Ever wondered how you might navigate your way across the surface of Mars, if you ever find yourself there? Well, perhaps you could use this: the most detailed map of the Red Planet's geology ever made. The map compiles 16 years' worth of observations from four orbiting spacecraft (Mars Global Surveyor, Mars Odyssey, Mars Express and Mars Reconnaissance Orbiter) into a single, super-detailed chart. In fact, it's the first of its kind made since 1987. You can download a huge poster-sized version of it from the US Geological Survey website. [US Geological Survey via New Scientist]