Scientists are narrowing down explanations for a potential chemical sign of ancient life on Mars. This sign – marks found on Martian rocks last year – could have been caused by microbes or by a reaction that takes place only at high temperatures. New findings suggest the biological explanation is more likely.

Last year, while exploring an ancient lakebed called Bright Angel in Mars’s Jezero crater, NASA’s Perseverance rover discovered a rock with unusual markings – called “leopard…