Where’s the first place you’d look for maps of Mars?If you didn’t say Google Earth, why not? After all, a 3D mapping tool of Mars was added to Google Earth for the 5.0 release. But Google today announced an update to the program that includes historical maps and images, a stream of the latest images from the Red Planet and not one, but TWO guided tours of the fourth rock from the Sun.In the Google Earth toolbar, you can select “Mars,” and you then swoop in on the planet, with a 3-D view that includes layers