Or, according to NASA, it used to be. The Mars rovers have found conclusive evidence that the area in which they are poking around was covered with "liquid water" (stupid question: is there any other kind?) at one time. The scientists still have a lot of research ahead of them to explain when the water existed and why it disappeared. But just the fact that they can tell it was there at all is a big discovery.
As cool as this discovery – and the pictures sent back by the rovers – are, I’m still not sold on manned missions to the planet. We seem to be getting a lot of science for the money out of these two little golf carts. Congratulations to the folks at NASA and JPL!