Amazonis Planitia

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."Hartmann, William. A Traveler's Guide to Mars: The Mysterious Landscapes of the Red Planet. Workman Publishing: New York, 2003.

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.Hartmann, 275. 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.Hartmann, 286.

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.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.

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.Hartmann, 287.

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,Grotzinger, J. and R. Milliken (eds.) 2012. Sedimentary Geology of Mars. SEPM

Image:Medusae Fossae Remnant.jpg|Plateau made up of Medusae Fossae materials and rootless cones, as seen by HiRISE.

WikiESP 035558 1830yardang.jpg|Yardangs, as seen by HiRISE under HiWish program Location is near Gordii Dorsum in the Amazonis quadrangle.

WikiESP 036429 1925yardangscrater.jpg|Yardangs near a crater, as seen by HiRISE under HiWish program Location is in the Amazonis quadrangle.

Linear ridge networks are found in various places on Mars in and around craters.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. 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.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. Water here could have supported past life in these locations. Clay may also preserve fossils or other traces of past life.

Image:26552sharpridges.jpg|Narrow ridges, as seen by HiRISE under HiWish program. The ridges may be the result of impacts fracturing the surface.

ESP 036745 1905top.jpg|Linear ridge networks, as seen by HiRISE under HiWish program

36745 1905lridgesshort.jpg|Close-up of ridge network, as seen by HiRISE under HiWish program This is an enlargement of a previous image.

36745 1905ridgesx.jpg|Close-up of ridge network, as seen by HiRISE under HiWish program This is an enlargement of a previous image.

ESP 036745 1905ridges.jpg|Linear ridge networks, as seen by HiRISE under HiWish program

ESP 047611 1915polygons.jpg|Wide view of polygon ridges, as seen by HiRISE under HiWish program

47611 1915ridgesclose.jpg|Polygonal ridges, as seen by HiRISE under HiWish program

47611 1915ridgescloseshadows.jpg|Polygonal ridges, as seen by HiRISE under HiWish program

47611 1915ridgesstreaks.jpg|Polygonal ridges, as seen by HiRISE under HiWish program

47611 1915ridgessuperclose.jpg|Close view of polygonal ridges, as seen by HiRISE under HiWish program

ESP 047611 1915closecolor.jpg|Close, color view of polygonal ridges, as seen by HiRISE under HiWish program

File:ESP 054850 1900ridges.jpg|Wide view of large ridge network, as seen by HiRISE under HiWish program

File:54850 1900ridges.jpg|Close view of ridge network, as seen by HiRISE under HiWish program Box shows size of football field.

File:54850 1900ridgesclosecolor.jpg|Close, color view of ridges, as seen by HiRISE under HiWish program

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.

ESP 045133 1970lava.jpg|Wide view of streamlined shape and rafts of lava, as seen by HiRISE under HiWish program

45133 1970lavascalebottom.jpg|Closer view of previous image, showing layers, as seen by HiRISE under HiWish program

45133 1970lvarafts.jpg|Close view of lava rafts from previous images, as seen by HiRISE under HiWish program

Image:Marte Vallis Island.JPG|Streamlined Island in Marte Vallis, as seen by HiRISE. Click on image for good view of Dark Slope Streaks. Island is just to the west of Pettit Crater. Scale bar is 500 meters long.

Image:ESP 035480 2015streamlined.jpg|Streamlined shape showing layers, as seen by HiRISE under HiWish program.

ESP 048640 2100lavasurface.jpg|Lava flows affected by obstacles, as seen by HiRISE under HiWish program Arrows show two obstacles that are changing the flow.

48640 2100lavasurfacescaled.jpg|View of a lava lobe, as seen by HiRISE under HiWish program The box shows the size of a football field.

48640 2100lavasurfacescaledclose.jpg|Close view of a lava lobe, as seen by HiRISE under HiWish program The box shows the size of a football field.

Many places on Mars show dark streaks on steep slopes, such as crater walls. It seems that the youngest streaks are dark and they become lighter with age. Often they begin as a small narrow spot then widen and extend downhill for hundreds of meters. Several ideas have been advanced to explain the streaks. Some involve water,http://www.space.com/scienceastronomy/streaks_mars_021200.html{{dead link|date=December 2016 |bot=InternetArchiveBot |fix-attempted=yes }} or even the growth of organisms.{{cite web|url=http://www.spcae.com/scienceastronomy/streaks_mars_021211.html |title=Archived copy |access-date=2010-12-19 |url-status=dead |archive-url=https://web.archive.org/web/20150221231430/http://www.spcae.com/scienceastronomy/streaks_mars_021211.html |archive-date=2015-02-21 }}http://www.space.com/scienceastronomy/streaks_mars_streaks_030328.html{{dead link|date=December 2016 |bot=InternetArchiveBot |fix-attempted=yes }} The streaks appear in areas covered with dust. Much of the Martian surface is covered with dust because at more or less regular intervals dust settles out of the atmosphere covering everything. We know a lot about this dust because the solar panels of Mars rovers get covered with dust. The power of the Rovers has been saved many times by the wind, in the form of dust devils that have cleared the panels and boosted the power. So we know that dust falls from the atmosphere frequently.{{Cite web|url=https://www.sciencedaily.com/releases/2009/02/090217101110.htm|title = Mars Spirit Rover Gets Energy Boost from Cleaner Solar Panels}}

