4. MARS This is Mars. It’s cold and lifeless but humans have some robots there driving around and checking it out. It’s the fourth planet from the Sun and we hope to visit it sometime soon. This is one of the first pictures taken by Earthlings using robots on Mars. This is the largest known volcano in the solar system. It’s called Olympus Mons – a Martian shield volcano over twenty kilometers tall. That’s two and a half times the height of Mount Everest. Mars has two moons. This one is called Phobos. It is very small and does not have an atmosphere. It is not big enough to be rounded by its own gravity. These are Curiosity Rover’s tracks. It landed on Mars on August 6th, 2012. Here’s a video of it falling to the Martian surface.