[WMarshal]

The ability of these microbes to survive dormancy for millennium makes the theory of meteors or comets seeding planets with life much more plausible.

Halley's Comet has an orbit that takes it from outside of Neptune's or it to inside of Earth's orbit every 75 years, well within the survivability of bacterial to lie dormant then coming to back to life when comet is in the inner solar system. Comets could be picking up and dispersing bacterial life throughout the solar system.

[MtnClimber]

I was thinking the same thing about meteors and comets.