Mars

Mars
Description
Adjectives:	Martian
Distance from Sun:	227.9 million km
Diameter:	6,779 km
Radius:	3,390 km
Temperature:	438 K
Known Moons	2

Mars is the second smallest planet in our Solar System and the fourth planet from the Sun. Mars has two moons, Phobos and Deimos. It was said that billions of years ago, Mars was filled with oceans and maybe even life.

Atmosphere

The atmosphere of Mars is the layer of gas surrounding Mars. It is primarily composed of carbon dioxide, molecular nitrogen and argon. It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen and other noble gases. The atmosphere of Mars is much thinner than Earth's.

Surface

Mars' surface is a dry, barren wasteland marked by old volcanoes and impact craters. The entire surface can be scoured by a single sand storm that hides it from observation for days at a time. Despite the formidable conditions, Mars' surface is better understood by scientists than any other part of the Solar System, except our own planet, of course.

Mars is a small world. Its radius is half of the Earth's and it has a mass that is less than one tenth. The Red Planet's total surface area is about 28% of Earth. While that does not sound like a large world at all, it is nearly equivalent to all of the dry land on Earth. The surface is thought to be mostly basalt, covered by a fine layer of iron oxide dust that has the consistency of talcum powder. Iron oxide (rust as it is commonly called) gives the planet its characteristic red hue.

Valles Marineris stretches over 4,000 km (2,500 mi) across Mars, mostly east-west just below the equator, as seen in this Viking 1 orbiter image mosaic.

A composite Viking orbiter image of Olympus Mons on Mars, the tallest known volcano and mountain in the Solar System.

In the ancient past of the planet volcanoes were able to erupt for millions of years unabated. A single hotspot could dump molten rock on the surface for millennia because Mars lacks plate tectonics. The lack of tectonics means that the same rupture in the surface stayed open until there was no more pressure to force magma to the surface. Olympus Mons formed in this manner and is the largest mountain in the Solar System. It is three time taller than Mount Everest. These runaway volcanic actions could also partially explain the deepest valley in the Solar System. Valles Marineris is thought to be the result of a collapse of the material between two hotspots and is also on Mars.

The Martian surface is dotted with impact craters. Most of these craters are still intact because there are no environmental forces to erode them. The planet lacks the wind, rain, and plate tectonics that cause erosion here on Earth. The atmosphere is much thinner than Earth's so smaller meteorites are able to impact the planet.

Mars' surface is believed to be much different than it was billions of years ago. Data returned by rovers and orbiters has shown that there are many minerals and erosion patterns on the planet that indicate liquid water in the past. It is possible that small oceans and long rivers once dominated the landscape. The last vestiges of that water are trapped as water ice below the surface. Scientists hope to analyze some of that ice and discover hidden Martian treasures.