Viking Results Mars
Gabor Kiss
Viking Lander Mission schedule
Spacecraft & Instruments
The Gas Chromatograph Mass Spectrometer
Gas Exchange Experiment
Labeled Release Experiment
Pyrolytic Release Experiment
Reanalysis & Landing
References
Viking Lander Mission schedule
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2
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Start:
August 20, 1975
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Start:
September 9, 1975
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Ankunft:
June 19, 1976
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Ankunft:
August 7, 1976
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Landung:
July 20, 1976
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Landung:
September 3, 1976
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Ort: Chryse Planitia
(22.48° N, 49.97° W)
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Ort: Utopia Planitia
(47.97° N, 225.74° W)
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Last Contact:
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Last Contact:
November 13, 1982
April 11, 1980
Spacecraft & Instruments
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Bioshield - prevent contamination
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2 radioisotope thermal generator (RTG) units (plutonium 238)
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4 x 28 volt rechargeable batteries
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Propulsion - Deorbit monopropellant
hydrazine (N2H4) rocket
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Landing: 3 Monopropellant hydrazine
engines (120°) 18 nozzles (276 -2667N)
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Hydrazine purified; 85 kg
Viking Lander
Primary scientific objectives:
 Biology
 Seismology
 Chemical composition (organic and
inorganic)
 Magnetic properties
 Meteorology
 Physical properties of martian surface
and atmosphere
• 2 x 360-degree cylindrical scan cameras
• sampler arm, collector head, temperature sensor and magnet on the end.
• meteorology boom, wind direction, wind velocity sensors
• seismometer, magnet & camera test targets, magnifying mirror
• biology experiment & gas chromatograph mass spectrometer.
• X-ray flourescence spectrometer
• pressure sensor
The Biological Load - GCMS
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Mass: 15.0 kg
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Search Martian organisms by metabolic
products
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Gas Chromatograph – Mass
spectrometer
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Mass: 19.0 kg
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Meassuring ppb
GCMS
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1) sample crushed and heated up in oven
625°C -> Gas transferred with H2
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2) Gas from soil sample and carrier gas
stream through GC filtersystem
1
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3) filtered Gas in seperator, pressure
regulation, seperator of Palladium-alloy, leads
to discharge of hydrogen
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4) Mass-Spectrometer: Gas molecules in high
–voltage field leads to ionization, magnetic
lense focusing to a small beam
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5) Ionized Gas pass Magnetic field, chemical
components aligned according to their
molecular weight
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6) Electron-multiplier, chemical analysis
transformed into electrical signs
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2
3
4
5
Gas Exchange Experiment
Humid Mode
– Humid Nonnutrient mode: Martians are waiting dorment in
the dry martian soil until enough moisture -> stimulating
metabolism -> Atmosphere analysed by GC
Sol (24h 39min 35,244 sec syn.) is limiting factor for growth of
martian organism
Simple nutrient with organic compounds
– Sample and martian atmosphere incubated with added CO2
and Krypton and Helium, total pressure 200mbar; 0.5cc
nutrient added, but no contact with sample, rapid saturation
of atmosphere with water, incubation temperatur between 815°C, test: 7 days
– Test once by each Lander
Gas Exchange Experiment
Wet Nutrient Mode
• Significant fraction of Martian biota is heterotrophic
• Addition of organic compounds necessary for metabolic
response (only in aqueous environment)
• Large number of different organic and inorganic compounds
• Experiment 3 times:
– 200sol VL1
– 31 sol VL2
– 116 sol VL2
inkubation 13 sols
inkubation 19 sols
inkubation 78 sols
Atomsphere: CO2, Krypton, Helium, 200mbar, Temperatures 8-15°C
GEx
VL1, Chryse Sandy Flats sample; Oyama and Berdahl: Gex Viking Results
GEx Results
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Humid mode:
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CO2 and N2 desorbed from soil, rapid
accumulation of oxygen
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Release of oxygen never seen before
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Poorly understood and very rapid (2 ½ hour)
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later addition of water no more reaction,
further in dark, so no biological explanation
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Wet mode:
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after contact, 30% of CO2 went into solution
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CO2 slowly continually produced, returned to original
level and increased with time
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No other gas changes of biological origin
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Absorption of CO2 also in sterilizied samples
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After nutrient drained out and fresh added,
production rate of CO2slowed down each time
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Reactions also seen in sterile terrestrial samples
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Uptake of CO2 from Metal oxides, hydroxides,
created by interaction of water with peroxides,
superoxides
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γ-Fe2O3 nutrient oxidizing by secondary oxidant, like
iron oxide
Same reaction in preheated „sterilized“
sample
Hydrogenperoxide unlikely, because not
survived heating
Gex Results
– Results: just physical and chemical reactions:
desorption of gases and generation of oxygen
– Biology: negative!
