Table 2.

Proposed Environments for the Origin of Life on Earth Due to Endogenic Processes and Equivalent Impact-Generated Origin

Environment	Endogenic origin*	Impact-generated origin?
Submarine hydrothermal vents	Active at the present day along oceanic spreading ridges (black smokers) and along off-ridge spreading centers (white smokers) (i.e., due to plate tectonics). Proposed to have formed in the Hadean due to higher heat flow in crust driving abundant volcanic activity.	Formed due to impact-generated hydrothermal activity in marine impact craters. Venting around faulted crater rims and central uplifts documented in the literature.
Subaerial hot springs and geysers	Subaerial hot springs and geysers found in various continental settings. Heat sources include plate tectonic-derived volcanism, mantle hotspots, and radioactive decay.	As above for impacts on land. Creation of subaerial hot springs also possible for marine impacts, where the impact process leads to uplift of crater rims and central uplift (central peak and peak rings).
Volcanic splash pools	Formation of rock pools on newly formed lava flows in coastal volcanic environments.	Formation of rock pools on newly formed impact melt flows in coastal marine and crater lake environments.
Hydrothermal-sedimentary context	Hydrothermal fluid flow through the sedimentary layer between oceanic crust and seawater. Hydrothermal fluids derived from crust from volcanic activity.	Hydrothermal fluid flow through intra-crater sediments overlying impact melt rocks and breccias. Driven by impact-generated hydrothermal system.
Pumice rafts	Highly vesicular volcanic glass formed silica-rich (felsic) magmas during explosive volcanism. Volcanism during Hadean largely basaltic with small amounts of felsic volcanism proposed.	Pumice-like material formed during impact events and emplaced within and around craters as clasts in breccias.

^*See Westall et al. (2018) and references therein.