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Galileo gets slushy with Europa

点击量:   时间:2018-01-13 07:02:07

By Jeff Hecht Boston CLOSE-UP pictures of Europa have strengthened the theory that liquid water lies beneath the Jovian moon’s icy crust. The pictures, taken by the Galileo probe, show regions where slush rose through cracks in the ice. James Head, a geologist at Brown University in Providence, Rhode Island, believes this shows that Europa “is warm and active today”. Mike Belton of the National Optical Astronomy Observatories in Tucson, Arizona, the Galileo team leader, says the warmth comes from tidal heating by Jupiter’s gravity. No one knows what shattered the ice layer, which Belton thinks is a few kilometres thick. But he believes that once the cracks opened, warm, soft ice at the bottom of the sheet and warmer liquid water rose in a turbulent flow. It froze almost immediately at the surface, where the temperature is about −120 °C. One picture seems to show a 26-kilometre impact crater that filled with slush, leaving its interior the same height as the surrounding terrain. The date of the impact is unknown,