So let me tell you about the ______ adventure we're about to ______. But first, a few ______facts about where we're going. This picture actually ______the true size of Mars compared to Earth. Mars is not our sister planet. It's far less than half the size of the Earth, and yet despite the fact that it's smaller, the surface area of Mars that you can stand on ______ the surface area of the Earth that you can stand on, because the Earth is mostly covered by water.