緯度相關覆蓋層

大部分火星表面都披覆了一層厚厚的富冰覆蓋層,該覆蓋層是過去多次從天空飄落的冰核塵埃所組成[1] [2] [3]。在部分地區可看到覆蓋層中的一些分層[4]

從天空降落的冰核塵埃,很好地證明了這層覆蓋層富含水冰。許多表面常見的多邊形形狀也表明土壤中富含冰。2001火星奧德賽號發現了高含量的(可能來自水)[5][6] [7] [8] [9]。從軌道上進行的熱輻射測量表明了冰的存在[10] [11]鳳凰號火星探測器降落在一片多邊形區域中,它發現了水冰,並進行了直接觀測[12][13],事實上,它的着陸火箭暴露了純冰。理論預測在幾厘米厚的土壤下會發現冰。該覆蓋層被稱為「緯度相關覆蓋層」,因為它的出現與緯度有關。正是這層覆蓋層後來的破裂,才形成了多邊形地面。這種富含水冰地面的破裂是根據物理作用所預測的[14][15] [16] [17][18] [19][20]。另一種表面被稱為「腦紋地形」,因為它看起來像人腦的表面。當兩種區域同時出現時,腦紋地形高度較多邊形地面更低。

儘管相鄰下層的腦紋地形參差不齊,但從頂層開始,多邊形層相當平整。據信,含多邊形的覆蓋層深度需達10-20米,才能形成平整表面。在所有的冰消失之前,覆蓋層會持續很長一段時間,因為頂部會形成一層保護性的滯留沉積物[21] [22] [23]。覆蓋層中含有冰和塵埃。當一定數量的冰升華後,塵埃停留在頂部,形成滯留沉積層[24] [25] [26] [27]。 根據多邊形地面的總面積計算,估計覆蓋層中鎖住的總水量約有10米深,這一體積相當於在整個星球覆蓋了一層2.5米深的水。但相比之下,地球北極南極冰蓋融化的水則可覆蓋整個星球30米深[28]

覆蓋層形成於火星氣候與現在不同的時期[29] [30] [31],火星自轉軸的傾斜或傾角變化很大[32] [33] [34],而地球的傾斜變化則很小,因為我們相當大的月球穩定了地球。火星只有兩顆非常小衛星,它們沒有足夠的引力來穩定火星的傾斜。當火星傾斜度超過40度(今天是25度)左右時,冰就會沉積在某些緯度帶上,而這些緯度帶現今存在着大量的覆蓋層 [35] [36]。  

