在太空中还有一些资源是不能利用的,如彗星和流星体。彗星被称为“脏雪球”,因为它是由灰尘、冻结的气体和冰集结而成。彗星的速度极快,不是经常能遇到,因此不适宜做建设太空城的资源。 流星体不仅不可利用,而且是太空城的一种潜在危害。科学家们曾从地球上、月球上和太空中对流星体进行过大量的观测。他们发现,在太空中每平方千米面积上被一颗质量在1克以上的流星体穿过的可能性是每10年有1次,被100克以上的流星体穿 There are other resources that can not be used in space, such as comets and meteoroids. The comet is called a “dirty snowball” because it is made of dust, frozen gas and ice. Comets are extremely fast, not often encountered, and therefore unsuitable for building Space City resources. Meteoroid not only not available, but also a potential harm to the space city. Scientists have done a lot of observations of the meteoroids on Earth, on the moon and in space. They found that the possibility of passing a meteoroid of more than 1 gram mass per square kilometer of area in space was once every 10 years and exceeded by more than 100 grams of meteoroid wear