Question

### Sources of Martian Methane

Methane ($CH_4$) gas detected in the atmosphere of Mars has sparked debate regarding its origin. Because $CH_4$ is rapidly destroyed by solar radiation and chemical reactions in the Martian atmosphere, any detected methane must have been recently released. Two models have been proposed to explain the origin of this methane.

* Model 1 (Biogenic Source): Methane is produced by subsurface methanogenic microorganisms. These microbes use carbon dioxide ($CO_2$) and hydrogen ($H_2$) to produce energy, releasing $CH_4$ as a metabolic waste product. The microbes inhabit deep liquid water reservoirs where temperatures are warm enough for cellular activity. As crustal temperatures rise during the Martian summer, pressure gradients push the accumulated gas through seasonal fissures in the soil and into the atmosphere.
* Model 2 (Abiogenic Source): Methane is produced through serpentinization, an inorganic geochemical reaction between water ($H_2O$), dissolved carbon dioxide ($CO_2$), and olivine minerals in the Martian crust. This reaction occurs at high temperatures (typically above $100^\circ\text{C}$) in deep, geologically active zones. The produced $CH_4$ is trapped inside sub-surface water-ice cages called clathrate hydrates. During seasonal warming, the thermal decomposition of these hydrates releases $CH_4$ gas, which migrates to the surface.

Planetary scientists have collected new experimental observations and data from Martian orbiters and rovers. Match each of the new findings on the left to the statement on the right that best describes how that finding supports or contradicts the proposed models.