MOLA colorized relief map of Amazonis Planitia. Colors indicate elevation, with red highest, yellow intermediate, and green/blue lowest.
Amazonis Planitia is one of the smoothest plains on Mars. It is located between the Tharsis and Elysium volcanic provinces, to the west of Olympus Mons, in the Amazonis and Memnonia quadrangles, centered at . The plain's topography exhibits extremely smooth features at several different lengths of scale. A large part of the Medusae Fossae Formation lies in Amazonis Planitia.
Age and composition
Only approximately 100 million years old, these plains provide some of the fewest sedimentary layers impeding viewing of the Martian terrain, and closely resemble the composition of Earth's Iceland. Formed by free-flowing lava across great plains, Amazonis has been described by William Hartmann as a "bright dusty volcanic desert crossed by many fresh-looking lava flows."
Amazonis has become the primary focus of modern research efforts both because of its geological composition and because of its relative youth compared to other Martian regions, which are often hundreds of millions of years older. Hartman writes that the plain closely resembles Iceland's surface, with its "strange cobweb-like networks of ridges and crags [on both planets, divide] smoother areas into a pattern something like fragments of a broken plate." Both land masses' shapes have been formed by lava flows from volcanic eruptions, causing both surfaces to be covered by a thick layer of hardened lava. Findings from aerial footage of both Amazonis and Iceland have shown nearly identical terrain patterns, signifying the comparative ages of the two regions.
Ironically, the entire contemporary era on Mars has been named the Amazonian Epoch because researchers originally (and incorrectly) thought Amazonis Planitia to be representative of all Martian plains. Instead, over the past two decades, researchers have realized that the area's youth and extremely smooth surface actually distinguish the area from its neighbors. It is even possible that the area possessed distinctive characteristics when all of Mars was under water.
Although the full implications of Amazonis's youth have not yet been determined, the nature of the area (i.e. lack of sedimentary rock) has at least provided researchers evidence that the areas are the most likely to provide future discoveries, and as such, has been proposed as a future site for most NASA landings.
Medusae Fossae Formation
The Medusae Fossae Formation is a soft, easily eroded deposit that extends for nearly 1,000 km along the equator of Mars. The surface of the formation has been eroded by the wind into a series of linear ridges called yardangs. These ridges generally point in direction of the prevailing winds that carved them and demonstrate the erosive power of Martian winds. The easily eroded nature of the Medusae Fossae Formation suggests that it is composed of weakly cemented particles,
Yardangs, as seen by HiRISE under HiWish program Location is near Gordii Dorsum in the Amazonis quadrangle.
Yardangs near a crater, as seen by HiRISE under HiWish program Location is in the Amazonis quadrangle.
Linear ridge networks
Linear ridge networks are found in various places on Mars in and around craters. Ridges often appear as mostly straight segments that intersect in a lattice-like manner. They are hundreds of meters long, tens of meters high, and several meters wide. It is thought that impacts created fractures in the surface, these fractures later acted as channels for fluids. Fluids cemented the structures. With the passage of time, surrounding material was eroded away, thereby leaving hard ridges behind. Since the ridges occur in locations with clay, these formations could serve as a marker for clay which requires water for its formation. Water here could have supported past life in these locations. Clay may also preserve fossils or other traces of past life.
When a fluid moves by a feature like a mound, it will become streamlined. Often flowing water makes the shape and later lava flows spread over the region. In the pictures below this has occurred.
Layers in Gordii Dorsum Region, as seen by HiRISE under HiWish program. Dark lines are Dark Slope Streaks.
Dark slope streaks on mesa, as seen by HiRISE under HiWish program Location is Amazonis quadrangle.
More Images from Amazonis Planitia
- Amazonian (Mars)
- Dark slope streaks
- Geography of Mars
- List of plains on Mars
- Medusae Fossae Formation
- E. R. Fuller and J. W. Head, III, "GEOLOGIC HISTORY OF THE SMOOTHEST PLAINS ON MARS (AMAZONIS PLANITIA) AND ASTROBIOLOGICAL IMPLICATIONS." Lunar and Planetary Science XXXIII (2002). URL accessed 19 April 2006.
- Hartmann, William. A Traveler's Guide to Mars: The Mysterious Landscapes of the Red Planet. Workman Publishing: New York, 2003.
- Hartmann, 275.
- Hartmann, 286.
- Fuller, E.R. and J.W. Head III (2002), Amazonis Planitia: The role of geologically recent volcanism and sedimentation in the formation of the smoothest plains on Mars.
- Hartmann, 287.
- Grotzinger, J. and R. Milliken (eds.) 2012. Sedimentary Geology of Mars. SEPM
- Head, J., J. Mustard. 2006. Breccia dikes and crater-related faults in impact craters on Mars: Erosion and exposure on the floor of a crater 75 km in diameter at the dichotomy boundary, Meteorit. Planet Science: 41, 1675-1690.
- Mangold et al. 2007. Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 2. Aqueous alteration of the crust. J. Geophys. Res., 112, doi:10.1029/2006JE002835.
- Mustard et al., 2007. Mineralogy of the Nili Fossae region with OMEGA/Mars Express data: 1. Ancient impact melt in the Isidis Basin and implications for the transition from the Noachian to Hesperian, J. Geophys. Res., 112.
- Mustard et al., 2009. Composition, Morphology, and Stratigraphy of Noachian Crust around the Isidis Basin, J. Geophys. Res., 114, doi:10.1029/2009JE003349.
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