水星 (Mercury )，中国古代称为辰星。是太阳系中的类地行星，其主要由石质和铁质构成，密度较高。自转周期很长为58.65天，自转方向和公转方向相同，水星在88个地球日里就能绕太阳一周,平均速度47.89千米,是太阳系中运动最快的行星。无卫星环绕。它是八大行星中是最小的行星，也是离太阳最近的行星。水星在直径上小于木卫三和土卫六，水星上的太阳看上去要比在地球上大二倍半，太阳光比地球赤道的阳光还要强六倍。水星朝向太阳的一面，温度非常高，可达到400℃以上。这样热的地方，就连锡和铅都会熔化，何况水呢。 但背向太阳的一面，长期不见阳光，温度非常低，达到-173℃，在这里也不可能有液态的水。1974年3月、9月和1975年3月，美国发射的“水手10号”探测了水星，向地面发回5000多张照片。水星地貌酷似月球，大小不一的环形山，还有辐射纹、平原、裂谷、盆地等地形。水星是太阳系中仅次于地球，密度第二大的天体。

　　Ever wonder what it's like on other planets? On this Moment of Science, find out what it's like on Mercury.

　　The great astronomer(天文学家) Carl Sagan used to say that if he were transported anywhere in the solar system he would know which planet he was on just by looking around. In this spirit of knowing your neighborhood, here’s something we call . . . What’s It Like There?

　　Today we ask: What’s it like . . . on Mercury?

　　You’re standing at the equator(赤道) on Mercury just before sunrise. We’d better put you in a protective shelter, because it’s mighty(很，非常) cold–something around three hundred degrees below zero, Fahrenheit(华氏温度计的). That’s cold enough to freeze methane(甲烷，沼气).

　　But things are looking up–by midmorning(上午中段时间，上午十点左右) it should be a (1)balmy(温和的) eighty degrees outside. Of course, because of its rotation(自转) and orbit(公转), midmorning on Mercury comes twenty Earth days later, so you have a long wait.

　　When it finally arrives, though, you step outside in a protective suit and (2)bounce(跳) around in the low gravity. The ground is rocky and covered in craters(火山口). There’s no atmosphere at all, so the sky overhead(在头顶上) is black, even though the sun is perfectly visible.

　　In fact, the sun is far bigger, and brighter, than you’ve ever seen it on Earth–imagine a sun eleven times as bright! Not only that, the temperature is still climbing(上升的). By high noon it will be up to eight hundred degrees Fahrenheit, hot enough to melt zinc(锌). Clearly this is no place for humans.

　　Every Mercurial day, which lasts one hundred and seventy six Earth days, the planet undergoes the same unbelievable temperature fluctuation(温度波动) from super-cold to super-hot. Makes you glad to have a nice, temperate planet like Earth to come back to.

　　NOTES:

　　(1)balmy

　　adj. 芳香的;温和的;止痛的

　　1.A balmy breeze was blowing across the beautiful lake.

　　一阵柔和的微风轻吹过那美丽的湖面。

　　2.Love is balmy wind that soothes pain and anxiety from the tempests of the life.

　　爱是一丝温暖的微风，它能化解繁乱生活中梅花鹿焦虑和伤痛。

　　(2)bounce

　　n. 跳;弹力;活力

　　vt. 弹跳;使弹起

　　vi. 弹跳;弹起，反跳;弹回

　　1.The ball bounced off the wall and he caught it.

　　球从墙上弹回来，他接住了球。

　　2.Success is how high you bounce when you hit bottom.

　　成功就是在你落到底时你你能跳起多高。