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Organic degradation under simulated Martian conditions
1Space Science Division, NASA Ames Research Center, Moffett Field, California, USA.
Journal of Geophysical Research
|May 25, 1997
Summary
Organic compounds on Mars break down rapidly due to UV radiation, faster than meteorites deliver them. This explains the lack of organics found by Viking, without needing oxidants.
Area of Science:
- Astrobiology
- Planetary Science
- Organic Geochemistry
Background:
- Understanding the fate of organic molecules on Mars is crucial for assessing habitability.
- Previous findings of no organic compounds by Viking missions suggested strong oxidants, but alternative explanations are explored.
Purpose of the Study:
- To simulate and quantify the decomposition of organic compounds under Martian surface conditions.
- To determine if abiotic degradation can explain the absence of organics detected by Viking.
Main Methods:
- Laboratory experiments using Mars-analog soil and glycine.
- Irradiation with a broad-spectrum Xe lamp simulating solar radiation.
- Analysis of decomposition products via gas chromatography.
Main Results:
- Measured quantum efficiency for glycine decomposition at 2000-2400 angstroms was 1.46 x 10^-6 molecules/photon.
- Scaled organic destruction rate on Mars is 2.24 x 10^-4 g C m^-2 yr^-1.
- Organic destruction rate exceeds deposition rate from meteoritic infall.
Conclusions:
- Abiotic degradation by UV radiation sufficiently explains the lack of organic compounds on Mars.
- The organic destruction rate provides an upper bound for potential Martian biomass production.
- Organic compounds may be more stable than calcite under current Martian surface conditions.