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

1

• Start: August 20, 1975

• Ankunft: June 19, 1976

• Landung: July 20, 1976

• Ort: Chryse Planitia

(22.48° N, 49.97° W)

• Last Contact: November 13, 1982

2

• Start: September 9, 1975

• Ankunft: August 7, 1976

• Landung: September 3, 1976

• Ort: Utopia Planitia

(47.97° N, 225.74° W)

• Last Contact: April 11, 1980

Spacecraft & Instruments

• Bioshield - prevent contamination

• 2 radioisotope thermal generator (RTG) units (plutonium 238)

• 4 x 28 volt rechargeable batteries

• Propulsion - Deorbit monopropellant

hydrazine (N2H4) rocket

• Landing: 3 Monopropellant hydrazine

engines (120°) 18 nozzles (276 -2667N)

• Hydrazine purified; 85 kg

Viking Lander

• 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

Primary scientific objectives:

Biology

Chemical composition (organic and inorganic)

Meteorology

Seismology

Magnetic properties

Physical properties of martian surface and atmosphere

The Biological Load - GCMS• Gas Chromatograph – Mass

spectrometer

• Mass: 19.0 kg

• Meassuring ppb

• Mass: 15.0 kg

• Search Martian organisms by metabolic products

GCMS• 1) sample crushed and heated up in oven

625°C -> Gas transferred with H2

• 2) Gas from soil sample and carrier gas stream through GC filtersystem

• 3) filtered Gas in seperator, pressureregulation, seperator of Palladium-alloy, leadsto discharge of hydrogen

• 4) Mass-Spectrometer: Gas molecules in high–voltage field leads to ionization, magneticlense focusing to a small beam

• 5) Ionized Gas pass Magnetic field, chemicalcomponents aligned according to theirmolecular weight

• 6) Electron-multiplier, chemical analysistransformed into electrical signs

1 2

3

4

56

Gas Exchange ExperimentHumid Mode

– Humid Nonnutrient mode: Martians are waiting dorment in the dry martian soil until enough moisture -> stimulatingmetabolism -> Atmosphere analysed by GC

Sol (24h 39min 35,244 sec syn.) is limiting factor for growth ofmartian 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 saturationof atmosphere with water, incubation temperatur between 8-15°C, test: 7 days

– Test once by each Lander

Gas Exchange ExperimentWet Nutrient Mode

• Significant fraction of Martian biota is heterotrophic

• Addition of organic compounds necessary for metabolicresponse (only in aqueous environment)

• Large number of different organic and inorganic compounds

• Experiment 3 times:– 200sol VL1 inkubation 13 sols– 31 sol VL2 inkubation 19 sols– 116 sol VL2 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

• Humid mode:– CO2 and N2 desorbed from soil, rapid

accumulation of oxygen

– Release of oxygen never seen before

– Poorly understood and very rapid (2 ½ hour)

– later addition of water no more reaction, further in dark, so no biological explanation

– Same reaction in preheated „sterilized“ sample

– Hydrogenperoxide unlikely, because not survived heating

• Wet mode:– after contact, 30% of CO2 went into solution

– CO2 slowly continually produced, returned to original level and increased with time

– No other gas changes of biological origin

– Absorption of CO2 also in sterilizied samples

– After nutrient drained out and fresh added, production rate of CO2slowed down each time

– Reactions also seen in sterile terrestrial samples

– Uptake of CO2 from Metal oxides, hydroxides, created by interaction of water with peroxides, superoxides

– γ-Fe2O3 nutrient oxidizing by secondary oxidant, likeiron oxide

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 neededmonths!

• High atmospheric pressure

Labeled Release Experiment

• Assumption: heterotrophic organisms on Mars, capable of decomposingone 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 smallvolume 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 minutesLevin and Straat; 1977

Labeled Release Results

• Addition of aqueous solution with radioactive organiccompounds, 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 intosolution

• Storage of sample for 2 to 4 months eliminated agents, responsible for rapid decomposition of nutrient

• Interpreted persumptive biological

Labeled Release Results• Problems: reaction so rapid so intense – large biological load needed:

– Analogy with Escherichia coli: 3.2 x 106 cells

– 90% organic subtrates unattacked

– No basis interpretation of uptake of labeled gas upon wetting

– Suggestion of oxidizing compounds cannot be ignored

– But oxides not responsible, because:

• No direct correlation between capacity of sample to yield O2 becoming wet and ability to decompose nutrient

• More sensitive to prior heating than the O2 generating reaction is.

