Earth's Neighbor Mars is about half the size of Earth. In some ways, Mars is similar to our planet. However, there are also many differences. the planet Mars A As on Earth, there are mountains on Mar However, they are much larger than Earth's mountains. One of them is the largest volcano in the Solar System. It is three times as high as Mount Everest. Unlike Mount Everest, its sides aren't steep. It's also flat on the top. Mars also has roc ky canyons, just like Earth. They are much larger than Earth's. One of the 10 canyons is 4,000 km long and 200 km wide. It is amazing to see! Sometimes asteroids' hit planets. When this happens, they create craters. This happens to Earth, too. But asteroids hit Mars much more often than they hit Earth. Scientists think that an asteroid larger than Pluto hit Mars. When this happened, it threw dirt into the air. 15 That dirt covered an area as big as the United States!