In August 1881 the journal "Science" published an article with a letter exchange by two amateur geologists - British Charles R. Darwin and the German Otto Hahn- discussing the possibility of extraterrestrial life. Just some years earlier Darwin had published a book "On Origin of Species" proposing that complex life forms descended slowly over time from simple ones, however as earth seemed to be too young (based on the erroneous calculations of a certain physicist known today as Lord Kelvin) to explain the observed modern complexity, the origin of microorganisms in space (which existence would predate the formation of earth) could solve this apparent contradiction.
Life from outer space was not a new idea. Already in 1865 the German physician Hermann Eberhard Richter argued that life was an intrinsic property of the cosmos, transported in space on smaller rocky fragments, dormant microorganism could act like seed, evolving in short time into complex organisms after the host-rock impacted on a suitable planet.
Otto Hahn (1828-1904) was a former lawyer turned to amateur naturalist and geologist, with a special interest in the origin of life. Hahn was known by the scientific community due his research on Eozoön or Eozoon (the "dawn animal") - an enigmatic Archaean fossil described in 1864 from Canadian limestone-formations - believed to be some sort of gigantic microorganism it predated all other known fossil organisms. However it seemed strange that already the oldest life form would be a highly evolved animal and Hahn himself doubted that it was even a fossil. In 1880, after carful investigation of some collected rock samples, Hahn changed his mind and reclassified Eozoön as an ancient algae, renaming the fossil Eophyllum ("dawn plant").
Fig.1. Eozoon specimen, the regular lamination were interpretated as chambers of a shelled organism or growth lines, image from DAWSON (1888): The Chain of Life in Geological Time (image in public domain). However in 1894 similar rocks were found in material erupted by Mount Vesuvius, proving that this texture formed by inorganic processes due the alteration of limestone by heat from underground magma.
After this achievement, Hahn suddenly started to find fossils of primitive organisms in all sorts of rocks, not only in sedimentary rocks, but also ancient, partially melted, metamorphic rocks and even igneous rocks like granite or basalt, completely crystallized from the molten magma. He published his observations in a 1879 book entitled "Die Urzelle" - the primordial cell, arguing that in fact all observable rocks were of some sort of sedimentary origin, composed by the shells of these tiny primordial, yet unidentified, microorganisms - and send one copy also to Charles Darwin, inviting him to promote this revolutionary discovery.
Hahn soon added some extraterrestrial material to his collection of microorganism-derived rocks. Not surprisingly, also in samples of meteorites he discovered his primordial cells, also what seemed to be sponges and even corals. He published his discovery in the 1880 book "Die Meteorite (Chondrite) und ihre Organismen" (The chondrite meteorites and their organisms), also one of the first books including images of sections of extraterrestrial rocks. Hahn argued that the studied meteorites were remains of a cosmic cloud of gas, vapor and dust from which our solar system formed. In this semi-liquid environment life formed, evolving at least to the stadium of invertebrates. After the formation of the planets, agglomerated chunks of matter transported these primitive organism onto earth, where they continued to evolve until the appearance of man.
Fig.2. Frontispiece of Hahn's "Die Meteorite (Chondrite) und ihre Organismen" showing a supposed plant- or sponge-like fossil in a meteorite, today reinterpretated as shattered mineral grain (Chondrule), image in public domain.
Also this book was send to Darwin, who - as was his cautious manner - thanked for the gift, replying that the proposed scientific hypothesis was sure worth of further investigation:
"If you succeed in convincing several judges as trustworthy as Professor Quenstedt*, you will certainly have made one of the most remarkable discoveries ever recorded." *[Friedrich August Quenstedt (1809-1889), famous German professor of mineralogy and geology]
However Hahn in a private letter to a friend claimed "Darwin pronounced: it is one of the most important elucidations ever made." Strangely also in the Science article of 1881 other very Darwin-unlike behavior appears. Supposedly Darwin, observing under the microscope the rock fragments, jumped from his seat exclaiming ''Almighty God! What a wonderful discovery! Wonderful!'' and stating that indeed "life [came] down!'' from space.
There survives no hard evidence that Hahn did visit Darwin at Down House in Kent to show him his samples, but it also can't be completely ruled out. Maybe Hahn, before travelling to Canada for his research on Archaean fossils, did also visit England. His idea of all rocks derived from microorganisms, as strange as it may sounds today, was taken serious at the time, at least by some naturalists. However Darwin had studied volcanoes and their igneous products, so there is no doubt he did not share this part of Hahn's visions. Also it seems improbable that Darwin believed it necessary to relocate the origin of life in outer space.
Darwin never addressed in public the mystery of mysteries that is the origin of life. His theory of natural selection deals with the diversification of already reproducing life forms and was never intended (as creationists falsely claim) to explain the origin of life. In private letters he proposed a chemical evolution in a primordial soup, but he also acknowledged that his contemporary science was yet not able to test this hypothesis.
As for the supposed to young age of earth and to evolved terrestrial life forms, already Darwin published various rebuttals to Lord Kelvin's claims in later editions of his "Origin of Species" - there was - so he argued - plenty of time for terrestrial life to evolve, even without extraterrestrial intervention.
PERETO, J.; BADA, J., & LAZCANO, A. (2009): Charles Darwin and the Origin of Life. Origins of Life and Evolution of Biospheres, 39 (5), 395-406
BRASIER, M. (2009): Darwin's Lost World - The hidden history of animal life.Oxford University Press: 304
WYHE, van J. (2010): 'Almighty God! What a wonderful discovery!': Did Charles Darwin really believe life came from space? Endeavour, 34(3): 95-103