In search of historical roots of the extraterrestrial impact theory, II: two unknown German pioneers from the 1850s, Ludwig Pfeil and Karl Reichenbach

The mid-nineteenth century is not regarded as the time when the theory of extraterrestrial catastrophism developed. However, two German scholars independently introduced original concepts of terrestrial impacts of large celestial bodies at that time. Ludwig Pfeil (1803–1896), a self-educated wealthy landowner, and Karl Reichenbach (1788–1869), an eminent scientist and industrialist, independently proposed in the 1850s that the Earth is an aggregate of meteoritic masses and has experienced many impact-induced cataclysms throughout its geological history. Until 1891, Pfeil analyzed the effects of the collision of a comet's gaseous body with Earth. He tried to simulate the effects of tsunami waves generated by impacts into the ocean and inferred the route of “cometary currents” from the morphology and orientation of coastlines and associated mountain ranges. Reichenbach speculated about fertilization of the terrestrial surface by extraterrestrial dust in the context of an accretionary origin for Earth that also manifested in meteoritic sources of volcanic extrusions. He linked the Mesozoic succession of “buried living worlds” to geological catastrophes, caused by successive meteorite impacts. These cosmic bombardment concepts were comprehensively criticized by contemporary researchers, but soon found many conceptual successors in the German-speaking science community. Therefore, Pfeil and Reichenbach should be regarded as pioneers of the impact theory.