Did you watch TV last night , Rose ?   Yeah . I saw a science program . It was quite interesting .   What was it about ?   Mars . Scientists say there might be water on it .   If so , we may live there someday .   I hope so . Did you know the US successfully sent two robotic explorers to Mars last month ?   Sure . I heard about this on the TV . On January 3rd , 2004 , Explorer Spirit landed near the so-called Guser Crater . And three weeks later , Spirit's twin explorer , Opportunity , landed on Meridian Planum named by scientists . 