Surface composition

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A predominant feature of the Martian surface is the iron oxide-rich dust known as regolith, giving the planet its characteristic red color. This dust is very fine and the result of years of meteorite impacts pulverizing the Martian surface spreading dust around the planet. This dust is blown globally by storms, creating massive seasonal dust storms that can last for months.

Rock formations on the surface are primarily composed of basalt - a consequence of the extensive lava flows that once existed as a result of ancient geological activity. Analysis of soil samples collected by the Viking landers in 1976 indicate iron-rich clays consistent with weathering of basaltic rocks.

Panorama taken on the rim of Erebus crater

There is also evidence the Martian surface may be more silica-rich than the basalt created by lava flows, similar to andesitic rocks found on Earth (rock which crystallizes from silicate minerals at intermediate temperatures).

Mars has twice as much iron oxide in its outer layers as Earth does, despite their similar origin (meteorite impacts). This is due to the geologically active (and hotter) Earth transporting much of the surface iron deep below the terrestrial surface. Mars does not have this geological advantage to produce heat, so the iron remains in the Martian regolith, giving Mars its red glow.


Chemical composition of the soils on Mars is based upon the various data we have to date from Mars landers as well as SNC-meteorites believed to be from Mars. Different sites and sources contain different concentrations.

Spirit, Opportunity, Curiosity Rovers[1]

Values estimated from a graph. Measurements provided by their Alpha Particle X-ray Spectrometer (APXS). Spirit data taken from 59 samples at Gusev Crater, Opportunity data taken from 23 samples at Meridiani Planum, Curiosity data taken from a sample inside a rover wheel scuff at Gale Crater.

Spirit     Opportunity   Curiosity
(Wt%) (Wt%) (Wt%)
SiO2 Silicon Dioxide 46.0 45.3 43.6
FeO Iron(II) Oxide 16.0 18.8 21.3
Al2O3 Aluminum Oxide 10.2 9.16 9.58
MgO Magnesium Oxide 8.61 7.39 6.55
CaO Calcium Oxide 6.27 6.93 7.39
SO3 Sulfur Trioxide 6.13 5.92 5.16
Na2O Sodium Oxide 3.00 2.20 2.20
P2O5 Phosphorus Pentoxide   0.91 0.84 0.56
TiO2 Titanium Dioxide 0.91 1.05 1.53
Cl Chlorine 0.70 0.64 0.63
K2O Potassium Oxide 0.42 0.49 0.63
Cr2O3   Chromium(III) Oxide 0.35 0.42 0.42
MnO Manganese(II) Oxide 0.28 0.35 0.42
Ni Nickel 0.047 0.045 0.035
Zn Zinc 0.027 0.033 0.027
Br Bromine 0.005 0.008 0.003
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Note: In the image SiO2 and FeO values were divided by 10 to not overrun the boundaries of the image, and Ni, Zn, and Br were multiplied by 100 to be visible.

Viking Lander 1 & 2, Pathfinder, JSC Martian Soil Simulant[2]

JSC Mars-1 is a simulated Martian soil devel­oped for use in: scientific research, engineer­ing studies, and education.

Viking 1   Viking 2   Pathfinder   JSC Mars-1 volatiles   JSC Mars-1 dry
Oxide (Wt%) (Wt%) (Wt%) (Wt%) (Wt%)
SiO2 43 43 44.0 34.5 43.5
Fe2O3 18.5 17.8 16.5 12.4 15.6
Al2O3 7.3 7 7.5 18.5 23.3
SO3 6.6 8.1 4.9 n.a. n.a.
MgO 6 6 7.0 2.7 3.4
CaO 5.9 5.7 5.6 4.9 6.2
Cl 0.7 0.5 0.5 n.a. n.a.
TiO2 0.66 0.56 1.1 3.0 3.8
MnO n.a. n.a. n.a. 0.2 0.3
K2O <0.15 <0.15 0.3 0.5 0.6
Na2O n.a. n.a. 2.1 1.9 2.4
P2O5 n.a. n.a. n.a. 0.7 0.9
Volatiles   n.a. n.a. n.a. 21.8 n.a.
Total 89 89 89.5 101.1 100.0

n.a. = Not Analyzed: all iron calculated as Fe2O3


SNC Meteorites are meteorites ejected from Mars and named SNC after the locations where they were first discovered.

Mantle Crust Name (%)
SiO2 Silicon Dioxide 44.4
Al2O3 Aluminum Oxide 3.02
FeO Iron(II) Oxide 17.9
MgO Magnesium Oxide 30.2
CaO Calcium Oxide 2.45
TiO2 Titanium Dioxide 0.14
Na2O Sodium Oxide 0.50
P2O5 Phosphorus Pentoxide 0.16
Cr2O3 Chromium(III) Oxide 0.76
K Potassium 305ppm
Ni Nickel 400ppm


  1. 2012. Inspecting Soils Across Mars. [online] Available at: <> [Accessed 18 October 2021].
  2. Allen, C., Jager, K., Morris, R., Lindstrom, D., Lindstrom, M., & Lockwood, J. (1998). Martian soil stimulant available for scientific, educational study. Eos, Transactions American Geophysical Union, 79(34), 405-405.
  3. P. Cattermole, Mars: The story of the Red Planet, (Springer Science & Business Media, Dec 6, 2012 - Science), page 51, Table 5.1.