Geyser teaser

摘要

Far from the warmth of the sun, in a frigid realm of the solar system a billion kilometres beyond Earth, lies a ball of ice called Enceladus. Only 500 kilometres across, it is one of many icy little moons in orbit around Saturn. They are all geologically dead, their ancient cratered surfaces unchanged in aeons - except for Enceladus.rnThe surface of Enceladus is fresh and new, and the palest of any object in the solar system, reflecting about 90 per cent of the light that falls on it. When the Voyager 1 and 2 probes flew by in the early 1980s, they saw twisted canyons crossing its surface, and craters that seem slumped and softened. Then in 2005, NASA's Cassini spacecraft discovered that the south pole of Enceladus - a snowball's Antarctica - is actually far warmer than the rest of the moon. Most startlingly of all, geysers are erupting from the pole, sending vast plumes of vapour out into space.