answer: #Person2# saw a science program about Mars last night. #Person1# heard on the TV that the US successfully sent explorers to Mars.
documents: #Person1#: Did you watch TV last night, Rose?
  #Person2#: Yeah. I saw a science program. It was quite interesting.
  #Person1#: What was it about?
  #Person2#: Mars. Scientists say there might be water on it.
  #Person1#: If so, we may live there someday.
  #Person2#: I hope so. Did you know the US successfully sent two robotic explorers to Mars last month?
  #Person1#: 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.
  #Person2#: Yes. Both have sent back pictures of the planet. And the latter did a better job.