In the velvet blackness of the outer Solar System, 400 million miles from the comfort of our own sun, lies a frozen world that may just be the most important address in our search for cosmic neighbours.
Jupiter's moon Europa has long teased astronomers with its vast, hidden ocean, a saline abyss containing more water than all of Earth's seas combined. But until now, a fundamental mystery remained: how could a world encased in a 20-mile-thick shell of ice ever hope to feed the life within?
