Just to clarify
Some microbes may have already left Earth ages ago during
the massive bombardments that took place ages ago. They
may have caught rides on the debris kicked up from our planet
by impacting comets and planetoids. That was also the theory
behind the presumed "fossils" on several Mars meteorites.
So, somewhere, out there, descendants of Earth microbes may
be populating the galaxy even now as we speak, far across the
heavens....