Климат, лед, вода, ландшафты

Climate, ice, water, landscapes

Рудой Алексей Николаевич
История Земли. планет, Вселенной....

__История Земли. планет, Вселенной....



Diverted landslides in Valles Marineris

Статья в работе

Diverted landslides in Valles Marineris Post contributed by Dr Peter Grindrod, Department of Earth and Planetary Sciences, University of London Layered deposits on Mars are a globally-pervasive record of the sedimentary history of the planet. These deposits not only preserve long sequences of Mars’ stratigraphic record, but also exhibit evidence for hydrous minerals and aqueous activity, and thus help to define the habitability through time. Layered deposits are therefore high priority exploration targets for current and future missions, including the Mars Science Laboratory Curiosity Rover, which currently sits at the base of an interior layered deposit (ILD) in Gale Crater. Print Image 1. A typical landslide in Valles Marineris, Mars. CTX DTM made at the UK NASA RPIF (Regional Planetary Image Facility) at University College London. Images B21_017688_1685_XN_11S067W and B22_018321_1685_XN_11S068W. Image credit: NASA/JPL/Malin Space Science Systems. Despite their importance, no consensus exists regarding how ILDs form, evolve, and whether they represent a complete sedimentary record. It is currently uncertain whether the modern shape and form of these mounded landforms is representative of their total depositional volume or whether the mounds are degraded examples of once larger deposits. Resolving this controversy has broad implications for not only the sedimentary history of Mars, in terms of how much sediment was deposited globally, but also the planet’s aqueous history and sulfur budget. An unlikely solution to part of this problem can be found by looking at landslide deposits. Landslides on Mars typically have runout distances much larger than equivalent features on Earth, which means that there is a greater chance of them interacting with other features. Typical landslides in the Valles Marineris canyon system on Mars have topographic profiles consisting of a steep headwall in the source region, with the landslide flowing, sometimes large distances, downslope before gradually toeing out onto the surrounding terrain. However, at least three large sets of landslides in Ophir Chasma appear to have noticeably different morphologies to other landslides on Mars. These features differ by having an increase in height towards their front edges, showing distinctive concave scarp faces that are up to 500 m above the base level, and up to 400 m higher than the preceding part of the landslide deposit. These scarps are 1 – 2 km from, and importantly, mimic the shape of the current extent of the ILD outer boundaries. Print Image 2. Example of an obstructed landslide in Ophir Chasma, Mars. CTX DTM made at the UK NASA RPIF (Regional Planetary Image Facility) at University College London. Images B01_009895_1764_XN_03S071W and P22_009750_1765_XN_03S071W. Image credit: NASA/JPL/Malin Space Science Systems. The most likely explanation for the formation of these frontal scarps is that the leading edge of a landslide has piled up in front of an obstacle that has since been removed. The plausibility of such landslide obstruction is demonstrated elsewhere in Coprates Chasma, where landslides have ridden up between 500 and 800 m in height against bedrock material in the centre of Coprates Chasma that has not been subsequently removed. Given that the landslide scarps mimic the outline of the ILDs, it is most likely that the landslide obstacles were ILDs that were larger in the past and have since reduced in size, effectively pulling away from the landslide front edges. Since the landslide event, the ILD mounds have retreated from the landslides by up to 2 km, indicating high erosion rates at the mound front and significant volume loss. As the landslide deposits have likely undergone less erosion than the ILDs, crater counting studies of their surfaces can offer a timestamp on the landslide formation and thus quantify the retreat rate of the ILDs. Print Image 3. Close-up example of an obstructed landslide in Ophir Chasma, Mars. HiRISE DTM made at the UK NASA RPIF (Regional Planetary Image Facility) at University College London. Images PSP_009328_1755 and PSP_010172_1755. Image credit: NASA/JPL/University of Arizona. These crater dating studies show that these ILDs have been in a state of net degradation for at least the last 200-400 Ma of Mars’ history, when the landslides formed. The required erosion rates are higher than previous estimates for this era of Mars’ geological history, but are possible by aeolian abrasion if the mound contains friable materials, or if sublimation of ice within the mound enhances modification. Similar high erosion rates have been found in desert regions on Earth, such as the Qaidam basin, where friable deposits are essentially sandblasted by wind action. In either case, the apparently unique landslide interactions in Valles Marineris indicate that the current form of ILDs of similar morphology on Mars, such as Aeolis Mons in Gale Crater, might under-represent their total depositional volume and likely the global sedimentary record. Further Reading Golombek, M.P., Grant, J.A., Crumpler, L.S., Greeley, R., Arvidson, R.E., Bell, J.F., Weitz, C.M., Sullivan, R., Christensen, P.R., Soderblom, L.A., and Squyres, S.W. (2006), Erosion rates at the Mars Exploration Rover landing sites and long-term climate change on Mars, J. Geophys. Res., 111, E12S10, doi:10.1029/2006JE002754. Grindrod, P.M., and N.H. Warner (2014), Erosion rate and previous extent of interior layered deposits on Mars revealed by obstructed landslides, Geology, 42, 795-798, doi:10.1130/G35790.1. Kite, E.S., Lewis, K.W., Lamb, M.P., Newman, C.E., and Richardson, M.I. (2013), Growth and form of the mound in Gale Crater, Mars: Slope wind enhanced erosion and transport, Geology, 41, 543–546, doi:10.1130/G33909.1. Michalski, J., and Niles, P.B. (2012), Atmospheric origin of Martian interior layered deposits: Links to climate change and the global sulfur cycle, Geology, 40, 419–422, doi:10.1130/G32971.1.

