Question

### Origin of Prebiotic Organics on Early Earth

How organic molecules first accumulated on early Earth to facilitate the origin of life remains a central scientific debate. Three scientists present competing hypotheses regarding the primary source of these prebiotic compounds.

Scientist 1
Prebiotic organic molecules were synthesized in interstellar molecular clouds and delivered to Earth via carbonaceous meteorites and comets during the Late Heavy Bombardment. Early Earth's global atmosphere was dominated by non-reducing gases like $CO_2$ and $N_2$, which prevent the endogenous synthesis of organic compounds. Although heavy impacts caused widespread heating, atmospheric modeling shows that larger meteors and cometary dust particles could enter the atmosphere without reaching pyrolysis temperatures, preserving their organic payloads. Once delivered, these molecules required the presence of liquid water on Earth's surface to accumulate, undergo chemical concentration, and polymerize.

Scientist 2
Prebiotic synthesis occurred endogenously at alkaline hydrothermal vents located on the ocean floor. The global atmospheric composition was irrelevant because these vents provided localized, highly reducing environments rich in $H_2$ and $CH_4$ gases. Chemical reactions were driven by geothermal energy and proton gradients between acidic ocean water and alkaline vent fluids, producing simple organic monomers. Any organic compounds delivered by meteorites would have been completely vaporized and destroyed by the extreme temperatures generated during atmospheric entry and hypervelocity surface impacts. However, the presence of liquid water on Earth's surface was essential to act as the primary solvent that dissolved and transported these synthesized monomers away from the vents, allowing them to accumulate in cooler, stable oceanic reservoirs.

Scientist 3
Prebiotic compounds were synthesized in the upper atmosphere through spark discharges (lightning) acting on localized, reducing gas envelopes. While the global atmosphere was non-reducing, frequent subaerial volcanic eruptions released transient clouds of $CH_4$, $NH_3$, and water vapor. Electrical discharges within these volcanic plumes initiated the synthesis of amino acids and other monomers. Hydrothermal vents could not be the source of prebiotic molecules because their high temperatures (greater than $350^\circ\text{C}$) rapidly decompose organic compounds rather than synthesize them. After atmospheric synthesis, liquid water on Earth's surface was required to wash the organic compounds out of the atmosphere, collecting them in shallow pools where they were shielded from destructive solar ultraviolet radiation and could undergo further prebiotic evolution.

Based on the passages, all three scientists would agree with which of the following statements regarding the conditions required for prebiotic organic molecules to accumulate or evolve on early Earth?