It is most generally accepted that the streaks represent avalanches of dust. Streaks appear in areas covered with dust. When a thin layer of dust is removed, the underlying surface appears dark. Much of the Martian surface is covered with dust. Dust storms are frequent, especially when the spring season begins in the southern hemisphere. At that time, Mars is 40% closer to the Sun. The orbit of Mars is much more elliptical than the Earth's. That is, the difference between the farthest point from the Sun and the closest point to the Sun is very great for Mars, but only slight for the Earth. Also, every few years, the entire planet is engulfed in a global dust storm. When NASA's Mariner 9 craft arrived there, nothing could be seen through the dust storm.{{Cite book|isbn = 0-517-00192-6|title = Atlas of the Solar System|last1 = Moore|first1 = Patrick|date = 2 June 1990}}{{cite book|author=Hugh H. Kieffer|title=Mars|url=https://books.google.com/books?id=NoDvAAAAMAAJ|access-date=7 March 2011|year=1992|publisher=University of Arizona Press|isbn=978-0-8165-1257-7}} Other global dust storms have also been observed, since that time.

ESP 036956 1895layers.jpg|Layers in Gordii Dorsum Region, as seen by HiRISE under HiWish program. Dark lines are Dark Slope Streaks.

Esp 036851 1995mesastreaks.jpg|Dark slope streaks on mesa, as seen by HiRISE under HiWish program Location is Amazonis quadrangle.

44802streaks.jpg|Dark slope streaks on mound in Lycus Sulci, as seen by HiRISE under HiWish program

Brain terrain is common in many places on Mars. It is formed when ice sublimates along cracks. The ridges of brain terrain may contain a core of ice. Shadow measurements from HiRISE indicate the ridges are 4–5 meters high.Levy, J., J. Head, D. Marchant. 2009. Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes. Icarus 202, 462–476.

File:ESP 054996 2155brains.jpg|Wide view of brain terrain, as seen by HiRISE under HiWish program

File:54996 2155brains2.jpg|Close view of brain terrain, as seen by HiRISE under HiWish program

File:54996 2155brains.jpg|Close, color view of brain terrain, as seen by HiRISE under HiWish program

Wikimolaamazonisarcadia.jpg|MOLA map showing boundaries for Amazonis Planitia and other regions Colors indicate elevations.

Image:MarsDustDevi-AmazonisPlanitia-MGS-MOC-20010401-E03-00938.gif|Martian Dust Devil - in Amazonis Planitia (April 10, 2001) ([http://www.nasa.gov/mission_pages/MRO/multimedia/pia15116.html also]) ([https://www.youtube.com/watch?v=0t0LWFHB8Qo video (02:19)]).

Image:ESP_024997ridges.jpg|Possible inverted stream channels in Phlegra Dorsa region, as seen by HiRISE under HiWish program. The ridges were probably once stream valleys that have become full of sediment and cemented. So, they became hardened against erosion which removed surrounding material.

Image:26552surfaces.jpg|Surfaces in Amazonis quadrangle, as seen by HiRISE under HiWish program.

44802buttes.jpg|Layered features in Lycus Sulci, as seen by HiRISE under HiWish program

ESP 045198 1900craterlayers.jpg|Wide view of scarp showing layers, as seen by HiRISE under HiWish program

45198 1900craterlayersclose.jpg|Close view of layers from previous image, as seen by HiRISE under HiWish program

ESP 045435 2055troughlayers.jpg|Layers in trough and dark slope streaks, as seen by HiRISE under HiWish program

ESP 045462 1920pedestal.jpg|Pedestal crater with layers, as seen by HiRISE under HiWish program

• Amazonian (Mars)
• Dark slope streaks
• Geography of Mars
• List of plains on Mars
• Medusae Fossae Formation

{{Reflist|colwidth=30em}}

{{Commons category|Amazonis Planitia}}

• [http://www.google.com/mars/#lat=20.468189&lon=-128.671875&q=Amazonis%20Planitia Google Mars zoomable map centered on Amazonis Planitia]
• [https://web.archive.org/web/20070206134933/http://hiroc.lpl.arizona.edu/images/PSP/PSP_001578_2000/ HiRISE image of faulting in Amazonis Planitia]

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Category:Plains on Mars

Category:Amazonis quadrangle

Category:Memnonia quadrangle