土卫七: 有古老陨石坑的卫星

土卫七: 有古老陨石坑的卫星

ByNASA中文

2023年3月12日 Saturn’s Hyperion: A Moon with Odd Craters Image Credit: NASA, ESA, JPL, SSI, Cassini Imaging Team Explanation: What lies at the bottom of Hyperion’s strange craters? To help find out, the robot Cassini spacecraft that once orbited Saturn swooped past the sponge-textured moon and took images of unprecedented detail. A six-image mosaic from the 2005 pass, featured here in scientifically assigned colors, shows a remarkable world strewn with strange craters and an odd, sponge-like surface. At the bottom of most craters lies some type of unknown dark reddish material. This material appears similar to that covering part of another of Saturn’s moons, Iapetus, and might sink into the ice moon as it better absorbs warming sunlight. Hyperion is about 250 kilometers across, rotates chaotically,…

土卫八: 有怪异表面的卫星

土卫八: 有怪异表面的卫星

ByNASA中文

2023年2月26日 Saturn’s Iapetus: Moon with a Strange Surface Image Credit: NASA, ESA, JPL, SSI, Cassini Imaging Team Explanation: What would make a moon look like a walnut? A strange ridge that circles Saturn’s moon Iapetus’s equator, visible near the bottom of the featured image, makes it appear similar to a popular edible nut. The origin of the ridge remains unknown, though, with hypotheses including ice that welled up from below, a ring that crashed down from above, and structure left over from its formation perhaps 100 million years ago. Also strange is that about half of Iapetus is so dark that it can nearly disappear when viewed from Earth, while the rest is, reflectively, quite bright. Observations show that the degree of darkness of the…

被土星反照光照亮的土卫二

被土星反照光照亮的土卫二

ByNASA中文

2023年2月5日 Enceladus by Saturnshine Image Credit: NASA; ESA, JPL, Cassini Imaging Team, SSI; Color Composite: Gordan Ugarkovic Explanation: This moon is shining by the light of its planet. Specifically, a large portion of Enceladus pictured here is illuminated primarily by sunlight first reflected from the planet Saturn. The result is that the normally snow-white moon appears in the gold color of Saturn’s cloud tops. As most of the illumination comes from the image left, a labyrinth of ridges throws notable shadows just to the right of the image center, while the kilometer-deep canyon Labtayt Sulci is visible just below. The bright thin crescent on the far right is the only part of Enceladus directly lit by the Sun. The featured image was taken in 2011…

卡西尼号从土星往外看

卡西尼号从土星往外看

ByNASA中文

2022年12月23日 Cassini Looks Out from Saturn Image Credit: NASA, JPL-Caltech, Space Science Institute Explanation: This is what Saturn looks like from inside the rings. In 2017, for the first time, NASA directed the Cassini spacecraft to swoop between Saturn and its rings. During the dive, the robotic spacecraft took hundreds of images showing unprecedented detail for structures in Saturn’s atmosphere. Looking back out, however, the spacecraft was also able to capture impressive vistas. In the featured image, taken a few hours before closest approach, Saturn’s unusual northern hexagon is seen surrounding the North Pole. Saturn’s B ring is the closest visible, while the dark Cassini Division separates B from the outer A. A close inspection will find the two small moons that shepherd the F-ring,…

土星的夜面

土星的夜面

ByNASA中文

2022年11月26日 Saturn at Night NASA, JPL-Caltech, Space Science Institute, Mindaugas Macijauskas Explanation: Saturn is still bright in planet Earth’s night skies. Telescopic views of the distant gas giant and its beautiful rings often make it a star at star parties. But this stunning view of Saturn’s rings and night side just isn’t possible from telescopes closer to the Sun than the outer planet. They can only bring Saturn’s day into view. In fact, this image of Saturn’s slender sunlit crescent with night’s shadow cast across its broad and complex ring system was captured by the Cassini spacecraft. A robot spacecraft from planet Earth, Cassini called Saturn orbit home for 13 years before it was directed to dive into the atmosphere of the gas giant on…