July 28, 2011

The European Space Agency's (ESA) Herschel spacecraft has identified the source of water vapor ring surrounding Saturn. Enceladus, one of Saturn's moons, spews 550 pounds of water vapor into space every second. Anywhere from three to five percent of that water ends up falling onto the planet itself, influencing the chemical composition of its atmosphere. No other moon in the solar system is known to do that. The water expelled from Enceladus mostly erupts from jets in an area of the moon's south pole known as the "Tiger Strips" for their distinctive markings. Paul Hartogh, of the Max Planck Institute for Solar System Research, led the analysis of data gathered by Herschel and said the water emitted by Enceladus is "enough to explain the amount of water first discovered in Saturn's atmosphere" in 1997. According to Tilman Spohn, of the German Aerospace Center's Institute of Planetary Research in Berlin, the discovery is a puzzling one which gives rise to more questions than it answers. Enceladus' eruptions are surprising for a body of its size. A general assumption is that the larger a body in space is, the more unstable and active it becomes. Enceladus is too small to generate volcanic activity and heat. There is much more heat output than you would expect for a body like that. Yet beyond Enceladus' inexplicable qualities, the moon has caught scientists' interest in part because of the presence of liquid water which is a prerequisite for life as we know it. Enceladus seems to be covered by an ice cap with water underneath. An early explanation for the eruption of water could be Saturn's gravitational pull on its moon. Other moons of Saturn also have eruptions, although they spew materials other than water. Because of the low pressure in space, the water coming from Enceladus becomes vapor because can't remain in its liquid form or freeze. The water vapor is then broken down into hydrogen and oxygen by UV light and collisions with solar wind particles. Studying the conditions on Saturn and Enceladus can help scientists to understand what makes Earth so special in its ability to sustain life and explain how water came to Earth in the first place.