Unusual rocks discovered on Mars contain the most tantalising evidence yet of potential past life on the Red Planet.
The mudstones, found in a dusty riverbed by Nasa's Perseverance Rover, are dotted with intriguing markings nicknamed leopard spots and poppy seeds.
Scientists believe these features contain minerals produced by chemical reactions that could be associated with ancient Martian microbes.
It's possible the minerals were produced by natural geological processes, but the findings are significant enough to meet Nasa's criteria for what it calls "potential biosignatures".
This means that they warrant further investigation to determine whether they are biological in origin.
