Soru

### Martian Methane

Two scientists discuss the origin and behavior of methane ($CH_4$) detected in the Martian atmosphere. Because methane is rapidly destroyed by solar ultraviolet (UV) radiation (photolysis) with an atmospheric lifetime of approximately 300 years, its ongoing presence requires a continuous or episodic source.

Scientist 1
Martian methane is produced biogenically by methanogenic microbes residing in deep subsurface liquid water reservoirs. These microbes utilize hydrogen ($H_2$) and carbon dioxide ($CO_2$) to produce $CH_4$ and metabolic energy. Geothermal heat warms these deep reservoirs, maintaining liquid water despite Mars's freezing surface temperatures. The methane gradually migrates upward and is released into the atmosphere through seasonal fractures in the overlying cryosphere. The observed seasonal fluctuations in atmospheric methane concentration are directly driven by the metabolic cycles of these microbes, which increase their activity during the warmer Martian summer.

Scientist 2
Martian methane is produced abiogenically via serpentinization, a geochemical process. In the Martian crust, water reacts with olivine-rich volcanic rocks at temperatures of $150^\circ\text{C}$ to $250^\circ\text{C}$, yielding $H_2$. This $H_2$ subsequently reacts with dissolved $CO_2$ via a metal-catalyzed Fischer-Tropsch-type reaction to form $CH_4$. Once formed, the methane is trapped within clathrate hydrates (water ice cages) in the shallow cryosphere. The observed seasonal variations in atmospheric methane are caused solely by the physical sublimation of these clathrate hydrates as summer solar heating warms the shallow subsurface, releasing the trapped gas; biological processes play no role in Martian methane dynamics.

Based on the viewpoints of Scientist 1 and Scientist 2, the scientists disagree on which of the following questions?