Dean: Did you watch TV last night, Rose?

Rose: Yeah. I saw a science programmer. It was quite interesting.

Dean: What was it about?

Rose: Mars. Scientists（研究火星的科学家） say there might be water on it.

Dean: If so, we may live there someday.

Rose: I hope so. Did you know the U.S. successfully sent two robotic explorers to Mars last month?

Dean: Sure. I heard about this on the radio. On January 3rd, 2004, Explorer Spirit landed near the so-called Gusev Crater. And three weeks later, Spirit’s twin explorer, Opportunity, landed on Meridiani Planum named by scientists.

Rose: Yes. Both have sent back pictures of the planet. And the latter did a better job.