot distinguish between stereoisomers.  The experiment could be deployed as multiple darts ejected from a landed spacecraft or from orbit.  Each small dart could contain different isomeric compounds for testing.  Duplicate darts could be included for verification and redundancy against the loss of one.  A variety of controls, thermal, chemical and physical, could be incorporated to support or deny any positive findings.  If only one of the isomers of a compound produced an LR response, and it was confirmed by a control, this would be strong evidence for life.  Were the isomeric preference found to be similar to that on Earth, that would suggest the two forms of life are related, perhaps by cross-infection, or by seeding from a third source.  However, if the response were to D-amino acids or to L-carbohydrates, it would constitute strong evidence for an independent genesis of Martian life.  Either way, the discovery would mark the beginning of interplanetary comparative biology.  Should Mars and Earth show independent origins of life, this sample, small as it is, could be viewed as statistical evidence for life having originated or having been distributed throughout the cosmos.     



Thanks are given to Dr. Paul Davies who kindly reviewed this work and made several important suggestions, including reference to Baye’s Rule.


Dr. Ron Levin is thanked for his scientific support on the issue of liquid water on Mars, and for his encouragement on the life issue itself, as well as for his preparation of the PowerPoint figures in this presentation.





[1]   Onofri, S., et al., “Survival of Rock-Colonizing Organisms after 1.5 Years in Outer Space,” Astrobiology, 12, 5, 2012.

[2]   Horneck, G., et al., “Resistance of Bacterial Endospores to Outer Space,” Astrobiology, 12, 5, 2012.

[3]   Vaishampayan, P. A., et al., “Survival of Bacillus pumilus Spores for a Prolonged Period of Time in Real Space Conditions,” Astrobiology, 12, 5, 2012.

[4]   Carpenter, E.J., S. Lin, and D.G. Capone, “Bacterial Activity in South Pole Snow,” Applied and Environmental Microbiology 66, 10, 4514-4517, 2000.

[5]   Grotzinger, J. P., et al., “A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars,” Science, 343, 6169, 2014.

[6], “Weather on Mars Surprisingly Warm, Curiosity Rover Finds” Staff, October 1, 2012.

[7]   Schofield, J.T. et al., “The Mars Pathfinder Atmospheric Structure Investigation/Meteorology (ASI/MET) Experiment,” Science 28, 1752-1758, 1997.

[8]   NASA, “PDS Geoscience Node: IRTM Version 2,” http://pds-, 1994.

[9]   Ming, D.W., et al., “Volatile and Organic Compositions of Sedimentary Rocks in Yellowknife Bay, Gale Crater, Mars,” Science, 343, 6169, 2014.

[10]  Levin, G.V., “Scientific Logic for Life on Mars,” Instruments, Methods, and Missions for Astrobiology, SPIE Proc., 4495, 81-88, 2001.

[11]  Davies, P., “The transfer of viable micro-organisms between planets,” in G. Brock and J. Goode. (Ed.), Evolution of Hydrothermal Ecosystems on Earth (and Mars?): Proc., CIBA Foundation Symposium, No. 20, New York, Wiley, p. 304, 1996.

[12]  Mileikowsky, C. et al., “Natural Transfer of Viable Microbes in Space 1. From Mars to Earth and Earth to Mars,” Icarus 146, 2, 391-427, 2000.

[13]  Standard Methods for the Examination of Water and Wastewater, Am. Pub. Health Assn., Am. Water Works Assn., Water Environment Fed., NY, 2005.

[14]  Levin, G. V., et al., “Rapid Bacteriological Detection and Identification,” Second United Nations International Conference on the Peaceful Uses of Atomic Energy, A/Conf. 15/P/820, USA, June 1958. 

[15]  Levin, G. V., “Detection of Metabolically Produced Labeled Gas: the Viking Mars Lander,” Icarus, 16, 153-166, 1972.

[16] Levin, G. V. and P. A. Straat, “Antarctic Soil No. 726 and Implications for the

    Viking Labeled Release Experiment,” J. Theor. Biol., 91, 41-45, 1981.

[17]  Hargraves, R.B., et al., “The Viking Magnetic Properties Experiment: Primary Mission Results,” J. Geophys. Res., 82, 4547, 1977.

