The short answer
- For all we know, a natural origin of life could have been rapid enough to occur after the Hadean era.
- There are areas on Earth that would have been suitably protected during the Hadean era.
- Part of the process may have occurred in space before or during the Hadean era.
The longer answer
The Hadean era is an informal era spanning around 4.5 – 4 billion years ago. The earliest record of life is 3.8 billion years old. During the Hadean era, the surface of the Earth was molten and constantly bombarded by meteorites, though water was present for most of the time. The worry is that conditions during the Hadean era were too inhospitable to allow any steps toward life, and that the window after the Hadean is too small for it.
II. The origin of life may have been rapid.
Even if life had only a small window of time in which to arise, this would not rule out a natural origin of life: many live avenues of research propose relatively rapid-acting mechanisms. According to Stanley L. Miller (he of the famous Miller-Urey experiments) life may even have come into being within “a period of perhaps 10,000 years” (Miller 1992:3).
III. Protected regions
There are areas on Earth that would have been spared the worst of the bombardment during the Hadean area. For example, deep-sea vents would have been spared, and some researchers already believe these to have been important to the origin of life for independent reasons. (Fry 2000:19).
IV. Prebiotic synthesis in space
Some prebiotic synthesis (synthesis of the chemicals of life before life actually existed) may also have been accomplished in space, and then delivered to Earth by meteorites, shortening the time needed on Earth for the origin of life. Molecules important for abiogenesis that have been detected in space include hydrogen cyanide, formaldehyde, and cyanoacetylene (Olomucki 1993:46); amino acids and sugars also have been found on meteorites.
Fry I. 2000. The Emergence of Life on Earth: A Historical and Scientific Overview. New Brunswick: Rutgers University Press.
Miller SL. 1992. The prebiotic synthesis of organic compounds as a step toward the origin of life. pp. 1-28 in Schopf 1992
Olomucki M. 1993. The Chemistry of Life. New York: McGraw-Hill.
Schopf JW (ed). 1992. Major Events in the History of Life. Boston: Jones and Bartlett.