Mars – The Last of the Inner Planets

Comparison of Mars and Earth in their correct relative sizes. Mars (diameter 6790 kilometers) is only slightly more than half the size of Earth (diameter kilometers).

The mass of Mars is roughly one-tenth the mass of the Earth. Interestingly enough, although Mars is so much smaller than Earth, the lack of water on Mars makes its land surface area roughly equal to the land surface of the Earth.

Mars has the highest mountain in the Solar System. Olympus Mons rises 24 kilometers, or 78,000 feet, from the surface of the planet.

The diameter of of the crater on top of Olympus Mons is more than 600 kilometers (the size of Arizona). The relative ages of the surface in various parts of Mars can be estimated from the number of impact craters present in a given area. Only two craters are visible here, indicating that Olympus Mons is young, probably the youngest volcanic feature on Mars. By some estimates, the most recent large volcanic eruption at Olympus Mons occurred only 25 million years ago. The oldest activity here could be much older than this and would have been buried by younger lava flows.

This image is based on Viking Orbiter images and shows the Tharsis region of Mars with a map of the western United States for scale. The three large, aligned volcanos are Arsia Mons (lower left), Pavonis Mons (center), and Ascraeus Mons (upper right). Olympus Mons is the volcano at upper left, and a portion of Valles Marineris is on the right. Each of the four large volcanos in this figure is at least 400 kilometers across at its base.

This shaded relief painting is based on Viking Orbiter images and shows the Valles Marineris trough system with a map of the United States for scale. Valles Marineris is 4000 kilometers long, nearly enough to stretch from New York to California. Valles Marineris reaches a maximum depth of 10 kilometers. The red box outlines the region shown in the next slide.

The so-called “face” on Mars.

The Face Unmasked This 3D perspective view of the Face using April 8, 2001 laser altimeter data from MOLA was produced by Jim Garvin (NASA) and Jim Frawley (Herring Bay Geophysics). It proves that the “face” is a natural phenomenon, rather than a deliberate creation.

The left image is a portion of Viking Orbiter 1 frame 070A13, the middle image is a portion of Mars Orbiter Camera (MOC) frame shown normally, and the right image is the same MOC frame but with the contrast reversed to simulate the approximate lighting conditions of the Viking image.

In 1877, Giovanni Schiaparelli ( ) announces that he has seen "canali" on Mars. If translated correctly, this announcement would have been interpreted as "channels", but with the excitement building over the Suez Canal, it was translated as "canals", and thus began a detour in the history of Mars exploration.

This image shows data from missions separated by decades that were put together to create the first three- dimensional perspective of the polar regions of Mars

The south polar cap consists mainly of frozen carbon dioxide. This carbon dioxide cap never melts completely. Unlike the south polar cap, the north polar cap probably consists of water-ice.

Just as Earth’s atmosphere can be seen as a blue veil around the planet, Mars’ atmosphere can be seen as a thin, red veil.

The presence of an atmosphere means that weather occurs on Mars. One example of this is the Great Dust Storm of “Perfect Storm” Building on Mars 9/26/01

There is also frost on Mars on occasion, as evidenced by this color enhanced picture of frost at the Viking 2 Lander site

Scientists believe Mar’s interior is like the Earth – with a core, a mantle, and a crust.

While Earth has only one moon, Mars has two - Phobos and Deimos.

The oblong crater to the north of the volcano Ceraunius Tholus is a possible source crater for Martian meteorites. The crater's elongated shape suggests that it formed by a shallow-angle (grazing) impact, which might have helped eject rocks off the Martian surface. These rocks would have orbited the Sun for millions of years before finally landing on Earth.

This painting of a large meteorite impact shows how rocks might be ejected from Mars into space. In a sufficiently energetic impact, rocks from the Martian surface can be ejected with enough velocity to escape the planet's gravity. Painting by Don Davis. Copyright SETI Institute, 1994

A rain of 40 stones fell from the sky in 1911 near Nakhla in Egypt. One meteorite hit and killed a dog. The stones ranged in size from 20g to 1813g, and it is estimated a total weight of 10kg (22 pounds) had fallen. Meteorites from Mars are classed as "SNC meteorites", refering to the places where meteorites of their kind were found (Shergotty-Nakhla-Chassigny).

Researchers have found magnetic material in a 4.5-billion-year-old Martian meteorite that some scientists believe could only have been produced by bacteria.

This meteorite was found on the ice in Antarctica. For scale, the cube at the lower right is 1 centimeter on a side. The meteorite is partly covered by a black glassy layer, the fusion crust. The fusion crust forms when the meteorite enters the Earth's atmosphere at high speed, with friction heating and melting the outer portion of the meteorite. Inside, the meteorite is gray. It formed in a volcanic eruption about 180 million years ago; other Martian meteorites formed in eruptions about 1.3 billion years ago. This meteorite is almost certainly from Mars because it contains a small amount of gas that is chemically identical to the Martian atmosphere. NASA Johnson Space Center S

Rocks are often made of small mineral grains that can't be seen clearly without a microscope. To see these small grains, scientists grind and polish rock samples very thin (0.03 millimeters) so light can pass through them. This picture is a microscopic view, about 2.3 millimeters across, of a martian meteorite. The brown areas are grains of the mineral pyroxene and the clear white areas are the mineral plagioclase. These are the two most abundant minerals in basalt, both on Earth and Mars. The black areas are magnetite, an iron-oxide mineral. Photograph by Allan Treiman, Lunar and Planetary Institute

This microscopic view, 2.3 millimeters across, is in false color, produced by holding polarizing filters above and below the microscopic slide. These filters cause different minerals to have distinctive colors, allowing easy identification of the minerals. Most of this meteorite (in yellow, green, pink, and black) is the mineral olivine, which is common in some basaltic rocks. The striped grain near the center is the mineral pyroxene. Photograph by Allan Treiman, Lunar and Planetary Institute

This microscopic view of another martian meteorite shows the real colors of the mineral grains in the meteorite. The clear and cracked areas are the minerals olivine and pyroxene. The reddish and black veinlets and patches are clay and rust where the pyroxene and olivine reacted with liquid water. These veinlets of clay and rust are truncated by the the meteorite's fusion crust, which formed when the meteorite came through the Earth's atmosphere. The veinlets therefore must have formed before the meteorite came to Earth; it is most likely that the veinlets formed from water on Mars. Photograph by Allan Treiman, Lunar and Planetary Institute

This year, Mars became a major focal point for people around the world as it made its closest approach to Earth in 60,000 years. These “close” approaches are known as perihelic oppositions.

To put it more simply, the the fact that not only are Mars and Earth are in a “direct line of sight,” the planes of their orbits are slightly tilted, creating optimum viewing conditions

By early 2004, there will be seven spacecraft at Mars, sent by nations around the world.