This will really pay dividends in 5000 to 10000 years from now when we've f-up our planet to the point that humans have to migrate to another planet. By that time, the planet will somehow find a way to cleanse itself from the toxic residue caused by human waste, by the way of severe weather to the point we can't live in such conditions. i.e. massive flooding, ice age conditions, massive volcanic eruptions etc. that will cover the entire planet.
Besides, in a million years, the Andromeda galaxy will collide with our milky way galaxy. I think, Andromeda is coming towards us at a rate of 300,000 miles/hour.
So, if you give a crap about saving the human species in the wayyyyy future, then NASA is worth it. Just think about it, for every nickle the government is taking out of every paycheck you make, it's going towards saving your kid's kids' life, times it by10 years to the 10th power. It will give you something to watch as you're flying in heaven, or something for you to brew about, in hell.
Finally, it will keep the braniac kids from staying off the streets.