Earliest Evolved Rocks: A Solar System Perspective

Granitic rocks dominate Earth's continental crust, yet the Hadean record is severely limited. Extraterrestrial evolved lithologies, crystallized under anhydrous, plate tectonics-free conditions analogous to those of early Earth, provide valuable analogues. This review synthesizes lunar, asteroidal, Martian, and candidate Venus/Mercury data, revealing that partial melting of mafic protoliths, not fractional crystallization or silicate liquid immiscibility, represents the dominant formation mechanism. Granitic magmatism persisted episodically from merely 2.3 Myr after Solar System formation through at least 3.87 Ga, with estimated abundances of 0.2–2% representing a conservative lower limit. These findings imply that Hadean Earth possessed the thermal and compositional prerequisites for analogous magmatism, potentially yielding a crustal inventory of 0.2–40% felsic material. By establishing a comparative planetary framework, this study illuminates pathways for reconstructing Earth's earliest crustal evolution and highlights priorities for future exploration missions targeting cryptic silicic reservoirs, particularly deep-crustal exposures in large lunar impact basins and in situ characterization of Venusian highland terrains.