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2001 Mars Odyssey
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Hills abound in this portion of Mars located in the Vastitas Borealis region of the high northern plains. These hills are part of Scandia Colles. Note that some of the hills have aprons surrounding them. The northern part of Milankovic crater is visible in the lower portion of this image.
Bumpy Terrain in Vastitas Borealis
Full Resolution
This THEMIS image of rounded hills and ridges in Arcadia Planitia shows a very intriguing geomorphic feature that may be attributed to the presence of an icy-rock mixture of material. Smooth aprons of material are observed to be preferentially located on the cold, north facing slopes of hills and extend further and beyond the deposits located on other sides. These smooth deposits are in stark contrast to the more rough surfaces that dominate the scene and it has been suggested that they represent a preserved mixture of ice and rock. How exactly this deposit forms still remains a mystery. They may have been "pasted" onto the slopes and preserved on the cold facing sides or they may represent the result of downslope motion of material that is enhanced by the presence of ground ice. In either case, this interesting observation suggests that ground ice may still play an important role in the formation and preservation of martian surface features.
Arcadia Planitia
Full Resolution
This THEMIS visible image shows a close-up view of the ridged plains in Hesperia Planum. This region is the classic locality for martian surfaces that formed in the "middle ages" of martian history. The absolute age of these surfaces is not well known. However, using the abundance of impact craters, it is possible to determine that the Hesperian plains are younger than the ancient cratered terrains that dominate the southern hemisphere, and are older than low-lying plains of the northern hemisphere. In this image it is possible to see that this surface has a large number of 1-3 km diameter craters, indicating that this region is indeed very old and has subjected to a long period of bombardment. A large (80 km diameter) crater occurs just to the north (above) this image. The material that was thrown out onto the surface when the crater was formed ("crater ejecta") can be seen at the top of the THEMIS image. This ejecta material has been heavily eroded and modified since its formation, but there are hints of lobate flow features within the ejecta. Lobate ejecta deposits are thought to indicate that ice was present beneath the surface when the crater was formed, leading to these unusual lobate features. Many of the Hesperian plains are characterized by ridged surfaces. These ridges can be easily seen in the MOLA context image, and several can be seen cutting across the lower portion of the THEMIS image. These "wrinkle" ridges are thought to be the result of compression (squeezing) of the lavas that form these plains.
Hesperia Planum
Full Resolution
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Cross-section of Icy Soil
Full Resolution
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Polar Maps of Thermal and Epithermal Neutrons
Full Resolution
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Global Map of Thermal Neutrons
Full Resolution
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Global map of epithermal neutrons
Full Resolution
This lunar-like scene occurs along the southeastern rim of the Isidis Planitia basin. The Isidis basin is an ancient impact crater some 1200 km across that is found along the boundary separating the heavily-cratered southern highland terrain of Mars from the northern lowlands. Elements of both terrains are evident in this image as an island of rugged highland terrain surrounded by smoother lowland terrain. The resurfacing of the Isidis basin produced a system of wrinkle ridges, some of which are seen on the lowland terrain in the image. Wrinkle ridges are a common feature on the surface of the moon and add to the lunar-like quality of this image. Layers are visible in the large island, the most resistant of which likely are from lava flows that created the highland terrain. The process by which the global-scale highland/lowland dichotomy was created remains a mystery.
Isidis Rim
Full Resolution
This image is near the southern edge of a low, broad volcanic feature called Syrtis Major. A close look at this image reveals a wrinkly texture that indicates a very rough surface that is associated with the lava flows that cover this region. On a larger scale, there are numerous bright streaks that trail topographic features such as craters. These bright streaks are in the wind shadows of the craters where dust that settles onto the surface is not as easily scoured away. It is important to note that these streaks are only bright in a relative sense to the surrounding image. Syrtis Major is one of the darkest regions on Mars and it is as dark as fresh basalt flows or dunes are on Earth.
Syrtis Major
Full Resolution
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First THEMIS Image of Mars
Full Resolution
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