Presentation Title

Laboratory Studies of the Heterogeneous Uptake of Methane in the Martian Atmosphere

Faculty Mentor

Fred Grieman

Start Date

18-11-2017 1:30 PM

End Date

18-11-2017 1:45 PM

Location

9-263

Session

Physical Sciences 3

Type of Presentation

Oral Talk

Subject Area

physical_mathematical_sciences

Abstract

Accurate modeling of methane, an important biological proxy, is highly complementary to the search for extra-terrestrial life. On Mars, methane levels are far lower than expected, and have unpredictable spatiotemporal variance. Perchlorate based oxidation, in the presence of UV radiation, has recently been proposed as a mechanism for methane decomposition. In this analysis, FT-IR was used to study the time-series UV photolysis of magnesium perchlorate (Mg(ClO4)2) and the subsequent UV mediated reaction between Mg(ClO4)2 and CH4. We implicate a number of different products in the photolysis reaction including gaseous Cl2O4 and Cl2O6 as well as surface Mg(ClO3)2; further tentative assignments have been made for ClO2 and HClO4. These assignments have been confirmed via ab initio calculations of vibrational energies using the B3LYP DFT method. Furthermore, preliminary analysis of the methane-based reaction indicates the evolution of carbon dioxide gas, suggesting the potential of the UV active Martian regolith to produce reactive chlorine oxides with the ability to oxidize methane. Ultimately, the goal of this work is to use time-series FT-IR based measurements to estimate the radiolytic decay constant for the heterogeneous uptake of methane on perchlorate surfaces in order to inform future atmospheric modeling and land-based experiments.

Summary of research results to be presented

- Surface reduction of magnesium perchlorate to magnesium chlorate.

- Detection of various chlorine oxide products including Cl2O4, Cl2O6 and ClO2.

- Result that methane is oxidized by UV active perchlorate surfaces.

- Quantification of CO2 formed via methane oxidation.

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Nov 18th, 1:30 PM Nov 18th, 1:45 PM

Laboratory Studies of the Heterogeneous Uptake of Methane in the Martian Atmosphere

9-263

Accurate modeling of methane, an important biological proxy, is highly complementary to the search for extra-terrestrial life. On Mars, methane levels are far lower than expected, and have unpredictable spatiotemporal variance. Perchlorate based oxidation, in the presence of UV radiation, has recently been proposed as a mechanism for methane decomposition. In this analysis, FT-IR was used to study the time-series UV photolysis of magnesium perchlorate (Mg(ClO4)2) and the subsequent UV mediated reaction between Mg(ClO4)2 and CH4. We implicate a number of different products in the photolysis reaction including gaseous Cl2O4 and Cl2O6 as well as surface Mg(ClO3)2; further tentative assignments have been made for ClO2 and HClO4. These assignments have been confirmed via ab initio calculations of vibrational energies using the B3LYP DFT method. Furthermore, preliminary analysis of the methane-based reaction indicates the evolution of carbon dioxide gas, suggesting the potential of the UV active Martian regolith to produce reactive chlorine oxides with the ability to oxidize methane. Ultimately, the goal of this work is to use time-series FT-IR based measurements to estimate the radiolytic decay constant for the heterogeneous uptake of methane on perchlorate surfaces in order to inform future atmospheric modeling and land-based experiments.