The coordinate of an organism on the Big Tree tells its relationship with any other organism on the Big Tree. The distance between listings is the difference between organisms. By counting the number of differences and similarities between genes of different organisms scientists can see how closely they are related. By taking samples of life and counting genetic traits, Dr. Pace and his colleagues can compare microbes to one another and determine similar traits. So this is the new habitable zone and you'll note again that it doesn't say anything about the distance from the sun.
Life exists everywhere on the surface of the Earth and below.
Microbial organisms are ubiquitous on Earth, not only the surface but also deep into the crust of the earth, and into the ocean, and into the sediments. I believe that if we ever get out there, if we ever find life in the solar system, I'm going to expect to find it rooted in The Big Tree. And the interesting question is not if it's related, but where is it grouped into the Big Tree. Dr. Norman Pace is Professor of Molecular, Cellular and Developmental Biology at the University of Colorado, Boulder. Pace is both a molecular biologist and a microbial ecologist.