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,…

陨石坑农场

陨石坑农场

ByNASA中文

影像来源：NASA/JPL 在一张名为“陨石坑农场”的麦哲伦图片中，我们看到了火山活动和撞击坑的奇特分层。 这张金星表面的三维透视图显示了三个撞击坑。图像的中心位于拉维尼亚平原西北部，大约南纬27度，东经339度。 科学家/工程师对这张图片的看法： “我记得当我第一次看到麦哲伦任务初期的新闻稿图片时，该地区被非正式地称为’陨石坑农场’。我可以从那张照片中看到金星有一些很奇怪的地方。即使这张照片是90年代初拍摄，但是现在看起来还是很奇怪。陨石坑农场的图像显示了这些看起来非常原始的陨石坑，它们叠加在火山背景上，完全没有覆盖到陨石坑的边缘。 至少在这张照片中，当金星被陨石坑覆盖时，所有这些发光的火山活动不知何故停止了。当然，这不应该是一个合理的行星历史；火山活动应该停止，陨石坑应该继续存在——除非这个星球有一段奇怪的历史。我记得看着这张照片，我想这里发生了一些奇怪的事情，它对地金星整个历史、气候、大气和地质都有重要的影响。我仍然认为这是对的。金星成了我职业生涯中的一个重要组成部分——找出照片中金星的奇怪之处。” ——大卫·格林斯彭：丹佛自然与科学博物馆天体生物学馆长

黎明时分的第谷与克拉维乌斯环形山

黎明时分的第谷与克拉维乌斯环形山

ByNASA中文

2022年7月16日 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…

火卫一：注定灭亡的卫星

火卫一：注定灭亡的卫星

ByNASA中文

2022年7月3日 Phobos: Doomed Moon of Mars Image Credit: HiRISE, MRO, LPL (U. Arizona), NASA Explanation: This moon is doomed. Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic. These martian moons may well be captured asteroids originating in the main asteroid belt between Mars and Jupiter or perhaps from even more distant reaches of our Solar System. The larger moon, Phobos, is indeed seen to be a cratered, asteroid-like object in this stunning color image from the robotic Mars Reconnaissance Orbiter, with objects as small as 10 meters visible. But Phobos orbits so close to Mars – about 5,800 kilometers above the surface compared to…

贝比科隆博号太掠过水星

贝比科隆博号太掠过水星

ByNASA中文

2022年6月28日 Mercury from Passing BepiColombo Image Credit & License: ESA, JAXA, BepiColombo, MTM Explanation: Which part of the Moon is this? No part — because this is the planet Mercury. Mercury’s old surface is heavily cratered like that of Earth’s Moon. Mercury, while only slightly larger than Luna, is much denser and more massive than any Solar System moon because it is made mostly of iron. In fact, our Earth is the only planet more dense. Because Mercury rotates exactly three times for every two orbits around the Sun, and because Mercury’s orbit is so elliptical, visitors on Mercury could see the Sun rise, stop in the sky, go back toward the rising horizon, stop again, and then set quickly over the other horizon. From…

第谷与克拉维乌斯环形山

第谷与克拉维乌斯环形山

ByNASA中文

2021年8月5日 Tycho and Clavius Image Credit & Copyright: Eduardo Schaberger Poupeau Explanation: South is up in this detailed telescopic view across the Moon’s rugged southern highlands. Captured on July 20, the lunar landscape features the Moon’s young and old, the large craters Tycho and Clavius. About 100 million years young, Tycho is the sharp-walled 85 kilometer diameter crater near center, its 2 kilometer tall central peak in bright sunlight and dark shadow. Debris ejected during the impact that created Tycho still make it the stand out lunar crater when the Moon is near full, producing a highly visible radiating system of light streaks, bright rays that extend across much of the lunar near side. In fact, some of the material collected at the Apollo 17…

梅西耶陨石坑的立体影像

梅西耶陨石坑的立体影像

ByNASA中文

2020年12月11日 Messier Craters in Stereo Image Credit: Apollo 11, NASA; Stereo Image Copyright Patrick Vantuyne Explanation: Many bright nebulae and star clusters in planet Earth’s sky are associated with the name of astronomer Charles Messier from his famous 18th century catalog. His name is also given to these two large and remarkable craters on the Moon. Standouts in the dark, smooth lunar Sea of Fertility or Mare Fecunditatis, Messier (left) and Messier A have dimensions of 15 by 8 and 16 by 11 kilometers respectively. Their elongated shapes are explained by the extremely shallow-angle trajectory followed by an impactor, moving left to right, that gouged out the craters. The shallow impact also resulted in two bright rays of material extending along the surface to the…

毅力号着陆点：杰泽罗陨石坑

毅力号着陆点：杰泽罗陨石坑

ByNASA中文

Credit: NASA/JPL-Caltech/ASU 这张俯视图由轨道上拍摄的NASA图片制成，蓝色圆圈表示的是火星车将要着陆的区域，图片中心的弧形山丘高约1600英尺，是杰泽罗陨石坑（Jezero Crater）的边缘部分。 Credit：NASA JPL 火星2020（Mars 2020）的任务目标是了解火星上是否曾经存在过生命。如今的火星表面太冷也太干燥，生命无法生存，但在数十亿年前杰泽罗陨石坑形成之后，它就注满了水，形成了一个与太浩湖（Lake Tahoe）差不多大小的深湖。随着火星的气候变化，杰泽罗湖最终完全干涸，火星表面的水也消失了。 古老的湖泊是我们寻找可能火星生命的理想之地，在地球上，湖泊里满载着鲜活的生命，通常而言，生命存在的证据留藏在沉积于湖底的泥沙中。正因如此，我们用火星车上的仪器对古代湖床的岩石进行探索，在这里，我们能探寻到早期湖泊的证据。 河流的蚀刻留下了一道峡谷划破陨石坑边缘，当水流进湖中时，它放慢了流动的速度，沉降了所携带的沙和泥，形成了扇形的三角洲。这里的白线是漫游车在最开始两年里可能的行进路径，也就是所谓的主要任务，在此期间，我们将使用火星车的科学仪器来分析湖泊沉积物。 在探索过三角洲之后，我们希望能探查早期湖泊的边岸线。为了到达那里，我们必须穿越如今火星上的沙丘之海。在这个角度，你可以看到从前的湖岸线在岬角周围弯折过来，甚至可以想象杰泽罗的湖水拍打在沙滩上的情形。最终，我们将行进到陨石坑的边缘。 杰泽罗陨石坑的形成源自一个大天体撞上了火星，掘出了火星地壳深处的岩石，袒露在陨石坑边缘让我们得以研究。撞击不久之后，这些岩石温度较高，可能曾孕育过温泉，这些泉水中的沉积物将是我们寻找火星上可能存在的古老生物的另一个目标。