Question

### Prebiotic Chemistry on Titan

Titan, Saturn's largest moon, has a thick atmosphere rich in nitrogen and methane, and a surface containing water ice and lakes of liquid methane and ethane. Two scientists discuss where prebiotic chemistry (reactions leading to the origin of life) is most likely to occur on Titan.

Scientist 1
Prebiotic chemical pathways on Titan must occur in its surface hydrocarbon lakes. At Titan’s average surface temperature of $-179^\circ\text{C}$, liquid water is completely absent. However, solar ultraviolet radiation photochemically produces complex organic molecules, such as acetylene ($C_2H_2$) and hydrogen cyanide ($HCN$), in the atmosphere. These molecules deposit onto the surface and dissolve in the liquid methane and ethane lakes. In these hydrocarbon solvents, organic molecules can react to form more complex, nitrogen-rich organic polymers. Therefore, these lakes are the primary sites for Titan's prebiotic chemical evolution.

Scientist 2
Prebiotic chemical pathways on Titan must occur in liquid water, which is periodically generated on Titan's surface by meteoroid impacts. When a meteoroid impacts Titan's icy crust, the kinetic energy is converted into heat, melting the ice and creating localized pools of liquid water that can persist for thousands of years before freezing. Atmospheric organic molecules that deposit on the surface dissolve in these impact-generated melt pools. The high reactivity of liquid water enables rapid hydrolysis reactions, converting simple organics into amino acids. Liquid hydrocarbons in Titan's lakes are chemically inert at $-179^\circ\text{C}$ and cannot serve as solvents for prebiotic reactions.

Both Scientist 1 and Scientist 2's arguments rely on which of the following assumptions?