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火星是大家都很感兴趣的一个星球,它和地球有许多相似的地方。火星自轉的速度差不多和地球相等,它的自轉轴是倾斜的,倾斜度也和地球差不多,这就是說火星与地球一样,一年有四季的分別。但是火星也有和地球不同的地方,它比地球小,直径只有地球的一半;火星上也有空气,但是很稀薄,空气的压力只有地球上的二十分之一。因此在这个星球上引力是很小的,只有地球的二分之一:对運动着的物体說来,空气的阻力也比地球小
Mars is a planet that everyone is interested in. It has many similarities with Earth. Mars rotates at almost the same speed as the Earth. Its axis of rotation is tilted, and its inclination is similar to that of the Earth. This means that Mars, like Earth, has a difference of four seasons a year. But Mars also has a place different from Earth. It is smaller than Earth and only has half the diameter of Earth. Mars also has air, but it is thin, and the pressure of air is only one-twentieth of that on Earth. Therefore, the gravitation on the planet is very small, only half of the earth: for the moving object, the resistance of the air is smaller than that of the earth.