Viewpoint: Yes, evidence from various Mars missions indicates that water once flowed on Mars and helped shape the current landscape.

Viewpoint: No, the topographical features suggesting that water once flowed on Mars lack crucial elements necessary to support the theory that water flowed on Mars.

People have wondered about the planet Mars for hundreds of years. Mars is Earth's closest neighbor in the solar system, and it is close to Earth in size and appearance as well. While Mars presents no obvious bodies of water, polar ice caps on the planet grow and shrink with the seasons. Yet more intriguing to observers are the mysterious channels visible on the Martian surface. The appearance of these channels have led to speculations about the presence of water on Mars. While modern telescopes and exploratory...