剑砍在石地上，火星飞溅。
继任的系统同样是设计用来2020年重返月球的，同时作为远征火星的踏脚石。
That successor system is also designed to return humans to the moon by 2020, as a stepping stone to visiting Mars.
把人类送上火星进行探测的一种方法，是在月球上建立一个基地，用来作踏脚石。
One way for human missions to Mars is to set up a base on the moon to be used as a steeping-stone.
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