Chris McKay

The search for another type of life in the solar system addresses the fundamental question of life in the universe. To determine if life forms we discover represent a second genesis, we must find biological material that would allow us to compare that life to the Earth's phylogenetic tree of life. An organism would be alien if, and only if, it did not link to our tree of life. In our solar system, the "worlds of interest" in our search for life are Mars, Europa, Enceladus, and, for biochemistry based on a liquid other than water, Titan.

If we find evidence for a second genesis of life we will certainly learn from the comparative study of the biochemistry, organismal biology, and ecology of the alien life. The discovery of alien life that is alive or revivable will pose fundamentally new questions in environmental ethics. We should plan our exploration strategy so that it is biologically reversible. In the long term we would do well, ethically and scientifically, to strive to support any alien life discovered as part of an overall commitment to enhancing the richness and diversity of life in the universe.