{{Short description|Map of a region on Mars}} {{Infobox feature on celestial object | name = Sinus Sabaeus quadrangle | image = [[File:USGS-Mars-MC-20-SinusSabaeusRegion-mola.png|300px]] | caption = Map of the Sinus Sabaeus quadrangle based on data from the [[Mars Orbiter Laser Altimeter]] (MOLA). The highest elevations are shown in red, and the lowest in blue. | coordinates = {{coord|15|S|337.5|W|globe:Mars_type:landmark|display=inline,title}} }}
[[File:PIA00180-MC-20-SinusSabeusRegion-19980605.jpg|thumb|300px|Image of the Sinus Sabaeus quadrangle (MC-20). Most of the region consists of heavily cratered highlands. The northern part includes [[Schiaparelli (Martian crater)|Schiaparelli Crater]].]]
The '''Sinus Sabaeus quadrangle''' is one of the [[List of quadrangles on Mars|30 quadrangle maps of Mars]] created by the [[United States Geological Survey]] (USGS) [[Astrogeology Science Center]]. It is designated as MC-20 (Mars Chart–20).<ref>Davies, M.E.; Batson, R.M.; Wu, S.S.C. “Geodesy and Cartography” in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars''. University of Arizona Press: Tucson, 1992.</ref>
The Sinus Sabaeus quadrangle spans the region from 315° to 360° west longitude and 0° to 30° south latitude. It includes the prominent [[Schiaparelli (crater on Mars)|Schiaparelli Crater]], a large, easily recognizable impact feature located near the Martian equator. The quadrangle also encompasses portions of the ancient, heavily cratered terrains of [[Noachis Terra]] and [[Terra Sabaea]].
The name "Sinus Sabaeus" derives from a classical albedo feature named after an incense-producing region south of the Arabian Peninsula, near the Gulf of Aden.<ref>Blunck, J. 1982. ''Mars and its Satellites.'' Exposition Press, Smithtown, N.Y.</ref>
{{Main|Classical albedo features on Mars}} {{Main|Planetary nomenclature#Mars}}
== Layers == [[Wislicenus Crater]] and the Schiaparelli basin crater contain layers, also called strata. Many places on Mars show rocks arranged in layers.<ref name="Grotzinger, J 2012. PM">Grotzinger, J. and R. Milliken (eds.) 2012. ''Sedimentary Geology of Mars.'' SEPM</ref> Sometimes the layers are of different colors. Light-toned rocks on Mars have been associated with hydrated minerals like [[sulfates]]. The [[Mars rover]] ''[[Opportunity (rover)|Opportunity]]'' examined such layers closely with several instruments. Some layers are probably composed of fine particles because they appear to break up into fine dust. Other layers break up into large boulders, suggesting they are much harder. [[Basalt]], a volcanic rock, is thought to be present in the layers that form boulders. Basalt has been identified in many locations on Mars. Instruments on orbiting spacecraft have detected [[clay]] (also known as [[phyllosilicates]]) in some layers. Scientists are excited about finding hydrated minerals, such as sulfates and clays, on Mars because they are usually formed in the presence of water.<ref>{{Cite web|url=http://themis.asu.edu/features/nilosyrtis|title=Target Zone: Nilosyrtis? | Mars Odyssey Mission THEMIS}}</ref> Locations containing clays and/or other hydrated minerals are promising places to search for evidence of life.<ref>{{Cite web|url=http://hirise.lpl.arizona.edu/PSP_004046_2080|title=HiRISE | Craters and Valleys in the Elysium Fossae (PSP_004046_2080)}}</ref>
Rock can form layers in a variety of ways. Volcanoes, wind, and water can produce layers.<ref>{{Cite web|url=https://hirise.lpl.arizona.edu/?PSP_008437_1750|title=HiRISE | High Resolution Imaging Science Experiment|website=hirise.lpl.arizona.edu}}</ref> Layers can be hardened by the action of groundwater. Martian groundwater likely moved hundreds of kilometers, dissolving many minerals from the rock it passed through. When groundwater surfaces in low areas containing sediments, the thin Martian atmosphere causes water to evaporate, leaving behind minerals as deposits and/or cementing agents. Consequently, layers of dust are less likely to erode easily, as they become cemented together. On Earth, mineral-rich waters often evaporate, forming large deposits of salts and other minerals. Sometimes, water flows through Earth's aquifers and then evaporates at the surface, much like what is hypothesized for Mars. One location where this occurs on Earth is the [[Great Artesian Basin]] in [[Australia]].<ref>Habermehl, M. A. (1980) The Great Artesian Basin, Australia. J. Austr. Geol. Geophys. 5, 9–38.</ref> On Earth, the hardness of many [[sedimentary rock]]s, such as [[sandstone]], is largely due to the cement that forms as water passes through.
