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Goals: Mission Results

Goal 2: Characterize the Climate of Mars

Today, liquid water is not found on the surface of Mars because the planet is too cold and the atmospheric pressure too low. Yet, not only the Mars rovers, but earlier missions such as NASA's Mars Global Surveyor orbiter and the Pathfinder lander and Sojourner rover, found evidence suggesting that Mars was once a wetter place. Some scientists think Mars used to be warmer. Others think Mars has always been a cold place by Earth standards, but that frozen water melts periodically when the planet's poles are tilted more directly toward the Sun. Some think volcanic activity may occasionally melt polar ice or ice buried beneath the surface.

This striking color panorama shows undulating waves of reddish-brown dunes marching across a sandy floor from left to right. The left-facing, shallower flanks of the dunes are bathed in sunlight. The right, steeper faces are in shadow. In the foreground, at the bottom of the image, the dunes thin out as their outermost tendrils near the slopes of the inside walls of Endurance Crater. Toward the top of the image, the dunes become more and more complex, zigzagging suddenly from left to right and eventually interlocking with the crests of other dunes to form an irregular framework of sharply scalloped ridges interspersed with low-lying, sand-filled depressions.
Wind-Swept Planet

Modern Mars is a vast desert of sand dunes, ripples, dust devils, and streaks of materials deposited by wind. Dust even covers icy deposits at the poles. But the surface of the Red Planet has been wet at times. Both Mars rovers as well as orbiters have found plenty of evidence for water in the past. Opportunity used the 13-filter panoramic camera to acquire this color image of dunes marching across the floor of Endurance Crater.

Credit: NASA/JPL-Caltech/Cornell

If life could ever have existed on the surface of Mars, it would have had to be able to survive the planet's climate. Both Mars Exploration Rovers have collected a treasure trove of data about the Martian atmosphere to help characterize the modern climate on the red planet. This information is important because atmospheric conditions affect the amount of sunlight reaching the surface and the amount of heat reflected back into space.

This pair of black-and-white images shows two views of a black peg taken at different times of day. The peg sticks up from the middle of a small square plate bearing three concentric circles of different colors. On the left, the peg is grayish-white, covered with a veneer of frost. On the right, the peg is black after the frost has melted.
Frost on Mars

In October 2004, the Opportunity rover documented a thin veneer of frost coating a black peg that serves as a calibration target for the panoramic camera.

Credit: NASA/JPL-Caltech/Cornell


Spirit and Opportunity surveyed the amount and distribution of dust and water ice in the Martian atmosphere, using cameras and spectrometers that measured the absorption of different wavelengths of light. As the seasons changed from summer to fall to winter to spring, the rovers monitored changes in temperature at different heights above the surface and at different times of day.

This panoramic mosaic of black-and-white images shows wispy, white clouds above the promontory of Burns Cliff.
Clouds Accompany Martian Winter

In November, 2004, Opportunity observed clouds at the onset of Martian winter. Similar in appearance to cirrus clouds on Earth, these clouds are believed to be composed of water-ice particles on the order of several micrometers (a few ten-thousandths of an inch) in length.

Credit: NASA/JPL-Caltech


The rovers have provided daily weather reports from Mars. Spirit documented dozens of daily dust devils during the Martian spring. On the opposite side of Mars, Opportunity took images of clouds in the Martian sky and frost on the rover deck. These observations are giving researchers a better understanding of current climate conditions on Mars, an important step in determining how they may or may not be different from those in the past.

This black-and-white image shows a swirling cloud of whitish dust and debris wheeling across a flat expanse of sand. The horizon is also flat where it meets a gray sky.
Dust Devils on Mars

During spring and summer of 2005 on Earth, Spirit often observed dozens of dust devils each day at around lunchtime local solar time on Mars.

Credit: NASA/JPL-Caltech


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