[18]  NASA, “3 Things Curiosity Found About Mars that Make the Red Planet Habitable,” reported by Tom McKay in online Policy Mic, Mar. 12, 2013.

[19]  Navarro-González et al., “The limitations on organic detection in Mars-like soils by thermal volatilization–gas chromatography–MS and their implications for the Viking results,” 2006.

[20]  Benner, S. A., et al., “The Missing Organic Molecules on Mars,” 6, 2425-2430, PNAS, 2,000.

[21]  Moore, H.J. et al., "Surface Materials of the Viking Landing Sites," J. Geophys. Res., 82:28, 4497-4523, 1977.

[22]  Levin, G. V., “Odyssey Gives Evidence for Liquid Water on Mars,” Instruments, Methods, and Missions for Astrobiology, SPIE Proc. , 5163, 16, 2003.

[23]  Jeffrey’s, H., Scientific Inference, 3rd ed., Cambridge U. Press, p. 31,
ISBN 978-0-521-18078-8, 1973.

[24]  Bianciardi, G., et al., “Complexity Analysis of the Viking Labeled Release Experiments,” Int'l J. of Aeronautical & Space Sci. 13(1), 14-26, 2012.

[25]  Covault, C., “Life on Mars An Historic Reality, NASA Gears for New Emphasis,” Exploration, JPL, Mars, NASA, Apr. 16, 2012.

[26]  Levin, G. V., et al., “Color and Feature Changes at Mars Viking Lander Site,” J. Theoretical Biol., 75, 381-390, 1978.

[27]  Levin, G. V.,“Stealth Life Detection Instruments Aboard Curiosity,” Instruments, Methods, and Missions for Astrobiology XV, SPIE Proc., 8521, 852102-1, 2012.

[28]  Op. Cit. 26.

[29]  FOIA, see <>, tab “Mars Research.”

[30]  Doyle, Arthur Conan.  The Sign of Four, Spencer Blackett, London, Chapt. 6, P. 111, 1890.

[31]  Levin, G. V., “The Search for Life on Mars – and Earth: a Call for Objectivity and a New Proposal,” J. of Cosmology, 16, 2011.

RESEARCH ON MARS – Papers by Gilbert V. Levin, Ph.D.

In 1952, Dr. Gilbert V. Levin invented a rapid, highly sensitive method to detect microbial contamination of water and food. In 1958, he obtained a NASA contract to develop the method to seek extraterrestrial life. The method was selected in 1969 for use on NASA’s 1976 Viking Mission to Mars. Originally named “Gulliver,” for the Lilliputians (microorganisms) it was seeking, it was renamed the “Labeled Release (LR)” experiment by NASA to indicate the technology used – the release of radioactive gas from radio-labeled compounds in the event they were metabolized by microorganisms in the Martian soil. Simply put, the LR squirted a drop of carefully designed radioactive food onto a tiny cup of Martian soil and monitored the air above the soil to detect radioactive gas that any microorganisms present might breathe out. Levin and his co-workers, notably Dr. Patricia Ann Straat, then spent the next decade developing the experiment and instrument, and in analyzing the results obtained from its successful operation on Mars. At both landing sites, some 4,000 miles apart, the LR returned evidence of living microorganisms. Initially discounted by NASA and most space scientists, the results of this milestone project have, nonetheless, been causing excitement and controversy ever since. In 1997, after 21 years of study of the Mars LR results, of new information scientists obtained about environmental conditions on Mars, and of the extreme environments in which life was found on Earth, Dr. Levin published his conclusion that the LR had, indeed, discovered living microorganisms on the Red Planet.

Levin first presented his conclusion in an invited talk at the Annual Meeting of the International Society for Optical Engineering (SPIE) on July 30, 1997, in San Diego. On July 20, 1998, he presented another paper with new findings supporting that conclusion. Many attempts have been made since then by other authors to explain the Mars LR results as having been caused by chemical or physical reactions between the LR nutrients and the soil. No one, however, has duplicated the full experimental results the LR obtained on Mars. In recent years, there have been many important converts to the life theory, possibly the fore-runner of a major paradigm shift in humanity’s continual search for its place in the universe.

