They would be objects of outstanding size, a new family of giant comets or small planets, in a remote part of the solar system.
But they are assuming these micro-organisms came from a comet when no comet has been observed.
There have been several missions to comets over the past 20 years.
Once life has been seeded within a planet or comet it will grow at an exponential rate, checked only by the availability of sufficient nutrients.
He also wrote on the forecasting power of comets, again a topic where religious belief was, or could be, involved.
That might stimulate changes in organization that would make dealing with non-nuclear disasters, from comet-strikes and epidemics to catastrophic storms, easier.
It will rendezvous with the comet in 2014 and land a small probe on the surface.
It has become increasingly appreciated that, in addition to their cargo of ice and dust, comets also contain a large amount of organic material.