==Schiaparelli Crater== [[File:ESP 046814 1785schiaparellimola.jpg|thumb|upright=1.2|MOLA map of the area around Schiaparelli Crater]] [[Schiaparelli (Martian crater)|Schiaparelli]] is a large impact crater on [[Mars]], located near the planet's equator. It has a diameter of approximately {{convert|461|km|mi|sp=us}} and is centered at a latitude of 3° south and a longitude of 344° east. Some regions within Schiaparelli display numerous layers that may have formed through aeolian (wind-driven) processes, volcanic activity, or sedimentary deposition in the presence of water.
== Other craters == When a [[comet]] or [[asteroid]] collides at high speed with the surface of [[Mars]], it creates a primary [[impact crater]]. The impact can also eject a large number of rocks, which may fall back to the surface and form [[secondary craters]].<ref>{{Cite web|url=http://hirise.lpl.arizona.edu/science_themes/impact.php|title=HiRISE | Science Themes: Impact Processes}}</ref> These secondary craters often appear in clusters. Because all the craters in such a cluster are subject to the same erosion patterns, they tend to appear similarly weathered, indicating that they are likely of the same age. If the secondary craters originated from a single, large, nearby impact, they would have formed nearly simultaneously.
The image below of [[Denning (Martian crater)|Denning Crater]] shows an example of a cluster of secondary craters.
Impact craters generally have a raised rim and surrounding [[ejecta]] deposits, whereas [[volcanic craters]] typically lack both features. As impact craters increase in size—typically those greater than 10 km in diameter—they often develop a [[central peak]].<ref name="lpi.usra.edu">{{Cite web|url=http://www.lpi.usra.edu/publications/slidesets/stones/|title=Stones, Wind, and Ice: A Guide to Martian Impact Craters}}</ref> This peak results from the rebound of the crater floor immediately after the impact.<ref name="Kieffer1992">{{cite book|author=Hugh H. Kieffer|title=Mars|url=https://books.google.com/books?id=NoDvAAAAMAAJ|access-date=7 March 2011|date=1992|publisher=University of Arizona Press|isbn=978-0-8165-1257-7}}</ref>
By measuring the diameter of a crater, scientists can estimate its original depth using empirical ratios. This relationship has helped researchers determine that many Martian craters are partially filled with material—much of which is believed to be [[ice]] deposited during earlier climatic periods.<ref>Garvin, J., et al. 2002. Global geometric properties of Martian impact craters. Lunar Planet Sci. 33. Abstract #1255.</ref>
Craters also often expose subsurface [[geological formation|geological layers]] that were previously buried. During an impact, material from deep underground is ejected onto the surface, allowing scientists to study what lies beneath the Martian crust.
== White rock in Pollack crater == [[File:Whiterock.JPG|thumb|upright=1.2|Whiterock on the crater floor may be the remnant of a once much larger deposit. The arrow indicates that the deposit likely extended much farther in the past. Image taken by [[THEMIS]].]]
Within this region lies [[Pollack (crater)|Pollack Crater]], which contains light-toned rock deposits. Mars has a significantly older surface compared to Earth. While much of Earth's surface is only a few hundred million years old due to active geological processes, large portions of the Martian surface are more than a billion years old. Some areas on Mars have undergone multiple cycles of deposition, erosion, and burial beneath newer layers.
