Mars is set to get its latest visitor Sunday night when NASA's new robotic rover, named Curiosity, attempts to land there. Mars has been a prime target for space exploration for decades, in part because its climate 3.5 billion years ago is believed to have been warm and wet, like early Earth.
Here are five other key points:
About the color: It's called the red planet because the landscape is stained rusty-red by the iron-rich dust.
Quick weight loss: Its gravity is only 38 percent that of Earth. So if you weigh 150 pounds (68 kilograms) on Earth, you would weigh 57 pounds (26 kilograms) on Mars.
Hot and cold: Mars' temperatures can range from 80 degrees Fahrenheit (27 Celsius) at its equator to -199 Fahrenheit (-128 Celsius) at its poles.
The air is different: Mars' atmosphere is mostly carbon dioxide with traces of nitrogen and argon. Earth's atmosphere is a mixture of nitrogen, oxygen and other gases.
Longer days: They last 40 minutes longer than a day on Earth.
Explore further: Atmosphere checked, one Mars year before a landing