– Wrong assumptions:
• no source of energy (dark)
• incubation temperatur to high?
• 7 days of incubation to short? Antarctic samples needed
months!
• High atmospheric pressure
Labeled Release Experiment
• Assumption: heterotrophic organisms on Mars, capable of decomposing
one or more simple organic compounds labeled with radioactive 14C
– Not heat sterilized: 4 inkubations of 13, 52 and 90 days at 10°C, addition of small
volume water dilute solution of organic subtrates
– Incubation cell pressurized 60 mbar
– Heat sterilized: 3 samples with 160°C, 50°C and 44°C
– Results: not sterilized samples -> decomposing nutrient!
– 95% of labeled 14C stayed in sample
– Prior heating terminated reaction after 3 hours
– All tested samples yielded oxygen -> superoxide, oxidant
– At least 2 oxidizeres or reaction of nutrient with martian soil?
Labeled Release
3rd sample of VL2; Radioactivity measured at 16min interval, except for firt 2 hours, every 4 minutes
Levin and Straat; 1977
Labeled Release Results
• Addition of aqueous solution with radioactive organic
compounds, rapid release of labeled gas
• Process eliminated by prior heating at 160°C for 3h - Just
reduced by 45°C and 50°C
• Each time additional liquid, 30% of labeled gas went into
solution
• Storage of sample for 2 to 4 months eliminated agents,
responsible for rapid decomposition of nutrient
• Interpreted persumptive biological
Labeled Release Results
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Problems: reaction so rapid so intense – large biological load needed:
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Analogy with Escherichia coli: 3.2 x 106 cells
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90% organic subtrates unattacked
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No basis interpretation of uptake of labeled gas upon wetting
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Suggestion of oxidizing compounds cannot be ignored
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But oxides not responsible, because:
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No direct correlation between capacity of sample to yield O2 becoming wet and ability to decompose nutrient
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More sensitive to prior heating than the O2 generating reaction is.
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Storage loss of activity, but not in Gex
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Another oxidant which does not generate O2 reaction
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Maybe pH change of nutrient upon contact with soil – no oxidantion of nutrients (but neutral pH required, but samples
alcaline)
Oxidant: heat resitant, not destroyed by storage
Pyrolytic Release Experiment
• Life on Mars could be photosynthetic and incorporate carbon as biomass
through carbon fixation which is provided as 14C
• Assumption: Martians assimilate CO2 and CO from atmosphere and
convert these to organic matter, conditions on Mars as closely as possible
• Inkubation in light and dark for 5 days
• Illumination wavelength below 320 nm filtered out (Xenon light)
• Inkubation temperature 10-18°C
• Weak but persumptive positives
• Only heterotrophic may be present
Carbon assimilation
Experiment
Pyrolitic Release Results
• Significant positives
• Prior heating at 175°C for 3h cut down , but not completely the
reaction, heating upto 90°C no deleterious effect
• Reaction better in light
• Storage did not reduce capacity
• Sample first humidified, after cell heated, vented, dry out -> should
remove oxidants
• But sample still positive
• Catalyst must be stable at 90°C but not at 175°C
Reanalysis …
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CH3Cl detected by Viking 2 (2-40ppb) – terrestrial?
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No Cl measured -> reacted with Ni oven?
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Soil perchlorate burns organics into CO2
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500g Yungay Valley (10cm upper soil)
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Magnesium perchlorate – extended T: 200°-1000°C
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Results:
– H2O most abundant, at 1000°C (small fraction of oxidation of organics?)
