I know Neil deGrasse Tyson would spank me silly for saying this, but I'm compelled to say it again (and again…): a manned mission to Mars would be inexcusably stupid and a monumental waste of resources.  

This is coming from an enormous nerd and sci-fi buff.  But I'm also an avid dilettante in physics and cosmology and have never seen anything in the science to suggest such a mission would ever be of any significant use to us, especially considering that the chances of us ever spreading out beyond the solar system are infinitesimal to nil.  

Also too, I cannot for the life of me ever get a direct and substantive answer to the question of "what potential benefit would justify the expense?"  No, getting America "dreaming" again is weak sauce, Neil.  And no, finding hints and whispers of life on another planet doesn't give me wood either.  

Sure, finding fossiled Martian trilobites would be super-sexy, take the media's mind off the 2032 presidential election for a couple of days and give lots of evangelicals a huge Sad (because maybe on Soviet Mars, dinosaur rides YOU), but – in my humble opinion – the dubious theoretical payoffs wouldn't be worth anywhere near the likely projected cost of more than ONE TRILLION DOLLARS by the time inflation and the inevitable waste, payoffs, fraud and overruns are factored in.  NASA itself estimated in 1989 that the total cost of sending a man to Mars would run in the neighborhood of $400 billion(ish) ($600 billion in today's dollars).

Notwithstanding all of that, the most egregious bullshit wrapped up in all of this is the fact that there is very little difference between the substantive operational capabilities of our ever-improving stable of Mars rovers and an earnest crew of unfortunate astronauts who we'd spit into space to endure nearly a year of interplanetary boredom on the U.S.S. Pointless.

So there you go.  /rant