A number of scientists reckon a more modest approach towards spreading life to other star systems might be possible. In the chill of deep space, bacteria somehow shielded from cosmic radiation might survive dormant for millions of years. Perhaps alien worlds could be seeded deliberately with terrestrial micro-organisms that might take hold there, jump-starting evolution on those planets.
There are many obstacles to directed panspermia, as this approach is known—and they are not just technical. Religiously minded critics claim “we’re playing God”, says Claudius Gros, a physicist at Goethe University in Frankfurt, who has floated the idea of scattering photosynthesising bacteria and algae on extrasolar planets. Critics argue in particular that “contaminating” other planets with terrestrial life in this way risks altering, or even destroying, any life that has arisen there independently. For support, they point to present-day concerns that bacteria carried by spacecraft might, if some form of life does exist there, do exactly that to Mars. This debate is hypothetical for now. But it will become more urgent if any of the projects currently being discussed to build probes to travel to nearby star systems gets off the drawing board and into space.