08年五大天文新发现 Top 5 Amazing Astronomy Discoveries in 2008
发布: 2008-12-28 11:41 | 作者: webmaster | 来源: 本站原创 | 查看: 260次
5. 揭开水星层层谜团
“信使”号探测器发回的水星照片
水星是太阳系中体积最小的行星——冥王星曾一度顶着这个头衔。但有关它的一切，还有一半以上仍旧是一个谜。2008年，天文学家最终揭开水星的层层神秘面纱。1月14日，宇航局的“信使”号探测器第一次飞越水星，开始为整颗星球拍摄的任务。迄今为止，“信使”号已经传回一系列令人着迷的水星图片，其中包括证明水星存在火山的图片。在“信使”号拍摄的卡勒里斯(Caloris)盆地图片中，我们能够看到存在熔岩流的线索以及一座体积超过美国特拉华州且斜坡比较平缓的盾状火山。
由于富含铁的地核慢慢冷却，现在的水星实际上正不断“萎缩”。根据“水手10”号拍摄的水星图片，科学家早在1974年便得出这一结论。与“水手10”号相比，我们在“信使”号所拍图片中看到更多断层。图片显示，水星收缩时产生的拉力在强度上至少比此前认为的高出三分之一。“信使”号拍摄的数千张图片以及获得的其它数据帮助科学家揭开水星的其它谜团，其中包括水星相对巨大的地核——构成这颗行星大约三分之二的质量。有观点认为，亿万年前的巨大撞击可能剥离了这颗处在太阳系最内部的行星最初的地表。
5. Solving Mercury mysteries
More than half of our solar system's smallest planet (Pluto once took this honor), Mercury, had remained a mystery until this year. On Jan. 14, NASA's MESSENGER probe made its first flyby of Mercury, beginning a mission to image the entire planet.
From the get-go, the probe sent back intriguing images, including clear evidence for volcanoes. Images of the Caloris basin showed hints of lava flows and the presence of a shield volcano larger than the state of Delaware, with gently sloping sides.
And Mercury is indeed shrinking as its iron-rich core slowly cools. Scientists had speculated this much from images taken during the Mariner 10 mission in 1974. But MESSENGER images showed more faults than did Mariner 10, suggesting the strain from the planet's contraction was at least one-third greater than originally thought.
More to come: The thousands of images and other data collected by MESSENGER could also shed light on other Mercury mysteries, including the planet's relatively giant core, which makes up about two-thirds of the planet's mass. One idea is that huge impacts hundreds of millions of years ago might have stripped the innermost planet of its original surface.
