1.   If a place like Antarctica was discovered on another planet, scientists from Earth undoubtedly would send hardy robot spacecraft to explore such an intriguing but desolate frozen world.

2.   Indirect evidence comes in the form of spectacular close-up photos of Mars, snapped by a robot spacecraft.

3.   So the American robot spacecraft Mars Pathfinder is headed there for a landing Friday, the Fourth of July.

4.   Water is crucial to plans for exploring Mars with robot spacecraft to find evidence of life, and for possible visits by humans in the future.

5.   Water is crucial to plans for exploring Mars with robot spacecraft to find evidence of life, and for possible visits by humans.