黎明时分的第谷与克拉维乌斯环形山
Tycho and Clavius at Dawn
Image Credit & Copyright: Eduardo Schaberger Poupeau
Explanation: South is up in this dramatic telescopic view of the lunar terminator and the Moon’s rugged southern highlands. The lunar landscape was captured on July 7 with the moon at its first quarter phase. The Sun shines at a low angle from the right as dawn comes to the region’s young and old craters Tycho and Clavius. About 100 million years young, Tycho is the sharp-walled 85 kilometer diameter crater below and left of center. Its 2 kilometer tall central peak and far crater wall reflect bright sunlight, Its smooth floor lies in dark shadow. Debris ejected during the impact that created Tycho make it the stand out lunar crater when the Moon is near full though. They produce a highly visible radiating system of light streaks or rays that extend across much of the lunar near side. In fact, some of the material collected at the Apollo 17 landing site, about 2,000 kilometers away, likely originated from the Tycho impact. One of the oldest and largest craters on the Moon’s near side, 225 kilometer diameter Clavius is due south (above) of Tycho. Clavius crater’s own ray system resulting from its original impact event would have faded long ago. The old crater’s worn walls and smooth floor are now overlayed by newer smaller craters from impacts that occurred after Clavius was formed. Reaching above the older crater, tops of the newer crater walls reflect this dawn’s early light to create narrow shining arcs within a shadowed Clavius.
Tomorrow’s picture: Europa and Jupiter
黎明时分的第谷与克拉维乌斯环形山
影像提供与版权: Eduardo Schaberger Poupeau
说明: 在这幅月亮明暗界线及崎岖南方高原的精采望远镜影像里，上方是南方。在7月7日拍摄这片月面景观之时，月相为上弦月。影像中，随着黎明降临此区年轻的第谷坑及古老的克拉维乌斯坑，阳光以低角度从右侧入射。稚龄约1亿年的第谷坑，是影像中左下方有尖耸坑墙、宽85公里的环形山；它2公里高的中心峰和远侧的坑墙，沐浴在明亮的阳光中，而其坑底则则隐没在暗影里。在月亮接近满相的期间，产生第谷坑的撞击喷溅出之碎片，所形成的明亮辐线系统清楚可辨，并遍及大半的月球正面，更让它成为月面最吸睛的环形山。事实上，虽然阿波罗17号的著陆点远在2,000公里之外，但集自该处的月面物质，可能是源自造就第谷坑的撞击事件。第谷坑南侧（上方）、225公里宽的克拉维乌斯坑，是月球正面最古老最大的环形山之一。不过，造成克拉维乌斯坑的撞击所产生之辐线系统，在很久以前即已消褪不再可见。这个古老撞击坑的消蚀坑墙及平滑坑底，上头叠着克拉维乌斯坑形成之后，陆续发生的撞击所产生的小环形山。而耸出于这个老环形山的较新撞击坑之坑墙，顶部反射黎明的阳光，产生了克拉维乌斯坑暗影里的狭窄明亮光弧。
明日的图片: Europa and Jupiter
