Impact frustration of the origin of life.

One possible definition for the origin of life on Earth is the time at which the interval between devastating environmental insults by impact exceeded the timescale for establishing self-replicating proto-organisms. A quantitative relationship for the Hadean (pre-3,800 Myr ago) and Early Archean (3,800 to 3,400 Myr) impact flux can be derived from the lunar and terrestrial impact records. Also, the effects of impact-related processes on the various environments proposed for abiogenesis (the development of life through chemical evolution from inorganic materials) can be estimated. Using a range of plausible values for the timescale for abiogenesis, the interval in time when life might first have bootstrapped itself into existence can be found for each environment. We find that if the deep marine hydrothermal setting provided a suitable site, abiogenesis could have happened as early as 4,000 to 4,200 Myr ago, whereas at the surface of the Earth abiogenesis could have occurred between 3,700 and 4,000 Myr.