Mysterious “leopard spots” on a Martian rock could be evidence of extraterrestrial life—or of mere lifeless chemistry. Finding out the truth may require bringing the rock back to Earth

In a dry river valley on Mars, NASA’s Perseverance rover may at last have found its reason for being: evidence of ancient alien life—and with it, a lifeline for the space agency’s grand but troubled plan to bring Red Planet materials to Earth.

This potentially cosmos-quaking evidence may look like merely a humble rock, but it’s unlike any other seen before on Mars. Dubbed “Cheyava Falls” after a feature in Earth’s own Grand Canyon, the rock appears to be a coffee-table-sized, arrowhead-shaped outcropping of mudstone. But its most notable visual features are its reddish and whitish stripes—the former are speckled with dark-rimmed, light-colored splotches resembling a leopard’s spots. The red color likely comes from the iron mineral hematite, the Perseverance team says. The rover’s studies have revealed the whitish striations to be veins of water-deposited calcium sulfate, and they show that the dark rims of the curious “leopard spots” contain molecules of iron phosphate—a potential food for hungry subsurface microbes.