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Holden is a 140 km wide crater situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars, located with the southern highlands. It is named after Edward Singleton Holden, an American astronomer, and the founder of the Astronomical Society of the Pacific.〔http://www.google.com/mars/〕 It is part of the * Uzboi-Landon-Morava (ULM) system. Like Gusev, it is notable for an outlet channel, Uzboi Vallis, that runs into it, and for many features that seem to have been created by flowing water. It's believed that Holden Crater was formed by an impact between the Noachian to Hesperian Epochs.〔Grant, J. et al. 2008. HiRISE imaging of impact megabreccia and sub-meter aqueous strata in Holden Crater, Mars. Geology: 36, 195-198.〕 〔Pondrelli, M. et al. 2005. Complex evolution of paleoslacustrine systems on Mars: An example from the Holden crater. J. Geophys. Res. 110, E04016, doi:10.1029/2004JE002335.〕 〔Scott, D., K. Tanaka. 1986. Geologic map of the western equatorial region of Mars, U. S. Geol. Surv. Misc. Invest. Ser. Map I-1802-A.〕 The crater's rim is cut with gullies, and at the end of some gullies are fan-shaped deposits of material transported by water.〔Moore, J. A. Howard. 2005. Large alluvial fans on Mars. Journal of Geophysical Research: 110, E04005.〕 The crater is of great interest to scientists because it has some of the best-exposed lake deposits. One of the layers has been found by the Mars Reconnaissance Orbiter to contain clays.〔Murchie, S. et al. 2009. A synthesis of Martian aqueous mineralogy after 1 Mars year of observations from the Mars Reconnaissance Orbiter. Journal of Geophysical Research: 114.〕〔Grotzinger, J. and R. Milliken (eds.) 2012. Sedimentary Geology of Mars. SEPM〕 Clays only form in the presence of water. There are two unit of sediments in the crater. The lower unit formed in a large lake. It is believed the lake waters originated from the crater walls/or groundwater. Water from the crater walls may have come from precipitation when the Martian climate was different. The upper unit formed when water that was ponded to the south in Uzboi Vallis broke through Holden's rim.〔Grant, J. et al. 2008. HiRISE imaging of impact megabreccia and sub-meter aqueous strata in Holden Crater, Mars. Geology: 36, 195-198.〕 It is believed that great amount of water went through the rim; one flow was caused by a body of water larger than Earth's Lake Huron.〔http://hirise.lpl.arizona.edu/PSP_003077_1530〕 Some of the evidence for such a large flow of water is the presence of boulders tens of meters in size sticking above the surface. To transport such huge rocks takes a great deal of water. Holden is an old crater, containing numerous smaller craters, many of which are filled with sediment. The crater's central mountain is also obscured by sediment. Holden Crater was a proposed landing site for NASA's Mars Science Laboratory, until Gale Crater was deemed a better landing site. Just to the north east of Holden Crater is Eberswalde Crater which contains a large delta. The lower beds of Holden are thought by some to maybe similar to materials in Eberswalde Crater.〔Malin, M., K. Edgett. 2003. Evidence for persistent flow and aqueous sedimentation on Mars. Science: 302, 1931-1934.〕 〔Moore, J. et al. 2003. Marian layered fluvial deposits: implications for Noachian climate scenarios. Geophys. Res. letts. 30, doi:10,1029/2003GL019002.〕 However, Holden Crater is now considered a potential landing site for the ''Mars 2020'' rover. Image:Holden Crater Rim.jpg|West Rim of Holden Crater, as seen by THEMIS. Click on image to see more details. Image is located in the Margaritifer Sinus quadrangle. Image:Holden Crater Close-up.JPG|Close-up of Channels on Rim of Holden Crater, as seen by THEMIS. Click on image to see more details. ==Geologic history of Holden Crater== Studies of the whole region around Holden Crater have resulted in an understanding of a complex sequence of events that shaped the crater, which included two different lakes.〔Grant, J. 1987. The geomorphic evolution of Eastern Margaritifer Sinus, Mars. Adv. Planet. Geol. NASA Tech memo. 89889871, 1-268.〕 A large series of rivers called the Uzboi-Ladon-Morava (ULM) system drained water from the Argyre Basin, site of a large lake.〔Baker, V. 1982. The Channels of Mars. University of Texas Press, Austin, TX.〕〔Philillips, R. et al. 2001. Ancient geodynamics and global-scale hydrology on Mars. Science: 291, 2587_2591.〕〔Saunders, S. 1979. Geologic map of the Margaritifer Sinus quadrangle of Mars, U.S> Geol. Surv. Misc. Invest. Ser. Map I-1144, scale 1:5M.〕 When an impact occurred and produced Holden Crater, the system was blocked by a crater rim almost a kilometer in height. Eventually water from drainage from the walls, with possibly a contribution from groundwater, collected to make the first lake.〔Cabrol, N. and E. Grin (eds.). 2010. Lakes on Mars. Elsevier. NY〕 〔Malin, M., K. Edgett. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science: 302, 1931–1934.〕〔Moore, J., A. Howard. 2005. Large alluvial fans on Mars. J. Geophys. Res. 110, E04005, doi:10.1029/2005JE002352.〕 This lake was deep and long lasting. The lowest level of sedimentary rocks was deposited in this lake. Much water was inbounded in Uzboi Vallis because the rim of Holden Crater blocked the flow. Some of the backed up water came from Nirgal Vallis which had a discharge of 4800 cubic meters/second.〔Irwin, J., R. Craddock, R. Howard. 2005. Interior channels in Martian valley networks: Discharge and runoff production. Geology: 33,489-492.〕 At a certain point the stored water broke through the rim of Holden and created a second, shorter lived lake 200–250 m deep.〔Grant, J., R. Irwin, S. Wilson. 2010. Aqueous depositional settings in Holden crater, Mars In Cabrol, N. and E. Grin (eds.). 2010. Lakes on Mars. Elsevier. NY.〕 Water with a depth of at least 50 m entered Holden at a rate that 5-10 times the discharge of the Mississippi River.〔Grant, J., T. Parker. 2002. Drainage evolution of the Margaritifer Sinus region, Mars. J. Geophysic. Res. 107, doi:10.1029/2001JE001678.〕〔Komar, P. 1979. Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on Earth. Icarus: 37, 156-181.〕〔Grant, J. et al. 2008. HiRISE imaging of impact megabreccia and sub-meter aqueous strata in Holden Crater, Mars. Geology: 36, 195-198.〕〔Irwin, et al. 2005. An intense terminal epoch of widespread fluvial activity on early Mars: 2. Increased runoff and paleolake development. J. Geophysical. Res. 110, E12S14, doi: 10.1029/2005JE002460.〕 Terraces and the presence of large rocks (tens of meters across) support these high discharge rates.〔Cabrol, N. and E. Grin (eds.). 2010. Lakes on Mars. Elsevier. NY〕 〔〔Boothroyd, J. 1983. Fluvial drainage systems in the Ladon Basin area: Margaritifer Sinus area, Mars. Geol. Soc. Am. Abstr. Programs 15, 530〕〔Grant, J. 1987. The geomorphic evolution of Eastern Margaritifer Sinus, Mars. Adv. Planet. Geol. NASA Tech memo. 89871, 1-268.〕〔Parker, T. 1985. Geomorphology and geology of the southwestern Margaritifer Sinus-northern Argyre region of Mars, California State University, M. S. Thesis, Los Angeles, California〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Holden (Martian crater)」の詳細全文を読む スポンサード リンク
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