Curiosity landed about five months ago, and then began a long and sometimes agonizingly slow process of going through all of the mission's "first-time activities." They're still not done. There remains one more major task that Curiosity has to do for the first time: drill into a rock to acquire a powdered sample from its interior and deliver it to the Chemin and SAM instruments. Until they've successfully hurdled that obstacle, the engineers haven't yet really proven that the rover can do everything it was sent to Mars to do.

Now, the scientists knew that this process was going to take a while (though maybe not this long; it had originally been hoped that they would do their first drilling before the end of 2012). So when they were told that they could suggest where the rover should go in order to do all these first-time activities, they faced a choice. Start the trip toward the southwest, and Gale crater's central mountain, where there are rocks that orbiting missions indicate are super cool? Or drive a few hundred meters northeast, to a rock that looks interesting from space but we don't know what it is that gives it its unusual properties?

It was a tough choice. Driving southwest would get them to the mountain faster, but at a scientific cost: these first five or six months of initial work would be performed on rocks that don't look particularly notable from orbit. Driving northeast would delay their arrival at the mountain, but there was a chance that this rock that looked interesting from space would turn out actually to be interesting when seen on the ground, so they might get some good science done during the testing period.

The Curiosity science team gambled on the closer target. And they won. The stuff at Glenelg turns out to be a sequence of diverse sedimentary rocks that seem to have been deposited by liquid water, then turned into rock, which was, some time later, saturated again with liquid water, leaving concretions and gypsum veins in their wake. Water, water, everywhere, and at multiple times in history, in multiple depositional environments! It's exactly the kind of stuff Curiosity was sent to Mars to study. Project scientist John Grotzinger said today that if they had driven all the way to the mountain and found the kinds of rocks they found at Glenelg, they would have been very happy. In fact, the reason that the drilling was delayed from before until after Christmas is because the scientists wanted to spend more time figuring out the geologic context for these fascinating rocks.

So, what have they found? First, here's a look at where Curiosity has driven so far, courtesy of space mapper extraordinaire Phil Stooke: