Mars is a desert. There are no seas or bodies of water on its surface, but many valleys and canyons suggest that there may hve been water in liquid form at one time on Mars. Like the deserts on Earth, the Martian desert experiences dramatic changes in temperature from day to night. In the daytime, the soil quickly absorbs the heat of the sun and the temperature can rise up to nearly 70°F. At night, the soil just as quickly gives up the sun's energy and temperatures drop off to below zero again. These effects are due in part to the fact that the thin a atmosphere is unable to hold heat, and is also due to the soil's low thermal inertia , or how quickly it reacts to a change in energy.
Mars shows signs of tectonic activity not entirely unlike the tectonic activity on earth. Mountains, valleys and chasms can be seen all over the planet's surface, and many are believed to have been shaped by faults and crust fractures. Three volcanoes also dot the surface of Mars, each of them over sixteen miles high! It is believed that these Martian volcanoes are currently inactive.
Mars has two polar ice caps, just like we have here on Earth. Unlike Earth's ice caps, however, the Martian caps are made of condensed carbon dioxide, commonly known as dry ice. In the wintertime of each hemisphere, the dry ice caps can expand and extend to almost 45° latitude! In the summer, they sublimate away to just 400 miles in diameter.