Below are his publications related to Mars. They are presented in chronological order, from the early up to the latest scientific findings by him and others related to this intriguing issue, the resolution of which, as termed by NASA, would be “the greatest experiment in the history of science.”


**some of these documents may take several minutes to fully load due to graphics and long text

·     Mars Life: Been There, Done That?,
Alan Boyle, MSNBC,
Mar. 27, 2012


·     The Viking Mission and Life on Mars,
G. V. Levin, with A. I. Oparin, et al., Life Origin and Evolution (in Portuguese), eds. Levy, A., Carrapico, F., Abreu, H and Pina, M., Esfero Do Caos Editores LDA, Lisbon, Portugal, 2011.

·     Ramifications of a Sterile Mars,
G. V. Levin, Instruments, Methods and Missions for Astrobiology, XIV, SPIE Proceedings, eds. RB Hoover, GV Levin; AY Rozanov and Paul Davies, Paper 8152-11, 2011.

·     The Search for Life on Mars – and Earth: a Call for Objectivity,
G. V. Levin, Journal of Cosmology, Vol.16, 2011.

·     The Goldilocks Problem for Life: Its Possible Solution,
G. V. Levin, Life in the Cosmos Panel Discussion, Panel Moderators: Richard B. Hoover, NASA Marshall Space Flight Ctr.; Paul Davies, Arizona State Univ.; Alexei Yu. Rozanov, Paleontological Institute (Russian), Instruments, Methods and Missions for Astrobiology, XIV, San Diego, CA, August 23, 2011.

·     Mars: The Living Planet, Chapter 9 Revisited,
G. V. Levin, in The Microbes of Mars – a 2011 Addendum to Mars: The Living Planet, Barry DiGregorio, - Kindle Edition - Kindle eBook, 2011.

·     Review of the book “We Are Not Alone: Why We Have Already Found Extraterrestrial Life”, by Dirk Schulze-Makuch and David Darling.  reviewed by G. V. Levin, EARTH Vol. 55 (No. 11), p. 67, Nov., 2010.

·     It's Time to Realize there is Life on Mars,
G. V. Levin, Earth, 86, Oct., 2010.

·     Solving the Problems with Chirality as a Biomarker for Alien Life,
G. V. Levin, Instruments, Methods and Missions for Astrobiology, eds. RB Hoover, GV Levin; AY Rozanov and Paul Davies, SPIE Proceedings, 7819, 14, 2010.

·     The Likelihood of Methane-producing Microbes on Mars,
Miller, J. D., M. J. Case, and G. V. Levin,
Instruments, Methods, and Missions for Astrobiology XIII, SPIE Proc., 7819, 15, 2010.

·     Can Chirality Give Proof of Extinct or Extant Life?,
G. V. Levin, Astrobiology Science Conference 2010, April 26–29, 2010

·     Extant Life on Mars: Resolving the Issues,
G. V. Levin, J. of Cosmology, 5, 920-929, 2010.

·     Methane and Life on Mars
G. V. Levin and P. A. Straat, Instruments, Methods and Missions for Astrobiology and Planetary Missions XII, RB Hoover, GV Levin, AY Rozanov, and KD Retherford, eds., SPIE Proceedings, vol. 7441, invited paper, no. 744110D, Aug. 5, 2009.

·     Stereo-Specific Glucose Consumption May Be Used to Distinguish Between Chemical and Biological Reactivity on Mars: A Preliminary Test on Earth, comment,
G. V. Levin, ASTROBIOLOGY, Volume 9, Number 5, 2009 (w response)

·     The Revival Of Life On Mars,
G. V. Levin, Instruments, Methods and Missions for Astrobiology X, eds. RB Hoover, GV Levin, AY Rozanov, and
PCW Davies, SPIE Proceedings, 6694, paper number 6694-21, August 29, 2007.

·     Analysis of evidence of Mars life,
G. V. Levin, The Carnegie Institution Geological Laboratory Seminar, May 14, 2007.

·     Possible Evidence for Panspermia: the Labeled Release Experiment,
G. V. Levin, International Journal of Astrobiology, 6, 2, 95-108, 2007.

