Astrophysical and Biological Constraints on Radiopanspermia
  We have carried out a series of calculations involving bacteria and viruses embedded in dust grains, which are ejected from our solar system by radiation pressure, and travel through space to other star systems. Under many conditions, this kind of panspermia is impractical, primarily because the ultraviolet (UV) radiation of the present Sun inactivates the micro-organisms. However, if the organisms are shielded by an absorbing material like carbon, and if ejection takes place in the late-Sun (red-giant) phase of a one-solar-mass star like our Sun, there is a significant probability that these micro-organisms can reach another star system alive (i.e., with only sub-lethal damage from UV and ionizing radiation). In addition to panspermia with viable micro-organisms, we note that it is possible to seed the Galaxy with inactivated ones, whose DNA and RNA fragments may provide the initial information necessary to start biological evolution in favorable environments. 
Jeff Secker (Washington State University), Paul S. Wesson and James R.   Lepock (University of Waterloo)