Three and a half billion years ago, waves splashed and streams surged across this dusty expanse on Mars now known as Jezero Crater. On a nascent Earth, chemistry was coagulating toward the exalted state we call life.
Astronomers, philosophers and science fiction writers have long wondered whether nature ran the same experiment there as on Earth. Was Mars another test tube for Darwinian evolution? No longer will you be laughed out of biology class for speculating that life actually evolved on Mars first and drifted to Earth on a meteorite, or that both planets were seeded with microbes or proto-life from somewhere even farther way.
So humans have sent their progeny across time and 300 million miles of space in search of long-lost relatives, ancient roots of a family tree that might be traced in the Red Planet’s soil.