Swiss Cheese and Dust Devils: 7 High-Resolution Shots of Surface Activity on Mars [Slide Show]
The Red Planet is frigid and possibly sterile, but its surface still sees plenty of action
![Swiss Cheese and Dust Devils: 7 High-Resolution Shots of Surface Activity on Mars [Slide Show]](https://static.scientificamerican.com/sciam/cache/file/C68C39AD-1038-45B9-B5D3EFD2ECCDEF5F.jpg?w=590&h=393)
Swiss Cheese and Dust Devils: 7 High-Resolution Shots of Surface Activity on Mars [Slide Show]
- SPILLAGE: Before HiRISE scientists discovered recurring slope lineae in 2011 Martian gullies were perhaps the most convincing evidence for flowing liquid water on the Red Planet. The photograph above, taken in 2010, highlights in blue the areas within one system of gullies where surface material has eroded away or been deposited in the preceding year. The flow pattern resembles that of liquid, but a 2012 study suggested that changes within gullies may arise from the presence of dry ice rather than water. NASA/JPL/University of Arizona
- HOLE PUNCH: Mars’s surface is arid, for the most part, but just belowground lie stores of water ice. HiRISE has photographed numerous fresh craters, such as this 20-meter-wide basin, which have exposed and ejected ice from the subsurface. The bright ejecta fades away over months or years as the ice sublimates into water vapor. NASA/JPL/University of Arizona
- TWISTER: The HiRISE camera snapped this shot of a towering dust devil crossing the northern hemisphere’s Amazonis Planitia in March 2012. By measuring the dust devil’s shadow and the angle of solar illumination, planetary scientists determined that the structure is some 20 kilometers tall, including the loose dust clouds atop the twister. The core column of spinning dust alone is roughly half that height. NASA/JPL/University of Arizona
- QUICKSAND: The HiRISE camera snapped this photo of sand dunes in Nili Patera, an ancient volcanic caldera near the Martian equator, in 2012. That same year a group of researchers published a study in Natureshowing that the windblown Nili Patera dunes advance rapidly, at rates comparable to Earthly sand dunes in Antarctica. That finding came as a surprise, given that Mars’s thin atmosphere should be less efficient than Earth’s at pushing large masses of sand across the surface. (Scientific American is part of Nature Publishing Group.) NASA/JPL/University of Arizona
- HOLEY CAP: Mars’s south pole features an ice cap composed of both water ice and frozen carbon dioxide. In some places patches of carbon dioxide have sublimated into gas and escaped into the atmosphere, leaving behind odd-shaped depressions that lend such regions their colloquial description: “Swiss cheese terrain.” The Mars Reconnaissance Orbiter and its predecessors have documented rapid changes in these Swiss cheese depressions, some of which expand by a few meters per Martian year. NASA/JPL/University of Arizona
- STREAKERS: Another animated gif of Newton Crater shows more RSL popping up in the southern hemisphere’s warmer seasons. The dark RSL are most prominent in the fourth frame of the gif (labeled “ESP_022689_1380”), taken during early to mid-summer, toward the top of the photograph. NASA/JPL/University of Arizona
- TRICKLE-DOWN: This enhanced-color animated gif shows recurring slope lineae (RSL) inside Newton Crater on Mars, as photographed over time by the HiRISE camera onboard NASA’s Mars Reconnaissance Orbiter. Around summertime RSL appear on steep slopes in the southern crater, grow longer and then fade as autumn approaches. The key in the upper left shows the seasonal progression of the images; the first frame of the gif, largely devoid of RSL, was taken at the beginning of southern spring on Mars. The subsequent frames, from the following Martian year, show the growth of RSL during southern summer. The dark, streaky RSL are most prominent in the fourth frame (labeled “ESP_022689_1380”), taken during early to mid-summer. Planetary scientists have not conclusively determined what produces RSL on Mars, but sun-warmed ice melting into liquid brines is a compelling possibility. NASA/JPL/University of Arizona
