The Chemistry of Life: Why Phosphorus and Nitrogen Rule the Stars

The implications for our search for aliens are somewhat sobering. By applying these chemical constraints to our current models, researchers estimate that the number of truly habitable planets might be significantly lower than previously thought—perhaps only 1% to 10% of earlier estimates. If this is true, the "Great Silence" of the universe (the Fermi Paradox) might be explained by the fact that while water is common, the precise chemical conditions required to kickstart life are exceedingly rare, making biological worlds few and far between.