据估计,外空间物质每年降落到地球表面有几千到几百万吨。已收集到的陨石个体大的可达数十吨如西南非霍巴(Hoba)铁陨石,小至微粒。这些来自外空间的物质我们通常称为陨石,但微粒一般称为宇宙尘埃。陨石,在外空间大约以42公里/秒的速度沿椭圆轨道绕太阳运行。一旦它运行进入地球轨道,尾随着以30公里/秒速度环绕太阳转的地球并追上它,这时陨石体就以12公 It is estimated that outer space material landed on the earth’s surface every year from a few thousand to several million tons. Meteorites have been collected up to tens of tons of individual large as South Africa, Hoba iron meteorites, as small particles. These materials from the outer space, which we commonly refer to as meteorites, but the particles are generally called cosmic dust. Meteorites, in the outer space about 42 km / s orbit the sun along the elliptical orbit. Once it runs into Earth’s orbit, trailing the Earth that revolves around the sun at a speed of 30 km / sec and catching it, the meteorite body at 12 km