·     Detecting Life and Biology-Related Parameters on Mars,
GV Levin, JD Miller, PA Straat, RA Lodder, RB Hoover, IEEE Aerospace Conference, vol. 1, 2007.

·     Modern myths of Mars,
Instruments, Methods and Missions for Astrobiology, eds. RB Hoover, GV Levin and AY Rozanov, SPIE Proceedings, 6309, 6309OC-1 – 6309OC-15, September 1, 2006.

·     Mars life - how Darwinian pressures might have shaped its form and function, Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, 5906, OD1-10, August 2005.

·     A circadian biosignature in the Labeled Release data from Mars?
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, 5906, OC1-10, August 2005.

·     News out of ESA Mars Conference in the Netherlands,
75 percent of the attending scientists now believe that Mars may have had life.

·     Interpretation of new results from Mars with respect to life,
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings 5555, 14, August 2004.

·     Color Calibration of the Martian images,
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings 5555, 29, August 2004.

·     Color Calibration of Spirit and Opportunity Rover Images,
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings 5555, 30, August 2004.

·     Water Everywhere,
Space News International, January 19, 2004.

·     Finding Life on Mars Would Not Surprise One Scientist,
Newhouse News Service, January 16, 2004.

·     Solving the color calibration problem of Martian lander images,
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings 5163, 19, August 2003.

·     Odyssey gives evidence for liquid water on Mars,
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings 5163, 16, August 2003.

·     Iron(VI) Seems an Unlikely Explanation for Viking Labeled Release Results,
Icarus 159, 1, 266-267, September 1, 2002 (and the rebuttal of Tsapin et al.).

·     A Sterile Robotic Mars Soil Analyzer, Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, 4859, 78-86, August 2002.

·     NASA-sponsored Washington University at St. Louis website
on Spherix' Viking Labeled Release life detection experiment on Mars.

·     Life on Mars, Dawn of a New Age,
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, poster presentation, July 2001.

·     Scientific Logic for Life on Mars,
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, 4495, 81-88, July 2001.

·     The Oxides of Mars,
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, 4495, 131-135, July 2001.

·     Periodic Analysis of the Viking Lander Labeled Release Experiment,
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, 4495, 96-107, July 2001.

·     Approaches to Resolving the Question of Life on Mars
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, 4137, 48-62, August 2000.

·     An Unambiguous Martian Life Detection Experiment,
Poster Presentation at The Future Search for Life on Mars, Lunar And Planetary Institute, Houston, TX, November 2-4, 1998.

·     Liquid water and life on Mars,
Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, 3441, 30-41, July 1998. 

·     The Mars Oxidant Experiment (MOx) for Mars,
Planetary and Space Science, Vol 46, Iss 6-7, pp 769-777, June-July 1998.

·     The Viking Labeled Release Experiment and Life on Mars,
Instruments, Methods, and Missions for the Investigation of Extraterrestrial Microorganisms, SPIE Proceedings, 3111, 146-161, July 1997.

·     Life After Viking: The Evidence Mounts,
287-311 in DiGregorio, B., Mars, the Living Planet, Frog, Ltd.
c/o North Atlantic Books, Berkeley (1997).

·     Investigating the Surface Chemistry of Mars,
Analytical Chemistry, October, 1995.

·     The Oxidant on Mars - Chemistry or Biology?,
International Tesla Society Mars Forum, Colorado Springs, CO, November 13, 1993.

·     Book Review of MARS, Kieffer, H. et al.,
University of Arizona Press, Tucson and London, 1992, In IEEE Spectrum, November 1993.

·     Book Review of Mars Beckons,
Wilford, John Noble, Alfred A. Knopf, New York, 1990, In Spectrum, 27, 11, December, 1990.

·     A Reappraisal of Life on Mars.,
The NASA Mars Conference, Science and Technology Series, 71, 186-210, 1988.

·     The Life on Mars Dilemma and the Sample Return Mission,
Proc. Mars Sample Return Science Workshop, Houston, 1987.

·     Antarctic Soil No. 726 and Implications For the Viking Labeled Release Experiment,
Je. Theor. Biol., 91, 41-45 (1981).

·     A Search for a Nonbiological Explanation of the Viking Labeled Release Life Detection Experiment,
Icarus 45, 494-516 (1981).

