Compelling arguments can be made for the interpretation of at least the vast majority of Martian volcanism as being basaltic in nature.
|Olympus Mons - a Martian shield volcano. Click image for closer view.|
The absence of plate tectonics on Mars results in the absence of the belts of silicic composite stratovolcanoes found here on Earth. Instead, Mars exhibits hot-spot volcanism resulting in the development of shield volcanoes similar to the basaltic landforms found on Earth (Hodges and Moore, 1994).
|Lava flows in the Elysium region. Click image for closer view.|
Studies of Mars' moment of inertia can provide estimates of the distribution of iron between the core and mantle of Mars. Preliminary studies indicate a 16 to 27 percent FeO composition of the Martian mantle, as opposed to the 8 to 11 percent for the Earth. Higher iron content in the mantle should lead to lower viscosity lavas (McGetchin and Smyth, 1978).
Analysis of the soil samples collected by the Viking landers in 1976 indicate iron-rich clays consistent with weathering of basaltic rocks (Francis, 1993).
The discovery of meteorites (the SNC's) on Earth that apparently have a Martian origin provides first-hand evidence of the nature of Martian volcanism. These include actual basaltic samples. Analysis of the FeO content of the Shergotty meteorite shows a concentration of 18 percent, in agreement with the predictions mentioned above (Dodd, 1986; Francis, 1993).
Martian meteorite. Johnson Space Center Image. Click image for closer view.
Content assembled by Brian H. Day, Margaret McCrary, and Bill Frye.
Curator: Brian H. Day.
Responsible NASA Official: Donald James