In the 1970s, the [[Mariner 9]] spacecraft photographed a striking feature within a crater, which was named "White Rock." Initially, it was thought to be a [[salt deposit]] due to its light color. However, more recent data from instruments on the [[Mars Global Surveyor]] suggest that the material is likely [[volcanic ash]] or [[fine dust]] rather than salt.<ref name="Grotzinger, J 2012. PM"/> Later analysis revealed that "White Rock" only appears exceptionally bright because the surrounding terrain is unusually dark—giving the illusion of high contrast.
Today, scientists believe that White Rock represents a remnant of a much larger sedimentary deposit that once filled the entire crater. Over time, much of it was eroded away, leaving only a fragment of the original formation. The image shows a detached outcrop of the same light-toned material some distance from the main deposit, supporting the idea that the white material once covered a significantly larger area.<ref>{{Cite web|url=http://space.com/scienceastronomy/solarsystem/mars_daily_020419.html|title = Mars: What We Know About the Red Planet|website = [[Space.com]]|date = October 2021}}</ref>
==Channels in Sinus Sabaeus quadrangle== There is substantial evidence that water once flowed through river valleys on Mars.<ref>Baker, V. R., et al. 2015. "Fluvial geomorphology on Earth-like planetary surfaces: a review." ''Geomorphology'', 245, 149–182.</ref><ref>Carr, M. H. 1996. ''Water on Mars''. Oxford University Press.</ref> Images of sinuous, branching channels—strongly resembling terrestrial river systems—have been observed since the early 1970s, beginning with data from the [[Mariner 9]] orbiter.<ref>Baker, V. R. 1982. ''The Channels of Mars''. University of Texas Press, Austin.</ref><ref>Baker, V. R., Strom, R. G., Gulick, V. C., Kargel, J. S., Komatsu, G., Kale, V. S. 1991. "Ancient oceans, ice sheets, and the hydrological cycle on Mars." ''Nature'', 352, 589–594.</ref><ref>Carr, M. H. 1979. "Formation of Martian flood features by release of water from confined aquifers." ''Journal of Geophysical Research'', 84, 2995–3007.</ref><ref>Komar, P. D. 1979. "Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on Earth." ''Icarus'', 37, 156–181.</ref>
A study published in June 2017 estimated that the volume of water required to carve the valley networks on Mars exceeded even the volume of the hypothesized ancient Martian ocean. This suggests that water may have been recycled repeatedly—from the ocean to rainfall and back—across a planet-wide hydrological cycle.<ref>{{Cite web|url=http://spaceref.com/mars/how-much-water-was-needed-to-carve-valleys-on-mars.html|title=How Much Water Was Needed to Carve Valleys on Mars? - SpaceRef|date=5 June 2017}}</ref><ref>Luo, W., et al. 2017. "New Martian valley network volume estimate consistent with ancient ocean and warm and wet climate." ''Nature Communications'', 8, Article number: 15766. doi:10.1038/ncomms15766</ref>
{{Main|Valley networks (Mars)}} {{Main|Outflow channels}}
==See also== {{div col}} * [[Climate of Mars]] * [[Dike (geology)]] * [[Geology of Mars]] * [[Groundwater on Mars]] * [[HiRISE]] * [[HiWish program]] * [[Impact crater]] * [[List of quadrangles on Mars]] * [[Martian Craters]] * [[Valley network (Mars)]] * [[Vallis (planetary geology)|Vallis]] * [[Water on Mars]] {{div col end}}
==References== {{reflist|colwidth=30em}}
==Further reading== * Grotzinger, J. and R. Milliken (eds.). 2012. Sedimentary Geology of Mars. SEPM.
== External links == {{commons category|Sinus Sabaeus quadrangle}} {{Mars quadrangle layout}} {{Mars}} {{Portal bar|Solar System}}
{{DEFAULTSORT:Sinus Sabaeus Quadrangle}} [[Category:Sinus Sabaeus quadrangle| ]] [[Category:Mars]]