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參考文獻 

  1. ^ Hecht, M. 2002. Metastability of water on Mars. Icarus 156, 373–386
  2. ^ Mustard, J., et al. 2001. Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice. Nature 412 (6845), 411–414.
  3. ^ Pollack, J., D. Colburn, F. Flaser, R. Kahn, C. Carson, and D. Pidek. 1979. Properties and effects of dust suspended in the martian atmosphere. J. Geophys. Res. 84, 2929-2945.
  4. ^ 存档副本. [2021-08-11]. (原始內容存檔於2017-09-02). 
  5. ^ Boynton, W., and 24 colleagues. 2002. Distribution of hydrogen in the nearsurface of Mars: Evidence for sub-surface ice deposits. Science 297, 81–85
  6. ^ Kuzmin, R, et al. 2004. Regions of potential existence of free water (ice) in the near-surface martian ground: Results from the Mars Odyssey High-Energy Neutron Detector (HEND). Solar System Research 38 (1), 1–11.
  7. ^ Mitrofanov, I. et al. 2007a. Burial depth of water ice in Mars permafrost subsurface. In: LPSC 38, Abstract #3108. Houston, TX.
  8. ^ Mitrofanov, I., and 11 colleagues. 2007b. Water ice permafrost on Mars: Layering structure and subsurface distribution according to HEND/Odyssey and MOLA/ MGS data. Geophys. Res. Lett. 34 (18). doi:10.1029/2007GL030030.
  9. ^ Mangold, N., et al. 2004. Spatial relationships between patterned ground and ground ice detected by the neutron spectrometer on Mars. J. Geophys. Res. 109 (E8). doi:10.1029/ 2004JE002235.
  10. ^ Feldman, W., and 12 colleagues. 2002. Global distribution of neutrons from Mars:Results from Mars Odyssey. Science 297, 75–78.
  11. ^ Feldman, W., et al. 2008.North to south asymmetries in the water-equivalent hydrogen distribution at high latitudes on Mars. J. Geophys. Res. 113. doi:10.1029/2007JE003020.
  12. ^ Bright Chunks at Phoenix Lander's Mars Site Must Have Been Ice頁面存檔備份,存於互聯網檔案館) – Official NASA press release (19.06.2008)
  13. ^ Confirmation of Water on Mars. Nasa.gov. 2008-06-20 [2012-07-13]. (原始內容存檔於2008-07-01). 
  14. ^ Mutch, T.A., and 24 colleagues, 1976. The surface of Mars: The view from the Viking2 lander. Science 194 (4271), 1277–1283.
  15. ^ Mutch, T., et al. 1977. The geology of the Viking Lander 2 site. J. Geophys. Res. 82, 4452–4467.
  16. ^ Levy, J., et al. 2009. Thermal contraction crack polygons on Mars: Classification, distribution, and climate implications from HiRISE observations. J. Geophys. Res. 114. doi:10.1029/2008JE003273.
  17. ^ Washburn, A. 1973. Periglacial Processes and Environments. St. Martin’s Press,New York, pp. 1–2, 100–147.
  18. ^ Mellon, M. 1997. Small-scale polygonal features on Mars: Seasonal thermal contractioncracks in permafrost. J. Geophys. Res. 102, 25,617-625,628.
  19. ^ Mangold, N. 2005. High latitude patterned grounds on Mars: Classification, distribution and climatic control. Icarus 174, 336–359.
  20. ^ Marchant, D., J. Head. 2007. Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climate change on Mars. Icarus 192, 187–222
  21. ^ Marchant, D., et al. 2002. Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon valley, southern Victoria land, Antarctica. Geol. Soc. Am. Bull. 114, 718–730.
  22. ^ Mellon, M., B. Jakosky. 1995. The distribution and behavior of Martian ground ice during past and present epochs. J. Geophys. Res. 100, 11781–11799.
  23. ^ Schorghofer, N., 2007. Dynamics of ice ages on Mars. Nature 449, 192–194.
  24. ^ Madeleine, J., F. Forget, J. Head, B. Levrard, F. Montmessin. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.
  25. ^ Schorghofer, N., O. Aharonson. 2005. Stability and exchange of subsurface ice on Mars. J. Geophys. Res. 110 (E05). doi:10.1029/2004JE002350.
  26. ^ Schorghofer, N., 2007. Dynamics of ice ages on Mars. Nature 449 (7159), 192–194
  27. ^ Head, J., J. Mustard, M. Kreslavsky, R. Milliken, D. Marchant. 2003. Recent ice ages on Mars. Nature 426 (6968), 797–802.
  28. ^ Levy, J. et al.  2010.  Thermal contraction crack polygons on Mars:  A synthesis from HiRISE, Phoenix, and terrestrial analog studies.  Icarus: 206, 229-252.
  29. ^ Mustard, J., et al.  2001. Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice. Nature 412 (6845), 411–414.
  30. ^ Kreslavsky, M.A., Head, J.W., 2002. High-latitude Recent Surface Mantle on Mars: New Results from MOLA and MOC. European Geophysical Society XXVII, Nice.
  31. ^ Head, J.W., Mustard, J.F., Kreslavsky, M.A., Milliken, R.E., Marchant, D.R., 2003.Recent ice ages on Mars. Nature 426 (6968), 797–802.
  32. ^ name= Touma J. and J. Wisdom.  1993.  The Chaotic Obliquity of Mars.  Science 259, 1294-1297.
  33. ^  Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel.   2004.   Long term evolution and chaotic diffusion of the insolation quantities of Mars.  Icarus 170, 343-364.  
  34. ^ Levy, J., J. Head, D. Marchant, D. Kowalewski.  2008.  Identification of sublimation-type thermal contraction crack polygons at the proposed NASA Phoenix landing site: Implications for substrate properties and climate-driven morphological evolution. Geophys. Res. Lett. 35. doi:10.1029/2007GL032813.
  35. ^ Kreslavsky, M., J. Head, J.  2002.  Mars: Nature and evolution of young, latitude-dependent water-ice-rich mantle. Geophys. Res. Lett. 29, doi:10.1029/ 2002GL015392.
  36. ^ Kreslavsky, M., J. Head.  2006.  Modification of impact craters in the northern plains of Mars: Implications for the Amazonian climate history. Meteorit. Planet. Sci. 41, 1633–1646.