I have been following all the various Mars missions since they started. Quite fascinating to say the least. The latest Curiosity mission is amazing. But, I have no doubt Mars was a viable planet in the distant past, until a devastating event occurred. Too many strange things have been photographed since the entire planet has been mapped by the latest camera technology. And, those are the photos that NASA lets us see and I have no doubt some have been altered.
Richard Hoagland has been involved quite deeply in all of this, and has some interesting facts and information, that if you choose to believe it or not, still raises questions. He has several videos on his website giving talks at various places. Worth a bit of time to hear what he has to say. Click on the Video Viewscreen and check out Curiosity's Stealth Mission.