Many space probes have gone to various planets and other places in the Solar System to send back information. When people first went to space they didn't know what the effects of microgravity would have on humans so they sent animals instead. But in 1961 the Soviets launched the first human into space, Yuri Gagarin. The journey to planets is hazardous enough so that probably humans will not be used, and machines can pick up samples. Some people think that Mars can be mined for minerals which are rare and valuable. There are no plans at present to send humans to Mars.