February 28, 2011 | 1 Asteroids and comets have long been
suspected of helping nudge Earth toward life. The interplanetary
interlopers have struck Earth since the beginning, delivering
carbon, water, and sometimes organic compounds such as amino
acids. By providing key chemicals or even pre-formed biological
building blocks, as well as the heat and energy generated by a
meteorite impact, space rocks may have played an important role
in getting the biological ball rolling. A new paper in the
Proceedings of the National Academy of Sciences adds another
piece of evidence to back the idea that biological precursors
arrived aboard meteorites. In the study, published online
February 28, Sandra Pizzarello of Arizona State University and
her colleagues report that an Antarctic meteorite released
copious ammonia when heated with water. Ammonia provides a ready
source of nitrogen, which is a key ingredient in many
biomolecules, including DNA and the amino acids. Pizzarello and
her co-authors subjected a sample of the m