How do you know so much about the surface of Mars when no man has ever set foot on the planet?

Answer 1

We know the specific answers to specific questions that the probes were designed to find out. There have been several Mars landers, starting with two Viking probes that landed on July 20, 1976. (The first one was supposed to land on July 4, 1976 on the Bicentennial day - but there were Martian duststorms that lasted for weeks. So it landed on the anniversary of the Apollo 11 landing on the Moon.)

Then the Mars Rover landed in the 1990's, and then two more - Spirit and Opportunity - five years ago. Between the satellite Photography and the landers, we learned a LOT about Mars from our robot probes.

Answer 2

Scientists have studied Mars using various instruments, such as satellites and rovers, that have provided data and images of the planet's surface. By analyzing these observations, scientists have been able to learn a lot about Mars' geology, climate, and atmosphere without physically sending humans to the planet.