I was also wondering why the coinage sounded so generic when it seemed to imply the specificity of Mars

Check out my Fred Hoyle comment, guys. The "return" to Mars is actually the most recent version of the theory. Originally it was about viruses (? I think, rather than bacteria) travelling on comets, wandering all over the universe from who knows where. But possibly from clouds/nebulae of "dark" organic matter.

Seemed even more whacky than Erich von Daniken at the time.

Edit -
Here's some NASA stuff about how comets may have "seeded" the Earth with organic material:
http://science.nasa.gov/headlines/y2001/ast05apr_1.htm

And here's something about the recently-launched comet probe, and the relevance of its mission. "Essentially we can think of them as chemical fossils of processes that happened over four billion years ago when the Solar System was young and the planets were forming.":
http://news.bbc.co.uk/hi/english/sci/tech/newsid_2087000/2087291.stm