Engineers have developed a new tool to help them hunt for signs of life on Mars. Their metre-long, white-hot spear can melt its way through soil and rocks to depths where evidence of past life may be lurking. If life ever existed on Mars, harsh conditions on the surface could mean the only remaining traces may be buried more than a kilometre down. But conventional drilling is unlikely to unearth them. “The soil is a mixture of sand, dust and rocks cemented together with salt minerals,” says John Bridges, who studies Martian geology at London’s Natural History Museum. “For the most part, it’ll be like digging in a sandpit.”