• Storage loss of activity, but not in Gex

• Another oxidant which does not generate O2 reaction

• Maybe pH change of nutrient upon contact with soil – no oxidantion of nutrients (but neutral pH required, but samplesalcaline)

• Oxidant: heat resitant, not destroyed by storage

Pyrolytic Release Experiment

• Life on Mars could be photosynthetic and incorporate carbon as biomassthrough carbon fixation which is provided as 14C

• Assumption: Martians assimilate CO2 and CO from atmosphere andconvert 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 assimilationExperiment

Pyrolitic Release Results

• Significant positives

• Prior heating at 175°C for 3h cut down , but not completely thereaction, 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 -> shouldremove oxidants

• But sample still positive

• Catalyst must be stable at 90°C but not at 175°C

• CH3Cl detected by Viking 2 (2-40ppb) – terrestrial?

• No Cl measured -> reacted with Ni oven?

• Soil perchlorate burns organics into CO2

• 500g Yungay Valley (10cm upper soil)

• Magnesium perchlorate – extended T: 200°-1000°C

• Results:

– H2O most abundant, at 1000°C (small fraction of oxidation of organics?)

– CO2 second abundant: (1) amtospheric absorption (≤200°C); (2) oxidation of organic matter at ≥ 200°C; (3) thermal decomposition of carbonates at ≥ 450°C

– O2 third abundant gas at 750°C (dehydroxylation of clay minerals (≤ 350°C) and decomposition of nonmetal(C,N,O,P,S,Cl))

Reanalysis …

Reanalysis…

• Viking discrepance:

– Viking detected CH3Cl at 200°C at 15ppb levels but not above 200°C – terrestrial contamination

– Navarro et al. CH3Cl is produced above 350°C; detection ability of GCMS?

– Martian chlorine mass fragments 50 to 52 = 3:1; corresponding terrestrial 37Cl/35Cl isotopic ratio =0.319

– Resevoir of chlorine species is presolar nebulae -> ratio same on Mars as on Earth

– Viking 1 0.1wt% and Viking 2 0.9 wt% chlorine

– Rapid combustion and chlorination of methane in TV oven, but had organics at 40 ppb, instantaneouslyreleased, when soil heated -> 15 ppb chloromethane indicates high level of carbon: 1.5 ppm at 0.1% wtperchlorate and 6.5 ppm at 0.01% perchlorate

– Viking did not measure CO2 by TV step.

– Viking 2 detected dichloromethane at 200° with 0.04 – 0.08 ppb - > organic carbon required 50-500 ppm

Perchlorate on Mars • Phoenix measured 0.4 to 0.6% of perchlorate in 1mM dissolved salts

• Wet Chemistry Labor measured solution concentration of cations, ions and halide ions, intended to monitor nitrate, but used for perchlorate detection

• Perchlorate ion average concentration level of 2.4 (+-0.5)mM

• If perchlorate produced photochemical like on Earth and chlorine direct from volcanic gas -> perchlorates only latergeologic time, because, early Mars had reducing atmosphere

• Production not fully understood

• 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

• On Earth: 0.03 – 0.6 wt% at Atacama

• Chlorine oxides generated from chlorine inputs to atmosphere, reactions with O3 -> HClO4 -> deposit on ground:

– OCLO + O3 -> ClO3 +O2

– OH + ClO3 + M -> HClO4 + M

• 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 displacementreactions 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 water-gas 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

• 22 kg propellants left at landing

• 18 nozzles to spread hydrogen, nitrogen over wide area

• 40 sec fired

• Surface heating 1°C; 1mm material stripped away

• 45% NH3 (ca. 10 kg left at landing)

• Rest: H2 and N2 …… N2 + 3H2 -> 2 NH3

• Hydrazine 0.2%

• Recombination of N2 and H2 to NH

• Possible effects: Redoxreaction with Hydrogenperoxide or superoxides?

Referenzen:

• 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