土卫一：有大坑的小卫星
(原标题: Mimas: Small Moon with a Big Crater)
2025-01-12
浏览次数: 17
撞击土卫一的东西几乎摧毁了它。留下的是土星最小的圆形卫星上最大的撞击坑之一。分析表明，稍微大一点的撞击可能会彻底摧毁土卫一。这个巨大的陨石坑，以1789年发现土卫一的威廉·赫歇尔爵士的名字命名为赫歇尔，跨度约130公里，如图所示。土卫一的低质量使其表面引力强到足以形成一个球形物体，但又弱到足以形成如此大的表面特征。土卫一主要由水冰和少量岩石组成，所以它被准确地描述为一个又大又脏的雪球。这张特色图片是在2010年卡西尼号机器人飞船在土星轨道上飞过土卫一时拍摄的。互动：1月14日：纽约业余天文学家协会主办的变焦APOD讲座
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Whatever hit Mimas nearly destroyed it. What remains is one of the largest impact craters on one of Saturn's smallest round moons. Analysis indicates that a slightly larger impact would have destroyed Mimas entirely. The huge crater, named Herschel after the 1789 discoverer of Mimas, Sir William Herschel, spans about 130 kilometers and is featured here. Mimas' low mass produces a surface gravity just strong enough to create a spherical body but weak enough to allow such relatively large surface features. Mimas is made of mostly water ice with a smattering of rock - so it is accurately described as a big dirty snowball. The featured image was taken during the closest-ever flyby of the robot spacecraft Cassini past Mimas in 2010 while in orbit around Saturn. Interactive: Take a trek across Mimas January 14: Zoom APOD Lecture hosted by the Amateur Astronomers of Association of New York