Question

Silica-rich deposits discovered on Mars have led to competing models regarding their origin. Three scientists propose different mechanisms for how these deposits formed:

Scientist 1
The deposits formed through acid-sulfate leaching. Acidic groundwater ($pH < 3$) containing dissolved sulfate ions flowed through subterranean basaltic rocks. The acidic fluid selectively dissolved and removed elements such as magnesium ($Mg$), iron ($Fe$), and calcium ($Ca$), leaving behind a highly concentrated, insoluble silica residue ($SiO_2 > 90\%$). This process occurred under ambient, low-temperature subterranean conditions.

Scientist 2
The deposits resulted from solfataric alteration. High-temperature volcanic gases ($>200^\circ\text{C}$), specifically sulfur dioxide ($SO_2$) and hydrogen chloride ($HCl$), mixed with water vapor and rose through crustal fractures. This acidic steam reacted with the surrounding rock, vaporizing volatile metals and carrying them away, leaving amorphous silica crusts at the surface outlets (fumaroles).

Scientist 3
The deposits precipitated directly from a surface water body. A highly alkaline, silica-saturated lake filled the crater. As the lake water evaporated under cold, dry conditions, the concentration of dissolved silica exceeded saturation limits. This caused the silica to precipitate out of the solution alongside evaporite minerals like gypsum.

Match each specific geological mechanism to the scientist whose model proposes that mechanism.