从太空俯视马尼夸根陨石坑
影像来源与版权:NASA, International Space Station Expedition 59

说明:4月11日,在地球加拿大魁北克省上空400公里高轨道上飞行的国际太空站第59探险队组员,拍下了这张宽广罗伦斯河及令人好奇的马尼夸根环形湖之影像。在影像中右方的环形湖,是一座位在100公里直径,受到高度侵蚀的古老撞击坑遗迹之内的现代水库。这个古撞击坑,除了是在轨道上清楚可见的结构之外,更可提醒我们地球是多么容易受到太空岩石的影响。高龄超过二亿年的马尼夸根陨石坑,可能是由一颗直径大约5公里的石质天体造成的。据目前所知,在下个100年之中,并没有任何已知的小行星具有严重威胁地球的机率。不过,目前正在举行的2019年国际宇航学院行星防卫研讨会,提出了一个虚构的事件,以作为小行星撞地球对策练习。(Manicouagan crater 马尼夸根陨石坑)
翻译:“每日一天文图”成大物理分站

Manicouagan Impact Crater from Space
Image Credit & Copyright: NASA, International Space Station Expedition 59

Explanation: Orbiting 400 kilometers above Quebec, Canada, planet Earth, the International Space Station Expedition 59 crew captured this snapshot of the broad St. Lawrence River and curiously circular Lake Manicouagan on April 11. Right of center, the ring-shaped lake is a modern reservoir within the eroded remnant of an ancient 100 kilometer diameter impact crater. The ancient crater is very conspicuous from orbit, a visible reminder that Earth is vulnerable to rocks from space. Over 200 million years old, the Manicouagan crater was likely caused by the impact of a rocky body about 5 kilometers in diameter. Currently, there is no known asteroid with a significant probability of impacting Earth in the next century. But a fictional scenario to help practice for an asteroid impact is on going at the 2019 IAA Planetary Defense Conference.
Astronomy Picture of the Day 05/02/2019