Finding oil on Mars won't make a bit of difference. The cost of sending it to earth is too cost preventative. Plus, we already have mega-trillions of tons of methane all over the solar system. We know right were it is and we aren't rushing to get it.
Simply put, we won't be doing much manned exploration of the solar system for about another 30 years and with good reason: getting shit off the earth is too expensive. It's a waste of time. Given the exponential increasing results of robotic explorers (intelligence and physical capabilities) and the general weaknesses of humans (food, air, disease, general frailty), our dollars would better be invested in robotic exploration. By 2025 our robots will have every basic capability humans do. Based on the current growth of computer technology, by 2020 we will be building laptops with more computational ability than a human brain. That's quite a leap.
So, then -- for now -- we can send robots further and cheaper than human flights and gain the same relative results. The net affect is: we get to visit more places because we don't have to spend lots of money on sending food, water, air and backup supplies in case of failure. A manned mission of Mars will cost on the order of half a trillion dollars and there are massive risks. Robotic mission to Mars do get more expensive, but that's because we are packing more into the rovers. But the costs are still pretty low: under $5 billion a pop. Within a decade the ESA, Russia, China, Brazil, India and Japan will also be sending probes all over the solar system. It's like that Japan, Brazil, Canada, USA, Australia and the ESA (and a few others) will begin unifying their investment capital into one program (it's already happening now). The net affect will be more advanced robotic missions, better results, more missions total.
Then, sometime around 2040 (or so) we may begin planning a manned mission. We'll have to wait until really strong nanotubes to build a fuel-saving space elevator. But by then, it will be just for ego as our robots will be delivering far more accurate, far more penetrating results than any manned mission could. They will -- after all -- be employing logical capabilities that outstrip any combination of human beings. By 2040 consider that a single laptop equivilent computer will have exabytes of storage, process in like base four (instead of binary) in 1 megabit chips at speeds exceeding exaflops. It will have every known contingency stored in his memory and be able to pre-calculate trillions of known possibilities before even landing. On being in whatever environment (say, the Oceans of Europa), it will be able to self repair and explore based on priorities that it discovers without any input from human beings.
~String