In Chapter 4, I stated that ‘interstellar matter provides the raw material for the formation of stars and planets’ and it should now be evident that interstellar matter may well have also been important starting material for the origin of life on Earth (Bernstein, 2006; Chyba et al., 1990; Ehrenfreund & Cami, 2010; Ehrenfreund et al., 2002). In fact, in Hazen’s phrase:

This being the case, and as there are so many plausible mechanisms for the synthesis of biogenic compounds in situ on planet Earth, it is surprising that so much attention has been given to the possibility that life came to Earth ready formed rather than originating here. The panspermia hypothesis claims that life exists throughout the Universe, with microbes drifting through interstellar and interplanetary space, transmitting life to the next habitable body they encounter. According to this view the Earth of long ago was colonised by microbes that had somehow escaped from their home planets to drift across the vast distances between the stars until they arrived on that primeval and sterile Earth. Panspermia should not be confused with pangenesis; the latter was Charles Darwin’s conjectural mechanism to explain heredity (he argued that inheritance depended on particles produced by each organ being transmitted from parent to offspring).