no, not a joke at all. This site has some interesting info/links. [link] i've no idea if Mars is a 'hunk of rock and dirt', but it seems pretty obvious that Nasa used colour filters to obscure it, so it makes you wonder what else they obscure or hide.
I've seen what my friend does. She records the landforms on Mars. That's it. And she's seen enough to know that it's nothing more than what NASA says it is. As I said, she does not work for NASA, either.
The Brookings Report of 1951 specifically says that if ever they were to discoverer ETs then it should be kept from the public because the impact of such a discovery on human values, so yes they would or do hide that from the generalized public and anyone who does not have proper clearance to know about it. It being under the department of defense indicates it does have branches that are allowed top secret information. Things along the lines of weapons and new technologies that could be used as such are also under that umbrella as well as any alliances the government may or may not have with ETs or anything else beyond our world.