Soru

### Early Martian Clays

Phyllosilicates (clay minerals) are widely distributed across the oldest terrains of Mars, dating back to the Noachian epoch (approximately 4 billion years ago). Because clays require water to form, their presence indicates that liquid water was active on early Mars. However, scientists disagree on the environmental conditions under which these clays formed.

Hypothesis 1 (Surface Weathering Model)
Phyllosilicates formed primarily at the Martian surface through the chemical weathering of basaltic rocks by ambient liquid water. During the Noachian epoch, Mars had a dense greenhouse atmosphere composed mainly of carbon dioxide ($CO_2$) and water vapor ($H_2O$). This atmosphere maintained a warm and wet climate, allowing for rainfall, surface runoff, and stable open bodies of water. Basaltic rocks exposed to this precipitation slowly weathered into clays over millions of years.

Hypothesis 2 (Subsurface Hydrothermal Model)
Phyllosilicates formed primarily in the Martian subsurface through hydrothermal alteration. During the Noachian epoch, Mars had a cold, thin atmosphere, and surface water was frozen as ice. However, heat from geothermal processes and frequent meteoroid impacts warmed groundwater, circulating it through fractures in the basaltic crust. This warm subsurface water chemically altered the surrounding rock into clays. The clays were later exposed at the surface by impact excavation and wind erosion.

Based on Hypothesis 1, which of the following atmospheric and environmental conditions was required for the formation of Martian phyllosilicates?