04.12.2014 10:04 10 0 Комментарии
 

Семь марсоходов на Марсе: цели и результаты

Семеро на Марсе: кто и зачем изучает красную планету

Марьяна Пискарева, Тимур Фехретдинов

Марсианский пейзаж. Фото: nasa.gov

Количество космических аппаратов, изучающих Марс как с поверхности, так и с орбиты, достигло семи. 24 сентября на орбиту красной планеты вышел индийский "Мангальян", он же Mars Orbiter Mission. M24.ru рассказывает о том, чем они там занимаются.
 

Slope Streaks on Mars

Planetary Geomorphology Image of the Month

Dr. Mary Bourke, Trinity College Dublin (Tweet @megafloods)

Slope Streaks on Mars

Post by Dr Norbert Schörghofer, University of Hawaii, Honolulu.

Slope streaks are a form of down-slope mass movement on the surface of Mars that frequently occurs on Mars today (Image 1 and 2). Slope streaks were first identified on high-resolution Viking Orbiter images, but their present-day activity was only discovered in Mars Orbiter Camera (MOC) images.

Image 1. A portion of a Mars Orbiter Camera image taken on 1999-10-28.

Image 1. A portion of a Mars Orbiter Camera image taken on 1999-10-28.

Image 2: An Image of the same area taken on 2002-06-10. A large new slope streak formed, while numerous other streaks persisted. North is up and illumination is from the lower left (Schorghofer et al. 2007).

Image 2: An Image of the same area taken on 2002-06-10. A large new slope streak formed, while numerous other streaks persisted. North is up and illumination is from the lower left (Schorghofer et al. 2007).

04.03.2014 15:22 312 0 Комментарии
 

Paleolakes on Mars

Paleolakes on Mars

Post by Dr. Gino Erkeling, Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Germany

The hypothesis of ancient Martian standing bodies of water, which might have occupied the lowlands of the northern hemisphere and which might have existed in local- to regional-scale paleolakes once in Martian history, is one of the most important subjects of ongoing discussion in Mars research (e.g., Parker et al., 1989, 1993; Head et al., 1999; Cabrol and Grin, 1999, 2001; Clifford and Parker, 2001; Kreslavsky and Head, 2002; Carr and Head, 2003; Ghatan and Zimbelman, 2006; Di Achille and Hynek, 2010; Mouginot et al., 2012). The case for large standing bodies of liquid water, including lakes, seas and oceans, is attributed to a complex hydrologic cycle that may have once existed on Mars in the Noachian (>3.7 Ga) and perhaps also in the Hesperian (>3.1 Ga).

Erkeling_etal_2012_IAG_figure

The existence of oceans, seas or lakes is supported by a large variety of morphologic landforms, including ridges, wave-cut platforms and coastal cliffs (e.g., Parker et al., 1993; Head et al., 1999; Webb, 2004; Ghatan and Zimbelman, 2006; Erkeling et al, 2012) and associated delta deposits (e.g., Hauber et al., 2009; Di Achille and Hynek, 2010). Some of these morphologies appear along two global “paleoshorelines” that represent the two most continuous contacts on Mars and possibly reflect different water levels, i.e., the Arabia “shoreline” and the Deuteronilus “shoreline” (e.g., Parker et al., 1989, 1993; Head et al., 1999; Clifford and Parker, 2001; Carr and Head, 2003; Ghatan and Zimbelman, 2006).

A series of morphologic landforms indicative of fluvial and lacustrine environments in the Libya Montes and seas in Isidis Planitia have been identified at three different elevation levels along the boundary between southern Isidis Planitia and the Libya Montes highlands (Image 1 a). In particular, (1) local occurrences of valleys and associated alluvial fans, a delta and an open-basin paleolake between -2500 and -2800 meters (Image 1b), (2) a series of possible coastal cliffs of the Arabia shoreline at -3600 and -3700 meters (Image 1c), and (3) the Deuteronilus shoreline contact as an onlap morphology, i.e. the Isidis interior plains are superposed onto the Isidis exterior plains (Image 1d).

The geologic setting and chronostratigraphic sequence, that indicate Late Noachian landforms at the Libya / Isidis contact, Hesperian landforms at the Arabia shoreline and Early Amazonian landforms at the Deuteronilus contact, are consistent with the proposed Hesperian climate change from warm and wet to cold and dry conditions.

05.02.2014 08:30 266 0 Комментарии
 

Как солнечный цикл влияет на Землю, и чего ждать от Солнца в ближайшие годы и десятилетия

Пульс Солнца падает: впадает ли оно в спячку?

 

Астрофизик Сергей Богачев из Физического института имени Лебедева РАН рассказывает, как был обнаружен солнечный цикл, как он влияет на Землю, и чего ждать от Солнца в ближайшие годы и десятилетия.

С жизнью Солнца связано множество страхов и ожиданий — люди боятся магнитных бурь, климатических катаклизмов, которые могут вызвать изменения солнечного цикла. Астрофизик Сергей Богачев из Физического института имени Лебедева РАН рассказывает, как был обнаружен солнечный цикл, как он влияет на Землю, и чего ждать от Солнца в ближайшие годы и десятилетия.

10.11.2013 19:46 408 0 Комментарии
 
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