Making Sense of the Chemistry That Led to Life on Earth

Nicholas Wade in The New York Times:

Origins-600It was the actions of Jupiter and Saturn that quite inadvertently created life on Earth — not the gods of the Roman pantheon, but the giant planets, which once orbited much closer to the sun. Driven outward, they let loose a cascade of asteroids, known as the Late Heavy Bombardment, that blasted the surface of the young Earth and created the deep pockmarks still visible on the face of the moon. In the heat of these impacts, carbon from the meteorites reacted with nitrogen in Earth’s atmosphere to form hydrogen cyanide. Though a deadly poison, cyanide is nonetheless the ancient pathway for inert carbon atoms to enter the chemistry of life.

By the time the Late Heavy Bombardment had eased, some 3.8 billion years ago, the cyanide had rained down into pools, reacted with metals, evaporated, been baked and irradiated with ultraviolet light, and dissolved by streams flowing down to a freshwater pool. The chemicals formed from the interactions of cyanide combined there in various ways to generate the precursors of lipids, nucleotides and amino acids. These are the three significant components of a living cell — lipids make the walls of a cell’s various compartments; nucleotides store its information; and amino acids assemble into the proteins that control its metabolism. All of this is a hypothesis, proposed by John Sutherland, a chemist at the University of Cambridge in England. But he has tested all the required chemical reactions in a laboratory and developed evidence that they are plausible under the conditions expected of primitive Earth. Having figured out a likely chemistry needed to produce the starting materials of life, Dr. Sutherland then developed this geological scenario because it provides the conditions required by the chemistry. As for the chemistry itself, that springs from Dr. Sutherland’s discovery six years ago of the key to the RNA world.

More here.