Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury.

Mars is a terrestrial planet with a thin atmosphere, with surface features reminiscent of the impact craters of the Moon and the valleys, deserts and polar ice caps of Earth.

Discovered: Known to Ancients

Planet Type: Terrestrial Planet

Average Distance from Sun: 142 million miles

Equatorial Diameter: 4220 miles

Axil Tilt (to orbit): 25 °

Inclination to Ecliptic: 1.85 °

Length of Day (rotation period): 24 hours, 37 minutes

Length of Year (orbital period): 687 days

Orbital Eccentricity: ~0.093

Surface Gravity (amount times Earth gravity): .375

Surface Temperature: -81 ° F.

Moons: 2.

Rings: None

Mars is approximately half the diameter of Earth, with a surface area only slightly less than the total area of Earth's dry land.

Mars is often referred to as the Red Planet which refers to the effect of the iron oxide prevalent on the surface of Mars, giving it a reddish appearance distinctive among the astronomical bodies visible to the naked eye.

The red-orange appearance of the Martian surface, caused by iron oxide or rust can have different colors, which entirely depends on the minerals present. In fact, the surface can look like butterscotch, golden, brown, tan, and greenish.

The two moons of Mars are Phobos and Deimos, both are irregular in shape, and both were discovered by American astronomer Asaph Hall in August 1877.

There are no total solar eclipses on Mars, as the moons are far too small to completely cover the Sun. On the other hand, total lunar eclipses of Phobos happen almost every night. Both moons are tidally locked, always presenting the same face towards Mars.

As with most of the celestial objects in our solar system, these two moon are named after the Greek mythological twin characters. These two are, Phobos (fear and panic) and Deimos (terror and dread) who accompanied their father Ares into battle. Ares, is the god of war and was known to the Romans as Mars.

Equatorial Diameter: 16.8 miles.

Rotation Period: 7.3 hours

Orbital Period: 7.3 hours

Orbital Distance: 5,832 miles

Surface Temperature: -40°F

Phobos is so close to Mars that it orbits Mars faster than Mars rotates and appears to rise and set twice each Martian day.

Speedy Phobos rises in the west, sets in the east, and rises again in just eleven hours.

Since Phobos orbits Mars faster than the planet itself rotates, tidal forces are slowly but steadily decreasing its orbital radius. At some point in the future, when it approaches Mars closely enough, Phobos will be broken up by these tidal forces and form a ring around Mars or will crash into Mars.

Several strings of craters on the Martian surface, inclined further from the equator the older they are, suggest that there may have been other small moons that suffered the fate expected of Phobos, and that the Martian crust as a whole shifted between these events.

Equatorial Diameter: 9.31 miles.

Rotation Period: 30.3 hours

Orbital Period: 30.3 hours

Orbital Distance: 14,580 miles

Surface Temperature: -40°F

Deimos is slowly moving farther away from Mars and it is believed that it will eventually leave orbit from Mars.

Deimos, being only just outside synchronous orbit, rises as expected in the east but very slowly. Despite its 30-hour orbit, it takes 2.7 days to set in the west as it slowly falls behind the rotation of Mars.

Deimos is far enough away that its orbit is being slowly boosted instead, as in the case of Earth's Moon.