Martian Soil

What is Mars Made Of? Composition of Planet Mars

Mars is the "Red Planet" for a very good reason: its surface is made of a thick layer of oxidized iron dust and rocks of the same color. Maybe another name for Mars could be "Rusty." But the ruddy surface does not tell the whole story of the composition of this world.Martian soil does not have all of the same components of Earth’s soil. In fact, the soil on Mars is almost entirely made up of mineral matter, with small amounts of water (See Figure 1). Since living things do not exist on Mars, its soil does not have organic matter. There is no air in Martian soil, since air is specific to Earth’s atmosphere. Mars’ atmosphere is 96% carbon dioxide, with other gases in very small amounts, but it is 100 times less dense than Earth’s atmosphere (see Earth vs. Mars). Because Mars’ atmosphere is so thin, there is very little atmospheric gas in the Martian soil. The mineral matter in Martian soil comes from weathered volcanic rock. It has clay and silt-sized particles, but it is overall a sandy soil. There is also a thin surface layer of very small dust particles. The soil has a reddish color because it contains a lot of iron oxides (rust). It is similar to iron-rich volcanic soils on Earth. In fact, NASA has made a Mars soil simulant that comes from volcanic soil in Hawaii. In contrast to Earth, the soil on Mars is relatively homogenous (the same everywhere), because global dust storms move the soil around the planet. Earth has a lot of water in oceans, lakes and rivers, and precipitation is common. In contrast, Mars is extremely dry. It has solid water ice, but very little liquid water. No water-based precipitation reaches the planet’s surface. This means that the soil on Mars is also extremely dry, containing just 2% water. Scientists think that the water in Martian soil is absorbed from vapor in the planet’s atmosphere. NASA’s Curiosity rover is studying samples of Martian soil and rock to learn more about its composition and properties

Dusty crust

The dust that covers the surface of Mars is fine like talcum powder. Beneath the layer of dust, the Martian crust consists mostly of volcanic basalt rock. The soil of Mars also holds nutrients such as sodium, potassium, chloride and magnesium. The crust is between 6 and 30 miles (10 and 50 kilometers) thick, according to NASA.

Mars' crust is thought to be one piece. Unlike Earth, the red planet has no tectonic plates that ride on the mantle to reshape the terrain. Since there is little to no movement in the crust, molten rock flowed to the surface at the same point for successive eruptions, building up into the huge volcanoes that dot the Martian surface.

Dusty, glass-rich sand dunes like these found just south of the north polar ice cap could cover much of Mars. (False color image) (Image credit: NASA/JPL/University of Arizona)

That doesn't mean the crust sits quietly. New research has found that powerful landslides may speed down Martian slopes at up to 450 mph (725 km/h).

"The calculated velocity of landslides (often well in excess of 100 m/s and up to 200 m/s at peak) compares well with velocity estimates based on the run-up of the landslides on mounds," researchers wrote in a study published in The European Physical Journal Plus.

"We conclude that ice may have been an important medium of lubrication of landslides on Mars, even in equatorial areas like Valles Marineris" (the Grand Canyon of Mars).

Any life that ever existed on Mars would have had to cope with the radiation, perhaps by thriving underground. While astronomers continue to search for past or present signs of biology on Mars, no convincing evidence has yet been found.

Mantle and core

Evidence suggests there have been no volcanic eruptions for millions of years, however. The mantle that lies beneath the crust is largely dormant. It is made up primarily of silicon, oxygen, iron, and magnesium and probably has the consistency of soft rocky paste. It is probably about 770 to 1,170 miles (1,240 to 1,880 km) thick, according to NASA.

The center of Mars likely has a solid core composed of iron, nickel and sulfur. It is estimated to be between 930 and 1,300 miles (1,500 and 2,100 km) in diameter. The core does not move, and therefore Mars lacks a planet-wide magnetic field. Instead, it has sporadic field lines that scientists have nicknamed "Christmas Lights." Without a global magnetic field, radiation bombards the planet making it relatively inhospitable compared to Earth.

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