Mars - Overview

September 9, 2010, 2:47 pm
Source: NASA: Solar System Exploration - Mars
Content Cover Image

Mars is a small rocky body once thought to be very Earth-like. Like the other "terrestrial" planets - Mercury, Venus, and Earth - its surface has been changed by volcanism, impacts from other bodies, movements of its crust, and atmospheric effects such as dust storms. It has polar ice caps that grow and recede with the change of seasons; areas of layered soils near the Martian poles suggest that the planet's climate has changed more than once, perhaps caused by a regular change in the planet's orbit. Martian tectonism - the formation and change of a planet's crust - differs from Earth's. Where Earth tectonics involve sliding plates that grind against each other or spread apart in the seafloors, Martian tectonics seem to be vertical, with hot lava pushing upwards through the crust to the surface. Periodically, great dust storms engulf the entire planet. The effects of these storms are dramatic, including giant dunes, wind streaks, and wind-carved features.  Image: "Hubble's Closest View of Mars – August 27, 2003."

Scientists believe that 3.5 billion years ago, Mars experienced the largest known floods in the solar system. This water may even have pooled into lakes or shallow oceans. But where did the ancient flood water come from, how long did it last, and where did it go?

In May 2002, scientists announced the discovery of a key piece in the puzzle: the Mars Odyssey spacecraft had detected large quantities of water ice close to the surface – enough to fill Lake Michigan twice over. The ice is mixed into the soil only a meter (about 3 feet) below the surface of a wide area near the Martian south pole.

Many questions remain. At present, Mars is too cold and its atmosphere is too thin to allow liquid water to exist at the surface for long. More water exists frozen in the polar ice caps, and enough water exists to form ice clouds, but the quantity of water required to carve Mars' great channels and flood plains is not evident on - or near - the surface today. Images from NASA's Mars Global Surveyor spacecraft suggest that underground reserves of water may break through the surface as springs. The answers may lie deep beneath Mars' red soil.

A panoramic view of Mars captured by the Pathfinder lander in 1997.
A panoramic view of Mars captured by the Pathfinder lander in 1997. (Source: NASA.)

Unraveling the story of water on Mars is important to unlocking its past climate history, which will help us understand the evolution of all planets, including our own. Water is also believed to be a central ingredient for the initiation of life; the evidence of past or present water on Mars is expected to hold clues about past or present life on Mars, as well as the potential for life elsewhere in the universe. And, before humans can safely go to Mars, we need to know much more about the planet's environment, including the availability of resources such as water.

Mars has some remarkable geological characteristics, including the largest volcanic mountain in the solar system, Olympus Mons (27 km high and 600 km across); volcanoes in the northern Tharsis region that are so huge they deform the planet's roundness; and a gigantic equatorial rift valley, the Valles Marineris. This canyon system stretches a distance equivalent to the distance from New York to Los Angeles; Arizona's Grand Canyon could easily fit into one of the side canyons of this great chasm.

Mars also has two small moons, Phobos and Deimos. Although no one knows how they formed, they may be asteroids snared by Mars' gravity.

Two Faces of Mars

Click to view full-size image.
2003 Mars Closest Approach.  (Source:


Mars Atlas

In 1979, NASA published ATLAS OF MARS: THE 1:5,000,000 MAP SERIES, edited by R.M. Batson, P.M. Bridges, and J.L. Inge, of the U.S. Geological Survey in Flagstaff, Arizona. The Atlas is a compendium of airbrushed shaded relief maps, controlled photomosaics, and in a few cases albedo (shading) maps, mostly assembled from Mariner 9 survey images, with some gaps filled by Viking orbiter images. The planet was divided into thirty "quadrangles" or areas, each with an "Mars Chart" or "MC" number (MC-1 through MC-30). The equatorial region was portrayed in the Mercator projection, with Lambert Conformal Conic for the mid-latitudes and Polar Stereographic for the poles.  The Mars Atlas is displayed below, and can be viewed by visitng the Mars Atlas.

Mars Atlas
Mars Atlas (Source: NASA-JPL.)

Although digital products such as the Mars Digital Image Mosaic (MDIM) and various Mars Global Surveyor (MGS) Mars Orbiter Laser Altimeter (MOLA) maps have partially supplanted the ATLAS, it remains a standard desktop reference today.

Mars Global Camera Global Mosaic

In 1999, the Mars Orbiter Camera (MOC) aboard the MGS orbiter acquired a global stereo image dataset using its red-filter Wide Angle Camera. We have recently completed a 256 pixel/degree (about 230 meters/pixel) mosaic of these images using software developed at Malin Space Science Systems (MSSS). To access both partial and full-resolution mosaics in Planetary Data System format, click the image below or visit Mars MOSAIC. 

Click image for full-size view.
The image above is a reproduction of the new MGS MOC Mars Digital Map.
(Images Credit: NASA/JPL/Malin Space Science Systems.)

The image above is a reproduction of the new MGS MOC Mars Digital Map. By clicking on the various sections (quadrangles) of the map, one can access the atlas at two resolutions: first a browse image at about 6 km/pixel, and by clicking on that browse image, at a resolution of about 1 kilometer per pixel (~0.62 miles per pixel). Each quadrangle is independently contrast-enhanced and labeled with a 5-degree grid. This is the first of several cartographic products that MSSS expects to release this year.  The index map can be viewed at full resolution by clicking here.

External Links

 Click link below for more details.  



(2010). Mars - Overview. Retrieved from


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