Mars: Facts & Overview

Instructor: Katie Chamberlain

Katie has a PhD in Microbiology and has experience preparing online education content in Biology and Earth Science.

The best way to befriend a Martian is probably to understand where it is coming from. Luckily, you can quickly prepare with this crash course covering all the particulars about the planet Mars.


Mars is one of the eight planets that are currently orbiting around our Sun. It is the fourth planet from the Sun, the next furthest after Earth. There are records of Mars dating back thousands of years. Its dark red appearance likely stirred images of a bloody battle, because both the Greeks and the Romans named it after their gods of war: Ares and Mars.



The diameter of Mars is 6,795 km. It is only 15% of the size of the Earth by volume and 10% by mass. The smaller size causes the gravity on Mars to be roughly one-third of the gravity on Earth. Its core is likely composed of metals like iron, sulfur, and nickel. Since Mars does not have a global magnetic field, it is believed that its core is solid.

The orbit of Mars ranges from 206 million to 249 million km from the Sun. It takes 687 Earth days for Mars to complete its orbit, which is nearly twice as long as Earth's solar year. However, its day is nearly identical to Earth's at 24.6 hours.


On the surface, Mars is covered in a loose rocky material called regolith. The regolith has a high iron content that leads to its rusty red color. The atmosphere is much thinner than the Earth's and contains mostly carbon dioxide.

The surface of Mars is very dry because there is no liquid water present. While water ice has been observed below the surface, liquid water is not likely permitted because of the thin atmosphere. Water ice and frozen carbon dioxide are plentiful at Mars's polar ice caps, which grow and shrink according to the seasons.

Surface of Mars
Surface of Mars

The temperature on Mars ranges from -125 to 20 degrees Celsius. Despite occasional balmy temperatures, it would not be a nice vacation destination because of the large dust storms. They often last for months at a time and can cover the entire planet.

Big features

Mars has quite a few huge geological features. Perhaps the most famous is the Olympus Mons volcano, the highest known mountain in the solar system. It measures 25 km high (three times higher than Mt. Everest) and covers a space as large as the state of Arizona.

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