腦紋地形

腦紋地形(Brain terrain)也被稱為腦珊瑚結(Knobs-brain coral)和腦珊瑚地形(brain coral terrain),是在火星舌狀岩屑坡線狀谷底沉積同心坑沉積表面發現的,由複雜的壟脊所組成的一種地貌特徵。由於外觀酷似人腦表面的腦紋,所以被命名為腦紋地形,其中寬脊被稱為「細胞閉合型」腦紋地形,而不太常見的窄脊則被稱為「細胞開放型」腦紋地形[1]

據認為,寬脊的細胞閉合型地形中包裹着冰核,一旦冰核融化消失時,寬脊中心就會塌陷,形成開放細胞型的窄脊。來自高分辨率成像科學設備的陰影測量顯示,這些壟脊有4-5米高[1]。腦紋地形被觀察到由所謂的「平原上部單元」構成,這一過程起始於應力產生的裂紋,而平原上部單元則是累積的降雪和冰核塵埃覆蓋層[2]

如今,人們普遍認可如舌狀岩屑坡線狀谷底沉積同心坑沉積等類冰川結構都是相互關聯的,因為它們具有相同的表面結構。峽谷中冰川類結構和冰斗狀的凹壁可能會與其他類型的因素結合,形成舌狀岩屑坡。當相向的舌狀岩屑坡匯聚時,就會產生出線狀谷底沉積[3],它們可能都富含水冰物質。 在北半球火星分界線附近區域發現了很多此類特徵,大部分位於東經0度至70度之間[4],該區域附近的地區被用一些古地名命名:都特羅尼勒斯桌山群普羅敦尼勒斯桌山群尼羅瑟提斯桌山群。舌狀岩屑坡、線狀谷底沉積和同心坑沉積中可能有大量被塵土和岩屑覆蓋的積冰[5][6][7][8]

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參考文獻

  1. ^ 1.0 1.1 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.
  2. ^ Baker, D., J. Head. 2015. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implication for the record of mid-latitude glaciation. Icarus: 260, 269-288.
  3. ^ Souness, C. and B. Hubbard.  2013. An alternative interpretation of late Amazonian ice flow: Protonilus Mensae, Mars. Icarus 225, 495-505.
  4. ^ Barlow, N. 2008. Mars: An Introduction to its Interior, Surface and Atmosphere. Cambridge University Press. ISBN 978-0-521-85226-5
  5. ^ Head, J. and D. Marchant. 2006. Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars: Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band. Lunar. Planet. Sci. 37. Abstract 1127
  6. ^ Head, J. and D. Marchant. 2006. Modifications of the walls of a Noachian crater in Northern Arabia Terra (24 E, 39 N) during northern mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of Lobate Debris Aprons and their relationships to lineated valley fill and glacial systems. Lunar. Planet. Sci. 37. Abstract 1128
  7. ^ Head, J., et al. 2006. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for the late Amazonian obliquity-driven climate change. Earth Planet. Sci. Lett. 241. 663-671
  8. ^ Head, J., et al. 2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation. Geophys. Res Lett. 33