I am a big proponent of space exploration and I wish we would spend a lot less on blowing people up and a lot more on finding out new science.
But I am not exectly sure I understand the implications behind this, or why it's such great news.
Basically, as I understand it, we've pretty much agreed that a lot of the land features on Mars were created by running water sometime in the past. So we know "there used to be liquid water on Mars".
Now we find more microscopic evidence showing that there was water, but it is not there where we are looking. So we instead of just knowing "there used to be liquid water on Mars" we now know "there used to be liquid water on Mars".
What am I missing? If the rover found actual liquid water, or ice crystals that could be harvested, I would see this as a fantastic discovery and welcome news for a future manned Mars mission. But that is not what they found. They found geologic evidence of liquid that isn't there now, but was there once. Which they already could infer from looking at the landscape evidence.
What am I missing? Why is this great news? Are they just happy that they have better proof that they were right all along?