Surface composition

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Overview

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 is 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.

Materials

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

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

		Spirit	Opportunity	Curiosity
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

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

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
Al2O3	7.3	7	7.5	18.5	23.3
TiO2	0.66	0.56	1.1	3.0	3.8
Fe2O3	18.5	17.8	16.5	12.4	15.6
MnO	n.a.	n.a.	n.a.	0.2	0.3
CaO	5.9	5.7	5.6	4.9	6.2
MgO	6	6	7.0	2.7	3.4
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
SO3	6.6	8.1	4.9	n.a.	n.a.
Cl	0.7	0.5	0.5	n.a.	n.a.
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

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