Prebiotic Comet Collision Chemistry

The high temperatures and pressures generated by a comet hitting a planet could yield prebiotic molecules out of extraterrestrial ices carried by the comet, Nir Goldman of Lawrence Livermore National Laboratory revealed.

Goldman and colleagues modeled the shock compression and subsequent expansion of a typical comet mixture of water, methanol, ammonia, carbon monoxide, and carbon dioxide molecules to see what could happen if a comet were to smack into a planet's surface. For shock compressions lasting about 20 picoseconds at temperatures up to 4,000 K and pressures about 60 gigapascals, the researchers observed formation of chains of carbon and nitrogen atoms, some parts of which were akin to chains of amino acids.

When they modeled an expansion period of 50 picoseconds, the longer chains broke up into smaller components, including a glycine-CO₂ complex. The overall mixture is acidic, so the glycine-CO₂ complex could react with H₃O⁺ to produce glycine and CO₂ in an exothermic reaction, Goldman said.

The results show that a comet colliding with a planet could produce prebiotic chemicals from common interstellar building blocks, regardless of the planetary environment, he added.