Raina Gough
B.S., Chemistry, 2004
Ph.D., Chemistry, 2010
A plume of methane detected during the northern Martian summer, 2004. |
Laboratory studies of the heterogeneous chemistry of trace gases on Mars
We are interested in heterogeneous (gas-surface) processes that may be occurring on Mars. Specifically, we are currently experimentally investigating possible reactions of methane with Martian analog soils. Recently, small amounts of methane (~10 ppbv) were detected in the Martian atmosphere. It has been suggested that this methane is also spatially and temporally variable, with possible seasonal correlations. These observations are surprising for many reasons: first, the source of the methane is not known. Is it ancient methane slowly degassing from subsurface reservoirs or ices? Geological processes such as reactions between liquid water and rocks? Or possibly even some form of life, such as methanogenic bacteria?
The highly variable methane presents another mystery: where is the methane going? In order to reproduce the observations, global climate models have shown that the methane needs to be destroyed very quickly, about 100 times faster than the known loss processes (gas phase photolysis and oxidation) can occur. It is suspected that the cause of the methane variability is an unidentified heterogeneous reaction with the Martian surface. It has been known since the Viking mission in the 1970’s that the Martian soil is highly oxidizing. However, the specific oxidizing agent, the reaction mechanism and rates and the depth of soil reactivity are all still unknown. We are currently conducting experiments under simulated Martian conditions to try to determine possible methane loss processes, either temporary or permanent, that may be occurring on Mars.
Vacuum chamber used to simulate Martian temperatures and pressures
Publications:
1. Gough, R.V., J.J. Turley, G.R. Ferrell, K.E. Cordova, S.E. Wood, D.O. DeHaan, C.P. McKay, O.B. Toon, and M.A. Tolbert, Can rapid loss and high variability of Martian methane be explained by surface H2O2? Planetary & Space Science, 2011. 59(2-3): p. 238-246.
2. Meslin, P.Y., R. Gough, F. Lefèvre, and F. Forget, Little variability of methane on Mars induced by adsorption in the regolith, Planetary & Space Science, 2011. 59(2-3): p. 247- 258.
3. Gough, R., V. Chevrier, K. Baustian, M. Wise, and M. Tolbert. Metastable Aqueous Perchlorate Solutions at the Phoenix Landing Site: Experimental Studies Of Phase Transitions Relevant To Mars, American Astronomical Society, DPS meeting #42, 2010. Pasadena, CA.
4. Gough, R.V., M.A. Tolbert, C.P. McKay, and O.B. Toon, Methane adsorption on a Martian soil analog: An abiogenic explanation for methane variability in the Martian atmosphere. Icarus, 2010. 207(1): p. 165-174.
5. Hatch, C.D., R.V. Gough, O.B. Toon, and M.A. Tolbert, Heterogeneous nucleation of nitric acid trihydrate on clay minerals: Relevance to Type Ia polar stratospheric clouds. Journal of Physical Chemistry B, 2008. 112(2): p. 612-620.
6. Hatch, C.D., R.V. Gough, and M.A. Tolbert, Heterogeneous uptake of the C-1 to C-4 organic acids on a swelling clay mineral. Atmospheric Chemistry and Physics, 2007. 7(16): p. 4445-4458. |
Current Tolbert Group
Where are they now?
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