Millions, and maybe even billions of years from now, we have to leave Earth. Earth will be uninhabitable, and we need to look for a new home. That time should be now. We are already exploring the universe, looking for a new home. If we find a new planet that proves to be inhabitable, then we should also begin improving our rocket technology in order to help us reach our destination.
We need to explore a space and get to know of how universe was formed, how the universe works, if there are other planets or moons which could have a habitual life on which we could colonize them. And for that we need to find more data regarding our galaxy. So I think exploring the space is absolutely worth it.
Of course we should explore space! It is a human's natural instinct to gather knowledge, to explore the unknown. How else would we have progressed so far as a planet? Denying this natural instinct, our race's thirst for knowledge, would simply be frustrating, with some negative affects. Let's continue exploring space!
If you look at all the resources including time, money, lives, and materials, it adds up to a staggering amount. What did we get from this investment? Moon rocks. Thing is, WE didn't really get them. The government did. Even tho we paid for them, they are not ours. About the only ways we can even get close to them is if we either work for the government in a research field or if we pay admission to a place that exhibits a few of them. Basically, we got NOTHING. About the only thing we get from space exploration is information. Information about places that we will/should never go. For this, all we really need is an unmanned space probe. At the rate technology is already advancing, we can make them even better than prior ones. By sending out more advanced probes, we can get the same information at a fraction of the price and not risk human lives in the process.