Panspermia

Panspermia is the hypothesis that life exists throughout the Universe, distributed by comets, asteroids and even as dessicated microscopic particles.

The theory is not new. The first known mention of the term was in the writings of the 5th century BC Greek philosopher Anaxagoras. In the nineteenth century it was again revived in modern form by several scientists, including Jöns Jacob Berzelius (1834), http://en.wikipedia.org/wiki/Panspermia – cite_note-4 Kelvin (1871), Hermann von Helmholtz (1879) and, somewhat later, by Svante Arrhenius (1903). Much to the surprise of most people even Charles Darwin was a proponent.

Panspermia is not meant to address how life began, just the propagation method that may cause its sustenance.
http://profchandra.org/panspermia-3/