Most of the areas in the Northern Hemisphere consist of flat, low-lying plains in its many regions. The lowest northern regions are considered to be among the most flattest, smoothest places in the solar system and they are so smooth because they were built up from deposits of sediment, tiny particles that settle to the bottom of a liquid.
There is some evidence that water once flowed across the Martian surface, and the water would have tended to collect in the lowest spots on the planet resulting in having sediments deposited there.
Balles Marineris is a canyon system that lies on the equator of Mars. In Latin, the name stands for Valleyes of Mariner, a space probe called Mariner 9 discovered the canyons in 1971. The cayons run from east to west for about 2,500 miles, 4,000 kilometers, which is said to be be the width of Australia or the distance from Philadelphia to San Diego.
Mars has the largest volcanoes in the solar system, its tallest one is called Olympus Mons. Olympus Mons is latin for Mount Olympus and it rises 17 miles, 27 kilometers, above its surrounding plains. It is also 370 miles, 600 kilometers, in diameter and has slopes much like Earth's Hawaiian volcanoes. The three other large volcanoes, Arsia Mons, Ascraeus Mons, and Pavonis Mons sit atop an broad, uplifted region called Tharsis.
Craters and Impact Basins
Mars craters have deep, bowl-shaped floors with raised rims, its large craters can have central peaks that form if the floor rebounds upward after an impact. The southern hemisphere is old so it has many craters while parts of mars, like the northern hemisphere, are younger and have fewer craters than the south.
Volcanoes have few craters thus, meaning they have erupted recently. The lava from the volcanoes could have covered any other craters that were there during and before the eruption, and not enough time has passed for new craters to form.
"Some of the impact craters have unusual-looking deposits of ejecta, material thrown out of the craters at impact. These deposits resemble mudflows that have solidified. This appearance suggests that the impacting bodies may have encountered water or ice beneath the ground."(Nasa)
The polar regions of mars are deposits of thick stacks of finely layered material. Scientists believe that this material is a mixture of ice and dust in layers, and that these deposits extend from the poles to latitudes of 80 degrees in both hemispheres.
Scientists think that the layers may provide the evidence for seasonal weather and long-term change in the Martian climate. Because of the planet's obliquity, the variation alters the amount of sunlight reaches the different parts of Mars. The variation in sunlight may be the cause why Mars has a change in climate there of and past climate changes could have affected the rate in how the atmosphere deposited dust and ice into its current layers.
The additional ice caps come from the layers of frost during the winter that never melt but freeze to make a new cap above the rest of the layers. The frost is made of solid carbon dioxide, CO2/
dry ice, that was condensed from the CO2 gas in the atmosphere. The frost goes from the poles to as low 45 degrees in latitude, which is about halfway to the equator.