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Martian CH(4): sources, flux, and detection
T C Onstott1, D McGown, J Kessler
1Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA. tullis@princeton.edu
Astrobiology
|May 13, 2006
Summary
Methane on Mars may originate from subsurface geological or microbial sources. A new model suggests hydrate sublimation could explain observed atmospheric methane, while microbial production might be less significant.
Area of Science:
- Astrobiology and Planetary Science
- Geochemistry
- Atmospheric Science
Background:
- Trace amounts of methane (CH4) have been detected in the Martian atmosphere, indicating a subsurface flux.
- Potential sources include volcanism, hydrate ice sublimation, cryosphere transport, and microbial generation.
- Understanding the origin of Martian methane is crucial for assessing habitability and geological activity.
Purpose of the Study:
- To develop a diffusive flux model for gases (Helium, Hydrogen, Methane) in the Martian crust.
- To differentiate between abiogenic and microbial methane sources using isotopic composition.
- To evaluate the potential contribution of various sources to the observed atmospheric methane.
Main Methods:
- Developed a diffusive flux model based on deep fracture water samples.
- Coupled microbial methane production to hydrogen generation via water radiolysis.
- Analyzed potential methane fluxes under different cryosphere conditions (hydrate saturation).
Main Results:
- The model predicts abiogenic methane flux of ~10^6 cm^2 s^-1 and microbial flux of ~10^9 cm^2 s^-1 for a Helium flux of ~10^5 cm^2 s^-1.
- Methane flux reaches the surface only if the cryosphere is saturated with methane hydrate; otherwise, it is captured.
- Sublimation of hydrate-rich cryosphere can explain observed methane flux; microbial production above the hydrate zone is less significant (~10^5 cm^2 s^-1).
Conclusions:
- The isotopic composition of methane (CH4) and ethane (C2H6) can distinguish between different sources.
- Cavity ring-down spectrometers are suitable for future rover missions to measure isotopic values and pinpoint methane sources.
- Further investigation is needed to confirm the origin of Martian methane and its implications for life.
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