Prize: NASA could offer a prize—say $3 billion to the first company and $1 billion to a second company—for delivering something like 1 kg of Mars rocks and soil back to Earth. NASA has used prizes very sparingly in the past, but this option could appeal to the Trump administration as it would require very little funding up front.

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.