Mars
Olympus Mons
http://en.wikipedia.org/wiki/Mars
Mars is the fourth planet located 1.5 AU away from the Sun. It is often called the red planet for that is how it looks from Earth. The red color comes from the iron rich soil on Mars. When the iron rusts the reddish color appears. Mars has 2 ice caps at the north and south poles. It also has 2 moons orbiting it. Phobos and Deimos, most likely asteroids captured from the asteroid belt. Mars is smaller than Earth and Venus. It's mass is 0.107 of Earths. There are currently 3 satellites orbiting Mars. The Mars Odyssey, Mars Express, and the Mars Reconnaissance Orbiter. There are also the two twin rovers, Spirit and Opportunity, and the Phoenix Mars Lander. The Phoenix Mars Lander Has directly sampled water in shallow Martian soil. There is a possibility that there is or was life on Mars. The tallest mountain and volcano in the solar system, Olympus Mons, is located on Mars.
http://cseligman.com/text/planets/marsstructure.htm
Structure:
Mars's core contains more sulfur and less iron than its neighbors. It is mainly iron with15-17% sulfur. The radius is between 1,500-2,000 km. The large sulfur composition gives it a low viscosity. We are now concluding that Mars has a liquid core. Some believe that this core is slowly solidifying.
Mars has a molten silicate mantle surrounding the core. It is between 1,300-1,800 km in thickness. It formed many of the volcanic and tectonic features of this planet.
Mars has a thin surface that is covered with volcanoes, rift valleys, and plains. Plate tectonics have not been discovered yet. The ice caps are mainly frozen carbon dioxide. there are signs of riverbeds, shorelines, and canyons that are believed to be carved out by giant rivers. The crust is 25-70 km thick.
Mars's atmosphere contains 95.32% carbon dioxide, 2.7% nitrogen, 1.6% argon, 0.13% oxygen, 0.07% carbon monoxide, 0.03% water vapor, and 0.013% nitric oxide . There have also been small readings of methane in the atmosphere which could mean there is life. It could also be because of a geochemical process. It also contains a large amount of dust. Dust Devils (tornadoes) are frequently spotted on Mars.