I just came across this CNN article about evidence of recent water activity on Mars. It seems that images taken over time by the now lost Mars Global Surveyor show new gullies that seem to have been dug on Mars, possibly by water. Here is a link to the official NASA images. This opens up all kinds of possibilities. Mars could still be volcanically active. There could be the precursors of life or even life itself on Mars. They will probably try to be even more careful to sterilize the next Mars explorer before it is launched. This news makes it imperative to start work on a serious effort to send a manned mission to Mars. It will take a long time to get going.
About 12 years ago I started reading the Mars series: Red Mars, Green Mars, and Blue Mars by Kim Stanley Robinson. The trilogy described how Mars could be colonized with existing technology. The first book was the best. The last two were good, although they required some interesting conjectures of earthly political and environmental developments.
Water on Mars. It's amazing.