Mars and Earth: With a radius of 3,390 kilometers, Mars is about half the size of Earth. If Earth were the size of a nickel, Mars would be about as big as a raspberry.

Phobos and Deimos: Mars has two small moons, Phobos and Deimos, which are potato-shaped because they have too little mass for gravity to make them spherical. Mars' moons get their names from the horses that pulled the chariot of Ares, the Greek god of war.

Martian day: As Mars orbits the Sun, it completes one rotation every 24.6 hours, which is quite similar to an Earth day (23.9 hours). Martian days are called sols – short for "solar day." A year on Mars lasts 669.6 sols, which is the same as 687 Earth days.

The 'God of War': Mars was named by the ancient Romans for their god of war because its reddish color was reminiscent of blood. Other civilizations also named the planet for this attribute, the Egyptians calling it "Her Desher," meaning "the red one."

The Red Planet: Mars is actually many colors. At the surface, we see colors such as brown, gold, and tan, however, Mars looks reddish due to oxidization or rusting of iron in the rocks, regolith (Martian “soil”), and dust of the red planet.

Life on Mars: While scientists don't expect to find living things currently thriving on Mars, they're looking for signs of life that existed long ago, when the planet was warmer and covered with water.

How Mars was formed: Our solar system settled into its current layout about 4.5 billion years ago, and Mars formed when gravity pulled swirling gas and dust in to become the fourth planet from the Sun.