I'm a big advocate of space travel. Partially because the entire earth is small as an atom compared to the vastness of space, but partially because the engineering required to live well in space often has implications for earthly living. Space is infinitely big (or nearly so), but travelers must live in tiny spaces with few resources, lest their air supply be sucked away by the vacuum.
Our little journey to the moon in the sixties gave us improved computers, TANG, improved radios, memory foam mattresses, and improved thrusters. We also got some technology that doesn't quite help as much on earth, like space suits. (People living on earth are highly unlikely to encounter high vacuum.) Though space suit technology may prove useful for improving, say, dialysis. (The space suit has to provide quite a lot of life support systems.)
So if we go forward with the proposal to visit Mars? We'll need to develop cramped quarters that still keep everyone alive for 3 straight months, up to six, we'll need medical support so that the astronauts' bones don't turn to mush along the way, we'll need to develop space farming, because otherwise the cargo burden is unbearable, We'll need to pack all this into a very tiny, low weight space. We'll also need all the instrumentation to do the experiments that make this financially worth while.
Medicine, materials science, and construction engineering would all gain a direct and major boost. And who knows what else might be discovered?