Soru

Martian Methane Spikes

In 2019, planetary probes detected sudden, seasonal spikes in the concentration of atmospheric methane ($\text{CH}_4$) on Mars, which peaked during the Martian summer. Two scientists propose different explanations for these observations.

Scientist 1
The methane spikes are biogenic in origin, produced by subterranean methanogenic microbes. During the Martian summer, warmer surface temperatures melt subsurface permafrost, allowing the microbes to increase metabolic activity and release accumulated methane gas into the atmosphere. Because biological metabolic processes are highly selective, methanogens preferentially utilize carbon-12 ($^{12}\text{C}$) over carbon-13 ($^{13}\text{C}$), producing methane that is highly enriched in $^{12}\text{C}$ relative to $^{13}\text{C}$. Furthermore, biological methanogenesis produces almost exclusively methane, with negligible amounts of heavier hydrocarbons like ethane ($\text{C}_2\text{H}_6$) or propane ($\text{C}_3\text{H}_8$).

Scientist 2
The methane spikes are abiogenic (geochemical) in origin, resulting from serpentinization—a reaction between water, carbon dioxide ($\text{CO}_2$), and olivine minerals deep within the Martian crust. The gas is trapped in subsurface ice structures called clathrates. During the Martian summer, increased solar radiation warms the shallow crust, melting the clathrates and releasing the trapped gas. Serpentinization is a high-temperature geochemical process that does not preferentially select light carbon isotopes, resulting in methane with standard planetary ratios of $^{12}\text{C}$ to $^{13}\text{C}$. Additionally, serpentinization naturally produces significant quantities of ethane and propane alongside methane.

Which of the following new experiments or measurements would provide the best evidence to resolve the conflict between the two scientists' viewpoints?