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CO2 second abundant: (1) amtospheric absorption (≤200°C); (2) oxidation of organic matter at ≥ 200°C; (3)
thermal decomposition of carbonates at ≥ 450°C
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O2 third abundant gas at 750°C (dehydroxylation of clay minerals (≤ 350°C) and decomposition of nonmetal
(C,N,O,P,S,Cl))
Reanalysis…
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Viking discrepance:
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Viking detected CH3Cl at 200°C at 15ppb levels but not above 200°C – terrestrial contamination
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Navarro et al. CH3Cl is produced above 350°C; detection ability of GCMS?
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Martian chlorine mass fragments 50 to 52 = 3:1; corresponding terrestrial 37Cl/35Cl isotopic ratio =0.319
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Resevoir of chlorine species is presolar nebulae -> ratio same on Mars as on Earth
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Viking 1 0.1wt% and Viking 2 0.9 wt% chlorine
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Rapid combustion and chlorination of methane in TV oven, but had organics at 40 ppb, instantaneously
released, when soil heated -> 15 ppb chloromethane indicates high level of carbon: 1.5 ppm at 0.1% wt
perchlorate and 6.5 ppm at 0.01% perchlorate
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Viking did not measure CO2 by TV step.
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Viking 2 detected dichloromethane at 200° with 0.04 – 0.08 ppb - > organic carbon required 50-500 ppm
Perchlorate on Mars
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Phoenix measured 0.4 to 0.6% of perchlorate in 1mM dissolved salts
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Wet Chemistry Labor measured solution concentration of cations, ions and halide ions, intended to monitor nitrate,
but used for perchlorate detection
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Perchlorate ion average concentration level of 2.4 (+-0.5)mM
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If perchlorate produced photochemical like on Earth and chlorine direct from volcanic gas -> perchlorates only later
geologic time, because, early Mars had reducing atmosphere
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Production not fully understood
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Ozone, hydroxyl radicals as oxidizer for sodium chloride from the sea and are somewhat similar to the formation
processes of iodates also present in the atmosphere
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On Earth: 0.03 – 0.6 wt% at Atacama
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Chlorine oxides generated from chlorine inputs to atmosphere, reactions with O3 -> HClO4 -> deposit on ground:
– OCLO + O3 -> ClO3 +O2
– OH + ClO3 + M -> HClO4 + M
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Sources of Clorine: Volcanic HCl
HClO4 in Stratosphere 0.5-5 ppt in sulfate aerosols
Perchlorate on Mars
• On Mars:
– Photochemistry generates oxidizing species (H2O2 and O3, OH, HO2, O)
– Ultraviolett action on minerals produce free radicals
– 2 Chlorine sources: Volatile chlorine in past as volcanic HCl and also acid displacement
reactions with salts in acidic near surface aqueous environmets (CaCl2 + H2SO4 = 2HCl+
CaSO4)
– If Cl from volcanism: ~ 108 mol HCl /yr over 1 Myr = 1 wt% Mg(ClO4)2 in 10 cm of soil
(1g/cm³) over 10 % of Mars surface
– Chlorine gas may also sourced by aerosols: OH radicals react at the deliquesced watergas interface of seasalt particles to release chlorine
– If Mg(ClO4)2, production: 1,2 x 10-9 mol cm-2 yr-1 -> possible effects?
– If 1wt% Mg(ClO4)2 at phoenix -> age must be younger than 0.2 Myr -> Volcanic activity?
Hydrazine
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22 kg propellants left at landing
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18 nozzles to spread hydrogen, nitrogen over wide area
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40 sec fired
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Surface heating 1°C; 1mm material stripped away
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45% NH3 (ca. 10 kg left at landing)
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Rest: H2 and N2 …… N2 + 3H2 -> 2 NH3
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Hydrazine 0.2%
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Recombination of N2 and H2 to NH
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Possible effects: Redoxreaction with Hydrogenperoxide or superoxides?
Referenzen:
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Klein, Horowitz, Levin, Oyama et al.; 1976
Klein; 1978
Klein; 1998
Levin and Straat; 1977
Levin and Straat; 1981
Oyama and Hubbard; 1977
Plemmons et al.; 2008
http://nssdc.gsfc.nasa.gov/planetary/viking.html
http://www.bernd-leitenberger.de/viking.shtml
http://www2.jpl.nasa.gov/basics/viking.html
http://de.wikipedia.org/wiki/Viking