·     Completion of the Viking Labeled Release Experiment on Mars,
Journal of Molecular Evolution, 14, 167-183, 1979.

·     Laboratory Simulations of the Viking Labeled Release Experiment:
Kinetics Following Second Nutrient Injection and the Nature of the Gaseous End Product
J. Mol. Evol., 14, 185-197 (1979).

·     Viking Mars Labeled Release Results,
Nature, 277, 327, (1979).

·     Color and Feature Changes at Mars Viking Lander Site,
Journal of Theoretical Biology, (1978) 75, 381-390.

·     The Labeled Release Experiment - New Laboratory and Mars Data,
(COSPAR), Abstract, XXIst Plenary Meeting, Innsbruck, (1978).

·     Biology or Chemistry? The Viking Labeled Release Experiment on Mars,
Abstract, XXth Plenary Meeting of COSPAR, Tel Aviv, (1977).

·     The Viking Labeled Release Experiment: Current Status of Flight Data and Laboratory Simulations,
Abstracts of the Annual Meeting, American Society for Microbiology, 95, (1977).

·     Recent Results From the Viking Labeled Release Experiment on Mars,
Journal of Geophysical Research, Vol. 82, No. 28; September 30, 1977.

·     Life on Mars? The Viking Labeled Release Experiment,
Biosystems, 9(1977) 165-174.

·     Labeled Release - An Experiment in Radiorespirometry,
Origins of Life 7(1976) 293-311.

·     Water on Mars and the Viking Biology Experiment,
Proc. Colloquium on Water in Planetary Regoliths,
Dartmouth College, October 1976.

·     Viking Labeled Release Biology Experiment: Interim Results,
Science, 194, 1322-1329, (1976).

·     The Viking Biological Investigation: Preliminary Results
Science, 194, 4260, 99-105 (1976).

·     The Viking Mission Search for Life on Mars,
Nature, 262, 5563, 24-27 (1976).

·     Mariner 9: Prelude to First Field Test of a General Theory of Biology?,
Publication No. X-922-74-310, Goddard Space Flight Center, NASA, Greenbelt, MD, November 1974.

·     Detection of Metabolically Produced Labeled Gas: The Viking Mars Lander,
Icarus, 16, 153-166, 1972.

·     Infrared Spectroscopy Experiment on the Mariner 9 Mission: Preliminary Results,
Science, 175, 305-308, January 1972.

·     Investigation of the Martian Environment by Infrared Spectroscopy on Mariner 9,
Icarus, 17, 423-442, 1972.

·     Infrared Spectroscopy Experiment for Mariner Mars 1971,
Icarus, 12, 48-62, 1970.

·     Experiments and Instrumentation for Extraterrestrial Life Detection,
Advances in Applied Microbiology, 10, 55-71, Academic Press, New York, 1968.

·     Life Detection by Means of Metabolic Experiments,
The Search for Extraterrestrial Life, 22, Advances in the Astronautical Sciences Series, 223-251, Am. Astro. Soc., 1967.

·     Extraterrestrial Life Detection with Isotopes and Some Aerospace Applications,
Radioisotopes for Aerospace, Part 2: Systems and Applications, 347-357, Plenum Press, New York, 1966.

·     Significance and Status of Exobiology,
BioScience, 15, 1, 17-20, 1965.

·     Gulliver and Diogenes-Exobiological Antitheses,
COSPAR, Life Sciences and Space Research III, 105-119, North-Holland Publishing Co., Amsterdam, 1965.

·     Biological Objectives of Unmanned Exploration of the Solar System,
Advances in the Astronautical Sciences, 19 American Astronautical Society, 1965.

·     Mark IV Gulliver-An In Situ Instrument for Extraterrestrial Life Detection,
Digest of the 6th International Conference on Medical Electronics and Biological Engineering, Tokyo, 324-325, 1965.

·     The Interplanetary Olympics Begin
(editorial), BioScience, 15, 1, 15, January 1965.

·     Panel Discussion, Biological Objectives of Unmanned Exploration of the Solar System,
Proceedings of the American Astronomical Society Symposium on Unmanned Exploration of the Solar System, Denver, Colorado, February 8-10, 1965.

