If you asked a planetary scientist in 1960 to describe Mars, the description would have been something like this: Mars is pretty flat, with a few rolling hills. Its atmosphere is made mostly of nitrogen. It has an atmospheric pressure similar to Earth's. The polar caps are nothing more than a wafer-thin hoarfrost. The dark areas on the planet's surface are old sea beds probably filled with primitive organic material or vegetation of some kind, and the planet has naturally formed channels of water.
Every one of these beliefs, it turns out, was wrong. Observations made standing on Earth 35 million miles away simply couldn't provide an accurate picture or understanding of Mars.
