土卫八：绘制的3D卫星
(原标题: Saturn's Iapetus: Painted Moon in 3D)
2021-07-13
浏览次数: 40
土星的卫星土卫八发生了什么？这个奇怪的世界的大部分地区是深棕色的，而其他地区则是明亮的白色。这种暗物质的组成尚不清楚，但红外光谱表明它可能含有某种暗碳。土卫八还有一个不寻常的赤道脊，使它看起来像一个核桃。为了更好地了解这颗看似被涂上颜色的卫星，美国宇航局在2007年指示绕土星运行的卡西尼号宇宙飞船飞入土星2000公里以内。土卫八的3D照片。在南部看到的一个巨大的撞击坑跨度达450公里，似乎与一个类似大小的旧陨石坑重叠在一起。深色物质越来越多地覆盖在土卫八的最东端，使陨石坑和高地都变暗。仔细观察发现，这层黑色的涂层通常面向月球的赤道，厚度不到一米。一个主要的假设是，深色物质主要是相对温暖但脏的冰升华时留下的污垢。最初的一层黑色物质可能是由来自其他卫星的流星释放的碎片堆积而成的。
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What has happened to Saturn's moon Iapetus? Vast sections of this strange world are dark brown, while others are as bright white. The composition of the dark material is unknown, but infrared spectra indicate that it possibly contains some dark form of carbon. Iapetus also has an unusual equatorial ridge that makes it appear like a walnut. To help better understand this seemingly painted moon, NASA directed the robotic Cassini spacecraft orbiting Saturn to swoop within 2,000 kilometers in 2007. Iapetus is pictured here in 3D. A huge impact crater seen in the south spans a tremendous 450 kilometers and appears superposed on an older crater of similar size. The dark material is seen increasingly coating the easternmost part of Iapetus, darkening craters and highlands alike. Close inspection indicates that the dark coating typically faces the moon's equator and is less than a meter thick. A leading hypothesis is that the dark material is mostly dirt leftover when relatively warm but dirty ice sublimates. An initial coating of dark material may have been effectively painted on by the accretion of meteor-liberated debris from other moons.