·     ‘Gulliver’-An Experiment for Extraterrestrial Life Detection and Analysis Life Sciences and Space Research II, 6, 124-132, North-Holland Publishing Co., Amsterdam, 1964.

·     ‘Gulliver’-A Quest for Life on Mars,
Science, 138, 3537, 114-121, October 12, 1962.

·     Life on Mars?,
Nucleonics, 20, 10, 71-72, October 1962.

·     Detection of Microorganisms on Other Planets,
American Nuclear Society Transactions, 5, 2, 279, November 1962.

Back To Top»





1.          At Viking 2, The temperatures of the soil in contact with the soil collector head, measured by a thermocouple, rose as the Sun rose to, and a little beyond, the zenith. The temperature of the soil beneath the collector head at the Viking 2 site reached 273 degrees Kelvin (0 degrees Centigrade, the melting point of water ice), at 14.21 (2:21 p.m.) local lander time, on Sol 41, and did not rise above that during the “10-minute or more” measuring interval (Moore, H.J. et al., "Surface Materials of the Viking Landing Sites," J. Geophys. Res., 82:28, 4497-4523, 1977.)  

Nothing else behaves this way but ice melting to liquid. Furthermore, because the melting point of the ice was 273K, this is proof that the water ice was virtually pure water, not brine as suggested by many, nor even salty.  Had salt been present, the melting point would have been lower than 273K (still in a range monitored by Viking).  The melting point of a compound is definite proof of its identity, just as a fingerprint or DNA.  

2.          Carr (Carr, M. H., Water on Mars, Figure 1-2, P 10, Oxford University Press, New York, 1996.) states, “Water vapor was assumed to be distributed throughout the entire atmospheric column.” The Mars Atmospheric Water Detector (MAWD) determined 10 to 100 um of precipitable water vapor in the Mars atmospheric column.  However, as determined by Pathfinder, the warm part of the atmosphere is confined to less than one meter, perhaps only centimeters, above the surface. Thus, the saturation of the atmosphere reported by MAWD must be near the surface.  If so, it must be in equilibrium with the surface material where that equilibrium would include water in liquid phase.

3.          Carr, cited above, points out that “As long as the total atmospheric pressure exceeds the triple point, liquid water will not boil, and, if formed, could exist on the surface for a biologically significant time.”

Here is the triple point diagram of water, showing temperatures and atmospheric pressure for water as solid, liquid and gas.  The ranges on Mars where measured temperatures and pressures require water be in liquid phase are hatched in red (Levin, G. V. and R. Levin, “Liquid water and life on Mars,” Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, 3441, 30-41, July 1998). 


4.          This NASA image shows ice as snow or frost at the site of Viking 2.




5.   Experiments done at UC Berkeley simulating Martian environmental conditions showed water ice to liquefy and remain for biologically significant periods of time (Levin, G. V., Life on Mars, Dawn of a New Age, Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings, poster presentation, July 2001).

  1. 6.     Odyssey findings: “CO2 Snow Depth and Subsurface Water-Ice Abundance in the Northern Hemisphere of Mars,” G. Mitrofanov et al. Science, 300, 2081-2084, 2003; Los Alamos National Laboratory, News Release, July 24, 2003.) reported this year reveal the Mars north polar area to be even richer in hydrogen and of greater extent, including towards equatorial latitudes, than in the south polar and adjacent regions.  The July 24 news release confirms and extends these findings, reporting up to 50 percent water by mass in polar regions and from two to ten percent in areas closer to the equator.
    1. The Pathfinder surface atmospheric pressure and thermal data show that the conditions for liquid



     water prevail on Mars.

8.  Levin, G. V., “If it looks like muck, and it puddles like muck, and it. tracks like muck, it must be muck.” In “ Interpretation of new results from Mars with respect to life,” Instruments, Methods, and Missions for Astrobiology, SPIE Proceedings 5555, 14, 2004.

NASA image:

                    Image from Rover Opportunity, showing tracks made by collapsing air bag dragged through what appears to be mud.


9.  Phoenix photographed droplets of water on lander strut.

Droplets (highlighted in green) appear to merge in a series of shots taken from the Phoenix Mars Lander

10.  Finally, as Groucho said, “Who do you believe, me or your own eyes?”