I learned by reading this thread that NASA is directly responsible for what budget it's assigned. Neat.
Mars is already littered with our defunct robots. The moon landing sites are littered with bags of urine, junked cars and torn up platforms ... not to mention a couple crashed probes.
For how cynical you are about humanity, you've got an absurdly anthropocentric idea of "littering". Humans have left a negligible amoung of waste on the moon, yes. To the universe, that's pretty irrelevant: a bit of inanimate matter on a huge chunk of inanimate matter, and nobody there to care about it one way or the other. To a civilization way more advanced than ours, these'd be some fascinating artefacts on an otherwise boring world. It takes a human to go "eww, astronaut poop".
Nothing less intelligent than us would know to be offended or bothered by anything humans have left on the moon, and to anything more intelligent than us, bitching about human artifacts on the moon would kinda be like finding a single feather, or speck of moss, on an otherwise lifeless rockface, and thinking the rockface forever ruined.
And this is what annoys me about people that run around bitching about how rubbish humanity is, often while wearing t-shirts reading "people=shit" and whatnot. It's not even that I disagree with the sentiment. It's that the people voicing it often seem to think they can disavow any connection to the unwashed masses of rubbish people simply by being sufficiently dickish. But in doing so, they will often end up exhibiting some of the worst human characteristics, with their dickishness often aimed at people exhibiting the best human characteristics - like the folks over at NASA in this case. If there's any single organization that's done more to expand our knowledge of the universe we live in over the last few decades than NASA, I'd really like to hear it.