首页>英语角 > 听力 > 美音 > 课 程 > 科学 > 高三>All About Mercury
All About Mercury
Question
Mercury goes around the Sun once every 88 days in a very
提交
Its speed across the sky prompted the ancient Greeks to name it Mercury after the Greek messenger to the Gods. He is usually depicted wearing a winged hat and winged shoes.Mercury is the closest planet to the Sun. It is also the smallest planet in the solar system, it is not much bigger than our Moon.Mercury goes around the Sun once every 88 days in a very elliptical orbit. At its closest to the Sun it is 46 million km but at its furthest point it is 70 million km.Being this close to the Sun, the temperature on the surface can be as high as 430°C on the sunlit side to -180°C on the dark side.(-292 to +806°F).Although a year on Mercury lasts for 88 days, it rotates very slowly and so one day on mercury lasts for 58 days! It would be a very strange sight to see the Sun moving so slowly during a Mercurian day. Because it is so close to the Sun it is very difficult to see from Earth as it is only visible for a few short days when it is at its most extreme to the left or right of the Sun. Then, shortly after sunset or just before sunrise it can be seen as a bright, pink coloured star.Through a telescope we see it as a changing crescent shape, going through phases similar to the Moon.On rare occasions Mercury crosses in front of the Sun in what we call a ‘transit of Mercury'. The tiny black disc can be seen against the face of the Sun.Almost everything we know about Mercury comes from a NASA probe, “Mariner 10” which flew past Mercury three times between 1974 and 75. It sent back amazing close up pictures.Mariner 10 told us that the surface of Mercury is very similar to the Moon. It is heavily cratered after millions of years of bombardment from meteorites.The south pole, high mountain ranges and long rivers of once molten lava can be seen snaking across the surface.While Mercury may be the smallest planet it is also one of the heaviest, as it made of 70% iron. With a core made of liquid molten Iron and a very thin surface crust.Mercury has a very thin atmosphere but any water that may have ever been there has long been boiled away.A new probe, “Messenger” was launched by NASA in 2004 and will rendezvous with Mercury in 2011 after passing by Venus. It is very unlikely that a probe will land on Mercury in the near future, it is simply too hot.
视频文本已隐藏,本文本来自网络或网友仅供参考
显示视频文本

Discuss

0 comments
characters remainingSubmit
反馈