01.06.2017 Earth and Its Moon, as Seen From Mars
11.15.2016 Schiaparelli Impact Site on Mars, Stereo
11.03.2016 Schiaparelli Impact Site on Mars, in Color
03.30.2016 Erisa Hines
03.30.2016 Buzz Aldrin
03.21.2016 For a Decade Orbiting Mars: One Recent View
03.09.2016 For a Decade Orbiting Mars: One Recent View
03.09.2016 Mars Reconnaissance Orbiter By the Numbers
03.01.2016 MRO sees Frosty Spring Slopes
02.12.2016 Women in Science
02.10.2016 Wind at Work
11.16.2015 Change Observed in Martian Sand Dune
10.05.2015 'The Martian' Story's Ares 4 Landing Site
10.05.2015 The Ares 3 Landing Site (Figure A)
09.30.2015 Avalanche Ho!
06.29.2015 Mars Exploration Zone Layout Considerations
06.17.2015 Active High-Latitude Dune Gullies
06.03.2015 Crisp Crater in Sirenum Fossae
05.20.2015 Sedimentary Rock Layers on a Crater Floor
05.20.2015 Honey, I Shrunk the Mesas
05.11.2015 Icy Wonderland
05.04.2015 Diverse Orbits Around Mars
03.27.2015 South Pole Spiders
03.27.2015 A Smile a Day....
03.25.2015 Pitted Landforms in Southern Hellas Planitia
03.12.2015 Curiosity Heading Away from 'Pahrump Hills'
02.18.2015 Lava Flow Near the Base of Olympus Mons
02.09.2015 Yardangs in Arsinoes Chaos, Mars
02.04.2015 Curiosity Rover at 'Pahrump Hills'
01.22.2015 Frost on Crater Slope
01.16.2015 Components of Beagle 2 Flight System on Mars
12.03.2014 An Enigmatic Feature in Athabasca Lava Flows
12.02.2014 NASA's Journey to Mars
11.07.2014 Mars Orbiter Sizes Up Passing Comet
10.19.2014 Siding Spring Mars Spacecraft
Martian Features Formed When Material Moves DownslopeAs on the Earth, many processes can move material down a Martian slope. This graphic compares seven different types of features observed on Mars that appear to result from material flowing or sliding or rolling down slopes.
Processes that explain one type of downslope feature may be irrelevant to another type. Some processes depend on the presence of a fluid, some are driven by seasonal changes in the environment, and others occur randomly when gravity is able to pull down unstable slope material.
These different processes can generate a wide range of feature shapes, though sometimes different processes can yield similar-looking results. Thus, to figure out how a feature may have formed, more must be considered than its shape. For example, researchers examining images from Mars orbiters have found differences in 1. the season when the features are formed or are active (e.g., the features called "recurring slope lineae" or RSLs appear during late spring and summer, but linear gullies are active only during early spring); 2. the features' sizes (e.g., slope streaks can extend for miles or kilometers, but dark frost streaks on dunes extend only up to 100 yards, or meters); and 3. the types of terrain on which a feature is found (e.g., gullies with an alcove-channel-apron shape are found both on rocky slopes and on sandy slopes, but linear gullies are only found on sandy slopes; dark frost streaks are formed on frozen dune slopes, but RSLs are formed on dark, warm slopes).
Scientists consider all of these factors -- and more -- when trying to form a complete picture about a feature's formation history and in figuring out what the presence of that feature means about the environment.
The seven images of different types of downslope features come from three different NASA Mars orbiters. The image of a landslide comes from the Thermal Emission Imaging System (THEMIS) on NASA's Mars Odyssey. The images of alcove-channel-apron gullies and of slope streaks come from the Mars Orbiter Camera (MOC) in NASA's Mars Global Surveyor. The other images come from the High Resolution Imaging Science Experiment (HiRISE) on NASA's Mars Reconnaissance Orbiter.
The University of Arizona, Tucson, operates THEMIS. Malin Space Science Systems, San Diego, operated MOC. The University of Arizona, Tucson, operates HiRISE. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, has managed the Mars orbiter projects for NASA's Science Mission Directorate, Washington.
Image Credit: NASA/JPL-Caltech/ASA/MSSS/UA