Soru

### Martian Methane Detection

Methane ($CH_4$) in the Martian atmosphere is destroyed by solar ultraviolet (UV) radiation within approximately $300\text{ years}$. Because $CH_4$ has been repeatedly detected in low concentrations, scientists debate the source of this gas.

Scientist 1
Methane on Mars is produced by active microbial life. Methanogens (anaerobic microorganisms) living in deep, warm underground aquifers utilize carbon dioxide ($CO_2$) and hydrogen ($H_2$) to produce $CH_4$ and water. These microbes are shielded from lethal surface radiation. The methane they produce is released into the atmosphere through surface fractures. The observed seasonal fluctuations in methane concentration correspond to temperature-driven microbial metabolic cycles.

Scientist 2
Methane on Mars is produced by geological processes, specifically *serpentinization*. In this process, liquid water reacts chemically with olivine (an iron-magnesium silicate mineral) in the Martian crust, producing serpentine minerals, hydrogen gas, and magnetite. The hydrogen then reacts abiotically with dissolved $CO_2$ via the Fischer-Tropsch-type reaction to form $CH_4$. This methane is stored in subterranean ice cages called clathrates. It is released into the atmosphere during seasonal warming, which fractures the overlying ice.

Scientist 3
Methane is produced by the photolysis of organic material delivered to the Martian surface by micrometeorites. Approximately $2,000\text{ metric tons}$ of cosmic dust and carbonaceous meteoroids enter the Martian atmosphere annually. When solar UV radiation strikes the organic carbon compounds on these meteoroids deposited on the Martian soil, $CH_4$ is synthesized. Because the meteoroid influx is relatively constant, the seasonal variations in atmospheric methane are caused by variations in atmospheric wind patterns and UV intensity, not by geological or biological cycles.

According to Scientist 3, the presence of methane in the Martian atmosphere is primarily a direct result of which of the following processes?