The Solar System:
Weather, climate, and the atmosphere
Atmospheric composition of Mars (from left to right: carbon dioxide, argon, molecular nitrogen, molecular oxygen, carbon monoxide). Even though Mars’ atmosphere is almost completely composed of a strong greenhouse gas, it is too thin to keep Mars warm. The atmosphere of Mars is about 100 times less dense than Earth’s atmosphere, giving a pressure of only 0.6% that of Earth's atmosphere at sea level. There is too little pressure and oxygen in Mars' atmosphere support human life.Credit: Melikamp (Wikimedia Commons), CC BY SA 3.0 [link]; based on public domain data from NASA/JPL-Caltech, SAM/GSFC [link]
Dust storms on Mars
Two 2001 images from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter show a dramatic change in the planet's appearance when haze raised by dust-storm activity in the south became globally distributed.Credit (image and some text): NASA/JPL-Caltech/MSSS [link]
The winds in a Martian dust storm blow as fast as the winds of a Category 1 hurricane (average wind speed 74-95 mph). On Earth, that’s enough to knock a person over. But on Mars it would feel like a light breeze.
Effect of wind on the sand under Curiosity while it was parked for a day. The pair of images in this animation shows effects of one Martian day of wind blowing sand underneath NASA's Curiosity Mars rover on a non-driving day for the rover. Each of the two images was obtained just after sundown a day apart in January 2017 by the rover's downward-looking Mars Descent Imager (MARDI). The area of ground shown in the images spans about 3 feet (about 1 meter) left-to-right.
A dust devil spins across the surface of Gusev Crater just before noon on Mars. NASA's Spirit rover took the series of images in this 21-frame animation with its navigation camera on the rover's martian day, or sol, 486 (15 May 2005). The event occurred during a period of 9 minutes and 35 seconds, with the dust devil's progressing in a northeasterly direction about 1.0 kilometer (0.62 mile) away from Spirit. The whirlwind was traveling at about 4.8 meters per second (16 feet per second) and covered a distance of about 1.6 kilometers (1 mile). Contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil. The dust devil is about 34 meters (112 feet) in diameter.Credit (image and some text): NASA/JPL [link]
A towering dust devil casts a serpentine shadow over the Martian surface in this image acquired by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. The devil is 800 meters in height and 30 meters wide. The scene is a late-spring afternoon in the Amazonis Planitia region of northern Mars. The view covers an area about four-tenths of a mile (644 meters) across. North is toward the top.Credit (image and some text): NASA/JPL-Caltech/University of Arizona) [link]
Dust storm with water ice clouds (2009). This image shows a turbulent mass of thick, roiling, red Martian dust rising from a network of canyons and flowing diagonally toward the lower left corner of the frame. Above the storm front, wispy, white clouds of water ice are present.Credit (image and some text): NASA/JPL-Caltech [link]
How did Mars lose (most of) its atmosphere?
Mars' atmosphere loss is still ongoing. This figure shows three views of the escaping atmosphere, obtained by MAVEN's Imaging Ultraviolet Spectrograph, are shown here. By observing all of the products of water and carbon dioxide breakdown, MAVEN's remote sensing team can characterize the processes that drive atmospheric loss on Mars. These processes may have transformed the planet from an early Earthlike climate to the cold and dry climate of today. MAVEN is NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft.Credit: NASA/University of Colorado [link]
Seasons and the polar ice caps on Mars
North pole winter
South pole summer
North pole summer
South pole winter
These images show the polar ice caps of Mars during different seasons. Just like on Earth, when it is summer at the north pole, it is winter at the south pole, and vice-versa.Credit: NASA/JPL/MSSS [link]
This detailed image of the south polar ice cap of Mars was obtained by ESA’s Mars Express, which has been exploring and imaging the martian surface and atmosphere since 2003. We may be used to seeing numerous images of red and brown-hued soil and ruddy landscapes peppered with craters, but the Red Planet isn’t always so red.Credit (image and some text): ESA/DLR/FU Berlin/Bill Dunford [link]