Mars

Mars is the fourth planet from the Sun. Mars has been known and observed since ancient times, and is known as "The Red Planet", due to of its iron rust that causes its reddish hue. Mars has two known moons, named Phobos and Deimos.

Atmosphere
Mars' atmosphere mostly consists of carbon dioxide. In fact, it makes up 95% of the. The rest is made up of 3% nitrogren, about two percent argon, and the rest are trace gases such as water and oxygen. The atmosphere of Mars is much less dense than that of Earth's. The atmospheric pressure of Earth's atmosphere at about fourty kilometers in altitude would equal that of the atmospheric pressure of Mars at surface level.

Geographical Features
Mars is home to the highest mountain the Solar System named, which means "Mount Olympus". It is more than three times the height of Mount Everest, reaching 27 km in height. Olympus Mons is actually an extinct volcano called a dormant volcano. It does not erupt anymore because the vent of the volcano is shut, as seen in the picture.

Another geographical feature is the Valles Marineris, which means "Mariner Valleys". It is 700 km in width, leaving the Grand Canyon in the dust only reaching 20 km in width. It is believed this valley was flooded with water in the past.

Orbit/Rotation
Mars makes one orbit around the Sun in approximately two Earthen years. Mars' aphelion is around one hundred forty one million, five hundred thousand miles, or 1.2 AU from the Sun. The perihelion is around one hundred forty five million miles, or about 1.5 AU. Although, this orbit period can be perturbed by neighboring objects in the nearby Asteroid belt, and even the Earth.

Volcanism
The volcanic activity, more referred to as volcanism, has caused lava flows over the few millions of years, leaving behind trenches on the surface that can be viewed through even amateur telescopes on Earth. Examples of volcanism can be traced by to Olympus Mons, which is a possibly dormant shield volcano on the surface of Mars. It has not erupted in thousands of years, yet its last eruption shot a replete of debris into the atmosphere, causing a blackout for weeks. The lava is actually black.

Moons
Mars harbors two moons in its gravitational pull, named Phobos and Deimos. Phobos, the larger and denser of the two, is home to the Stickney crater, a crater that is easily spotted to the right of the moon. Phobos was discovered by Asaph Hall in 1877. The next moon, Deimos, is the smaller and more irregular-shaped moon, which stands to reason that it was an inhabitant of the Asteroid belt. It was too discovered by Asaph Hall in the same year.