Enceladus is a moon of Saturn that was discovered in 1789 by the British astronomer Sir William Herschel (1738-1822). This relatively small moon has a diameter of approximately 310 miles (500 km) and orbits around Saturn at a distance of 147,898 miles (238,020 km) with a period of rotation of 1.37 days. The surface of Enceladus is dominated by fresh, clean ice, giving the moon an albedo of almost one. Because Enceladus reflects almost 100 percent of the incident sunlight, the moon has a surface temperature of only -330°F (-201°C). Since early 2005, the Cassini spacecraft has uncovered many mysteries about this intrigu ing moon. The Cassini spacecraft's magnetometer discovered an atmosphere around Enceladus, providing scientists evidence that gases may be escaping from the moon's surface or interior. In November 2005, the Cassini spacecraft's visual and infrared mapping spectrometer measured the spectrum of plumes originating from the south pole of the icy moon, providing scientists a very clear signature of small ice particles. Images of plumes of icy materials streaming from Enceladus's south pole, suggest that the moon has Yellowstone Park-like geysers fed by near-surface reservoirs of liquid water.
the evidence is direct observation (by instruments on board the Cassini spacecraft) of water vapor venting from liquid-water sources close to the surface. Scientists will be given another close-up look at Enceladus in the spring of 2008 when the Cassini spacecraft is scheduled to fly past this intriguing moon within 220 miles (350 km) of its surface.
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