I'm a sucker for big picture writing, and Dimitar Sasselov does that in the March issue of SEED, describing a second "Copernican" revolution. But instead of playing up the insignificance of our place in the universe, this leap in knowing will emerge from the importance of life in the history of the universe. After all, animate matter has been around for billions of years on Earth, a significant length of time in the 13.7 year history of the universe as a whole.
In the big picture, the problem is that given the lack of alternate examples, a definition of life has been notoriously hard to pin down. So we settle for descriptives of the process of living: living things grow, respond to stimuli, reproduce and so on. As Sasselov suggests, exoplanetology, a field of study that is itself only 15 years old, might offer tantalizing clues about what life is - as oppose what it does - the different kinds of conditions under which it might arise, and the alternate chemistries that, in fact, precede biologies.
Compared to the diversity of possible planetary systems suggested by theoretical models, our own solar system appears to offer a very limited set of planetary geochemical environments for us to sample. Astronomers are now rapidly discovering entirely new classes of planets orbiting other stars. One kind in particular—rocky planets with two to 10 times the mass of Earth—is turning up seemingly everywhere we look. These so-called “super-Earths” probably have characteristics quite different from our own planet, but they may very well be cradles for forms of life with exotic biochemistries. Across the light-years, we may soon study these bizarre planets for global signs of life. These studies will inform our efforts in the lab, and vice versa, in a self-reinforcing process that leads towards understanding the cosmic conditions for life.
By studying those worlds directly over the next few decades, Sasselov suggests a revolution even more grand than the material and technical revolution sparked by Copernicus' discovery that the Earth revolved around the sun, not vice versa. Armed with the knowledge of alternate and biologically prone chemistries, we could be on the verge of a synthesis in biology over the coming decades, a more than worthy successor to the 20th century revolution in chemistry. It's a startling idea.