Comets colliding with Earth could have been the key to forming life-producing complex chemicals out of simple building blocks, according to computational work by Nir Goldman of Lawrence Livermore National Laboratory and Isaac Tamblyn of the University of Ontario Institute of Technology (J. Phys. Chem. A 2013, DOI: 10.1021/jp402976n). The duo looked at what happened to a mixture of simple cometary chemicals—H2O, CO, CO2, CH3OH, and NH3—when it is exposed to a brief high-temperature and high-pressure environment similar to a comet impact. They simulated up to a 260-picosecond sequence of shock compression followed by expansion and cooling to equilibrium in ambient conditions. The study expands on previous work by Goldman and colleagues that simulated a shorter time period. Goldman and Tamblyn found that shock compression yields C–C and C–N bonded networks that are highly reactive and have short lifetimes. Expansion and cooling then produces possible prebiotic species such as aromatic compounds and amino acid precursors, depending on the collision shock conditions.