Imagine looking at earth from space. For the last few million years nothing happens, then in 1969, a small blip as a tiny spec leaves earth, touches the moon and then, blip, back again. This happens a few more times and then nothing.
People complain about costly things such as space exploration and high energy physics experiments. Why spend money on these things when we have issues like poverty?
This argument is nihilistic. Why do we build monuments, paint, make films, write music, when there is still poverty all around? There is enough food in the world; poverty is the result of politics, exploitation and war above all.
Human space exploration is one of our greatest achievements. To try and rationalize unmanned space flight on the grounds of practicality misses the point, it is like saying that the Sistine Chapel would be brighter if it were whitewashed.
As a byproduct, space exploration provides us with expensive toys that are not designed for killing each other. Remember this if you feel a slight pang of guilt at the instinctive curiosity of the sight of B2 bombers and stealth fighters on CNN in a few weeks.