We're just starting an energetic space exploration with appearance of better tools in the recent years. Getting to the Moon is relatively easy, and could be barely done with much more modest technology; now we plan a bigger scale program. Getting people to Mars is undoubtedly more complex, but still within reach of the existing - or almost existing - technology. Getting furter from Earth, while not immediately in the plans, may get just as possible and useful with time, and we shouldn't claim to know what could be our reasons tomorrow to visit, say, Ceres or Venus. There is no scientific impossibility for flying almist anywhere in Solar system - the matter is only in needs and economic costs. Our predecessors could be confused with our habits of flying between continents and islands the way we can and do today - similarly some of us may not see the immediate reason to leave Earth - that can pass, as past habits got changed to our current ones.