The Arizona State University TES Team

The Mars Global Surveyor began mapping Mars in 1999. The Thermal Emission Spectrometer instrument on board Surveyor maps the temperature and, hence, the amount of dust in the atmosphere. Beginning in mid-June, 2001, a region of increased dust abundance appeared in the Hellas Basin, an impact basin in the southern uplands that is about 1,800 kilometers in diameter and 6 kilometers deep. This continued for two weeks when the storm intensified and expanded. This is the largest storm Surveyor has seen since it began mapping the planet.

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Effects of dust storms on Mars

A dust storm of this magnitude has significant impact on the Martian climate. Dust in the atmosphere is warmed by the Sun and heats the atmosphere by 20° C. This warm air rises and moves into the Northern Hemisphere, warming the Northern Hemisphere and causing planet-wide climate variability.

Ellen Cohen

Phil James (University of Toledo), Todd Clancy (STScI), Steven Lee (University of Colorado), and NASA/STScI

These images appear to have been taken from above the Martian pole, but they were taken with the Hubble Space Telescope from Earth orbit. Each frame in this animation was constructed from three separate images taken in October 1996 and in January and March of 1997. The first image corresponds to early spring in the Northern Hemisphere when the polar ice cap extends to about 60° north latitude. The second image was taken in mid-spring and shows a smaller ice cap resulting from increasing atmospheric warming. The final image from early summer on Mars shows a vastly reduced polar cap; much of the carbon dioxide ice has sublimated, revealing the terrain beneath.

Martian Seasons

Mars has a cycle of seasons that is similar to Earth. The reason for this is that both planets are similarly tilted on their rotational axes: a 23.5° tilt for Earth and a 25.2° tilt for Mars. Because Mars takes about twice as long to orbit the Sun, each Martian season is about twice as long as the corresponding season on Earth. In addition, the Martian atmosphere is much thinner than Earth's atmosphere, so there is little insulation to protect the Martian atmosphere from temperature shifts due to changes on the surface or in the Mars-Sun distance.

The Mars-Sun distance

The Mars-Sun distance changes by 20 percent over the course of the year. When Mars is closest to the Sun, it is summer in the Southern Hemisphere and temperatures are up 35° F, producing dust storms that swirl around the planet and absorb sunlight, further heating the atmosphere. When Mars is farthest from the Sun, water-ice clouds reduce atmospheric temperatures. The dust particles in the atmosphere seed these clouds, then fall to the ground. Competition between cloud cooling and dust heating drives annual as well as short-term climate changes on Mars.

Ellen Cohen

NASA/JPL-CalTech

This animation shows the terrain of Mars as the planet rotates. The data were taken using the Mars Orbiter Laser Altimeter (MOLA) onboard the Mars Global Surveyor. The instrument transmits infrared laser pulses to the Martian surface and measures the time of flight to compute the range of the spacecraft to the surface. These measurements are then used to construct a precise topographic map of Mars.

The Martian Terrain

The information from MOLA gives scientists some of the most detailed information about the surface of Mars. The first pictures of the surface from space came in 1965 from the Mariner 4 spacecraft. In the 1970s, the Viking spacecraft landed on the surface and returned detailed information about the soil composition. Mars is divided into two main types of terrain: ancient cratered areas and younger, volcanic regions. Ancient cratered terrain is found mainly in the southern hemisphere. The volcanic plains are mainly in the northern hemisphere and lie several kilometers below the southern uplands. Mars has the largest volcano in the Solar System, Olympus Mons, which is 25 kilometers above the surrounding plains and 500 kilometers in diameter. Mars also has runoff channels, where the runoff of ancient rainstorms once flowed.

The Mars-Sun distance

The Mars-Sun distance changes by 20 percent over the course of the year. When Mars is closest to the Sun, it is summer in the Southern Hemisphere and temperatures are up 35° F, producing dust storms that swirl around the planet and absorb sunlight, further heating the atmosphere. When Mars is farthest from the Sun, water-ice clouds reduce atmospheric temperatures. The dust particles in the atmosphere seed these clouds, then fall to the ground. Competition between cloud cooling and dust heating drives annual as well as short-term climate changes on Mars.

Ellen Cohen