1. Exploring Mars: The Inside Story
Walter S. Kiefer
Lunar and Planetary Institute

2. The Interior of Mars
A schematic view of the interior structure of Mars: an iron-rich core and a rocky mantle and crust. Studies of the abundances of certain radioactive elements in martian meteorites show that the iron and rock differentiated (or separated) into distinct layers within about 30 million years of the planet’s formation.

3. Olympus Mons
This is a three-dimensional perspective view of Olympus Mons. The volcano is nearly 14 miles (22 kilometers) high, which is twice as high as passenger airplanes usually fly. The depression in the center is known as a caldera. It is 50 miles (80 kilometers) across and 2 miles (3 kilometers) deep. When eruption of magma on the sides of the volcano left portions of the summit rock unsupported, a series of giant collapse events produced the caldera. Similar calderas are found at volcanos on Earth such as in Hawaii.

4. Big Volcanos
Volcanos on Mars can be very large. This image shows the 4 largest volcanos to the same scale as the United States. The largest volcano on Mars (and in the entire Solar System) is Olympus Mons at the upper left of the image. It is about 400 miles (650 kilometers across), large enough to cover Washington state and half of Oregon. The circle in Texas is the same size as Olympus Mons.

5. Telling Time: Superposition
Superposition means that the youngest things are usually at the top of the stack. It is true for your desk and your laundry pile, and it is true for rocks too! The images here are of the sequence of sedimentary rocks in the Grand Canyon. The rocks at the bottom of the Grand Canyon are more than 1 billion years old. Those at the top are about 250 million years old.

6. Ulysses Patera
Ulysses Patera is 100 km (60 miles) across and 1.5 km (1 mile) high, similar in size to some Hawaiian volcanos. Its base is probably buried by 2-3 km of lava flows. Like Olympus Mons and the Hawaiian volcanos on Earth, Ulysses Patera is made of basalt, which is the most common type of volcanic rock on Earth.

7. Mantle Plumes Temperature
Volcanos such as Olympus Mons on Mars and Hawaii on Earth are formed in places where the interior of Mars (or Earth) is hotter than normal. The colors in this computer model represent temperature, with red being hot and blue being cold. The hot material, known as a mantle plume, is solid but can move very slowly as a viscous fluid at a rate of a few inches per year. Just as hot air rises in our atmosphere, hot rock is more buoyant than cold rock and tends to rise toward the surface of the planet. When the hot material approaches the surface of the planet, the reduction in pressure allows it to melt (white zone) and the resulting magma can erupt at the surface to form a volcano.
Temperature

8. Plate Tectonics
The Earth’s surface is divided into about 12 geologic plates of varying size, which move across the interior of the Earth. Most volcanos and earthquakes are concentrated at the boundaries between the plates.

9. Hawaii-Emperor Volcanic Chain
On Earth, the various geologic plates move across the Earth’s surface at a speed of a few inches per year. As a result, magma coming up from a mantle plume (previous slide) can only reach a given location for a short period of time, so that most volcanos are relatively small. This map shows the topography of the sea floor in the Pacific Ocean. Most of the ocean is 2.5 to 5 kilometers deep (1.5 to 3 miles, purple and blue colors). The red spots in the lower right of the image to the upper left are volcanos formed as part of the Hawaiian Island chain. The dashed black line highlights the full length of the volcano chain. Some are completeley buried under water, but are still much higher than the surrounding plains (the underwater structures are known as the Emperor seamounts). Each of these islands and seamounts is a separate volcano (or small group of volcanos) formed as the Pacific plate moved over the Hawaiian mantle plume. On Mars, the surface does not move; as a result, it stays over a mantle plume for a long period of time and results in a small number of very large volcanos, such as Olymups Mons, rather than many small volcanos.

10. Global Topography
Colors in this image represent elevation. Dark blue is lowest, green and yellow are intermediate in height, red and brown are high, and the highest regions are white. All of the highest regions are volcanos, including Olympus Mons in the upper left. The long linear low zone in the left center of the image is Valles Marineris. The circular low spot (dark blue) in the lower right is Hellas, a 2300 km (1400 mile) diameter impact basin. Hellas formed when Mars was struck by an asteroid or comet that was probably miles across. Many other circular structures are visible in this image – these are all impact craters, formed in a similar way to Hellas.

11. Valles Marineris
Valles Marineris is a giant trough on Mars, more than 4000 kilometers (2500 miles) long and up to 10 km (6 miles) deep. It is long enough that it would reach from California to Washington D.C. on Earth! Valles Marineris formed in the middle part of martian history, roughly 2.5 to 3.5 billion years ago, when forces in the crust of Mars stretched the surface and created massive faults, resulting in the deep valley that crosses the center of this image.

12. Valles Marineris vs. Grand Canyon
The Grand Canyon in Arizona (seen here in a picture taken on the Space Shuttle) formed when the Colorado River eroded down through the various rock layers, producing a canyon that is about 1 mile deep. The river can be seen at the bottom of the canyon, and the natural meandering of the river results in the canyon’s curved shape. The various branches of the canyon formed where different river systems flowed into the main river. In contrast, the Valles Marineris on Mars (top left image) has no river at the bottom of it. The view shown here is about 300 miles across and is very straight – any such long, straight feature is likely to have formed by the motion of faults.
Grand Canyon

13. Planetary Faulting
This cartoon shows two different ways faults can produce surface features on Mars or Earth. If a region is extended or stretched apart (top), the fault motions can produce a deep valley such as the Valles Marineris. Alternately, if the region is compressed or pushed together (bottom), a ridge or mountain can be formed.

14. Martian Meteorites Shergottite RBT04262
Meteorites from Mars provide important constraints on the chemical composition and structure of Mars. About 60 such meteorites are currently known, and are distinguished from other types of meteorites by differences in their composition. Many of these meteorites have been collected in Antarctica, as shown in this figure.
Shergottite RBT04262