Other
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p53a..02c&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P53A-02
Other
[5405] Planetary Sciences: Solid Surface Planets / Atmospheres, [6225] Planetary Sciences: Solar System Objects / Mars
Scientific paper
Introduction: Recent detections of trace gas concentrations in Mars' atmosphere at wavelengths consistent with methane (CH4) [1,2,3,4] raise intriguing questions about the source(s) of that gas, and the desire to more strictly constrain the specific gas(es) being detected. We use the NASA Ames GCM (v. 1.7.3) to investigate surface source magnitudes consistent with the observed gas concentrations, destruction times that can reproduce the seasonality of the observed gas abundances, and other thermodynamic properties of the Mars atmosphere/surface system that might aid in identifying the gas(es) being detected. CH4 was first detected at the 10 ppb level in the Martian atmosphere in 2004 [2,3]. Mumma et al. (2009) have detected spectral features consistent with CH4 and conclude that the abundance changes on a seasonal timescale (observations at Ls 17°, 121°, and 155°) and varies spatially. Their maximum mixing ratio values (~45 ppb at Ls 155°) exceed the values estimated by [2] and [3]. Fonti and Marzo (2009) have investigated three Martian years of MGS TES spectra to reveal a temporally and spatially variable spectral feature at 1306 cm-1 (7.6 μm), coincident with CH4 bands. Their results span a wider seasonal range than those of [1], are globally extensive, and also suggest a northern summer maximum in gas abundance. Lefevre and Forget (2009) have investigated the photochemical destruction time of CH4 using a highly localized and sporadic source in simulations conducted with the Laboratorie de Meteorologie Dynamique GCM. They use episodic releases lasting 60 sols, and show that the spatial and temporal variability in the observations cannot be reproduced without an atmospheric lifetime shorter than 200 days. Our Work: Mumma et al. propose a surface CH4 source magnitude of 0.6 kg s-1 and ~1013 km2 in extent centered in Syrtis Major could diffusively ‘fill’ their observed plume in an appropriate time interval. Simulation results with those source specifications produce column gas mixing ratio values an order of magnitude less than detected [1]. This result arises because the simulated advection of the introduced gas is more efficient than the diffusion coefficient suggested [1]. A source magnitude ~30 times more intense produces column abundance values that agree with those of [1], and also produces global column mixing ratio patterns in reasonable agreement with those of [4], except for their preferred Tharsis source region. The above results arise with a destruction time of ~0.5 Earth years, which is consistent with the results of [5]. Source initiation is constrained by [1] and [4] to occur after Ls 17° but prior to early northern summer, and to persist through middle northern summer. We will investigate various CH4 source scenarios, and also other gases which have similar spectral features but potentially other loss mechanisms. References: [1] Mumma M.J. et al. (2009) Science, 323, 1041-1045. [2] Formisano V. et al. (2004) Science, 306, 1758-1761. [3] Krasnopolsky V. et al. (2004) Icarus, 172, 537-547. [4] Fonti S. and Marzo G.A. (2009) Submitted. [5] Lefevre F. and Forget F. (2009) Nature, 460, 720-723.
Chizek Malynda R.
Haberle Robert M.
Kahre M.
Marzo G.
Murphy Ronald J.
No associations
LandOfFree
A Short-Lived Trace Gas in the Martian Atmosphere: A General Circulation Model of the Likelihood of Methane does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A Short-Lived Trace Gas in the Martian Atmosphere: A General Circulation Model of the Likelihood of Methane, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Short-Lived Trace Gas in the Martian Atmosphere: A General Circulation Model of the Likelihood of Methane will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1774311