Comet impact may have prompted life on Earth

The impact of comets crashing into Earth's surface may have provided the energy to create molecules that formed the building blocks of life, scientists say.
The study was based on a computer model of such an impact's effect on a comet crystal initially made up of water, carbon dioxide and other simple molecules.
"Comets carry very simple molecules in them," said study co-author Nir Goldman, a physical chemist at Lawrence Livermore Laboratory in California.
"When a comet hits a planetary surface, for example, that impact can drive the synthesis of more complicated things that are prebiotic - they're life-building," Goldman said.

The notion that life-building molecules were carried to Earth via comets or asteroids, a hypothesis known as panspermia, has been around for decades.
But the idea that the comet impact itself could have created the molecules is newer, LiveScience reported.

When the Earth was young, comet bombardments may have brought 10 trillion kilogrammes of carbon-based material to the planet every year, Goldman said.
That would have provided a rich source for the building blocks of life to form.
Goldman and his colleagues used a computer model to simulate a single comet crystal of hundreds of molecules. Comets are mostly "dirty snowballs," Goldman said, so the simulated crystal started with mostly water molecules, but also included methanol, ammonia, carbon dioxide and carbon monoxide.

The researchers then simulated the effects of the crystal hitting the Earth's surface at various angles, from crashing into it directly to making a glancing blow.
They followed the chemical changes in the crystal for about 250 picoseconds, about the amount of time the system needed to reach a steady state, where the proportion and type of chemicals in the system is stable.
The huge jolt from the impact provided the energy needed to make complicated chemicals.
As a follow-up, Goldman and colleagues want to test different initial chemical concentrations in the comet to see how that affects the formation process.

The study was published in the Journal of Physical Chemistry A.