astroengine writes "Scientists are beginning to sketch out plans for NASA's new Mars rover Curiosity to climb Mount Sharp, but future robots may have a more direct way to access the planet's history books. Recent discoveries of 'skylights' and lava tubes on the surface of Mars, as well as the moon, are sparking the development of robotic probes that can descend into caves and explore tunnels. 'Geology works in layers, so how many layers can you see? Well, we know there are sinkholes on Mars. Those sinkholes expose potentially hundreds of feet of layers, so if you could lower something down and examine those layers and explore a tunnel underneath, or anything of that sort, the science that can be done with that is just phenomenal,' Jason Derleth, senior technology analyst with NASA's Innovative Advanced Concepts Program, told Discovery News."