Then Mariner 9 arrived during a planet-wide dust storm. Mars looked even more boring. But then the dust began to settle, and out of the clouds emerged the distinctive shape of what looked like the tops of volcanoes. And if Mars was once volcanically active, then it might have had an atmosphere... water... possibly even life.

The Mariners also showed us a giant canyon system, "Valles Marineris", the "Valleys of the Mariner," a huge canyon named for the spacecraft. On your computer or TV it may look small, but this canyon would stretch from New York to Los Angeles!

The first American missions were called "Mariner" and there were 9 of them. Mariner 4 flew by and showed a world that looked as dead as Earth’s moon. It looked as if Lowell and Schiaparelli were completely mistaken.

Then in 1976, two "Viking" spacecraft arrived at Mars. Each included a lander and an orbiter.

The Vikings showed us a dead surface and lots of craters, but also what certainly looked like signs of flowing water in the past, like these tear drop-shaped islands, and what seemed to be river channels carved by streams.

So where did all the water that might have made those channels go?

That’s one of the mysteries of Mars being studied by more recent missions.