Astronomy Picture of the Day

Explanation: What's cooking on Io? This active moon of Jupiter is marked with volcanoes spewing lava that is now known to be hotter than any lava on Earth. Above is the highest resolution color-enhanced image yet composed of the most active surface in our Solar System. Features as small as three kilometers are visible. Sulfur compounds cause many of Io's unusual colors, while darker regions are probably composed of silicate rock.

木衛一的表面在忙些什麼？ 在木星活躍的衛星木衛一表面，火山不斷噴發出熔岩，而其熔岩比地球上任何已知的熔岩都要熾熱。 上圖是迄今呈現太陽系最活躍表面的最高分辨率彩色強化影像，在其中甚至可分辨出大小僅有三公里的小結構。 硫化物造就了木衛一的許多不尋常的顏色，而較暗區域的組成則可能是矽酸鹽。