Late Amazonian Ice Survival in Kasei Valles, Mars
Late Amazonian Ice Survival in Kasei Valles, Mars
复制标题
火星卡西山谷的亚马逊晚期冰生存
DOI：
--
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
B. Hubbard
中科院分区：
文献类型：
--
作者：
A. Hepburn;F. Ng;T. Holt;B. Hubbard
火星上的高倾角漂移被假设为重新分配了两极的水，以滋养中纬度冰川。今天位于那里的不同类型的粘性流动特征(埋藏在沉积地幔下的富冰沉积物)提供了这一过程的证据，包括叶状碎屑停机坪(LDAs)。在高倾角的极端情况下，冰可能会持续存在到更靠近赤道的地方，正如许多神秘的凹陷所表明的那样，这些凹陷的一侧被孤立的台地或悬崖包围，另一侧被熔岩单元包围。这些凹陷划分了流淌的熔岩和幽灵LDAs(GLDAs)之间过去的相互作用，后者早已消失。我们称这些特征为GLDA凹陷，除了它们的空间范围外，人们对这些特征知之甚少。这些低地表明热带冰川在∼100,000平方公里范围内消失。为了限制它们在喀西谷的历史，我们根据陨石坑的数量得出了GLDA凹陷、台地和熔岩流的模型年龄。我们使用受GLDA凹陷地形约束的冰川冰的2D模型来近似以前冰川沉积的表面和体积。该模型沿着垂直于GLDA凹陷边界的多条流线重建了以前的冰面。这一重建表明，当熔岩侵位时，在∼1.3Ga处存在1,400-3,500千米--类似于地球上冰岛目前的冰。测年结果显示，在熔岩侵位后，GLDA存活了长达10亿年，直到最终消亡。
High‐obliquity excursions on Mars are hypothesized to have redistributed water from the poles to nourish mid‐latitude glaciers. Evidence of this process is provided by different types of viscous flow features (ice‐rich deposits buried beneath sediment mantle) located there today, including lobate debris aprons (LDAs). During high‐obliquity extremes, ice may have persisted even nearer the equator, as indicated by numerous enigmatic depressions bounded on one side by either isolated mesas or scarps, and on the other by a lava unit. These depressions demarcate the past interaction between flowing lava and ghost LDAs (GLDAs), which have long since disappeared. We term these features GLDA depressions, about which little is known besides their spatial extent. This collection of depressions implies tropical ice loss over an area ∼100,000 km2. To constrain their history in Kasei Valles, we derive model ages for GLDA depressions, mesas, and the lava flow from crater counts. We use a 2D model of glacial ice constrained by the topography of GLDA depressions to approximate the surface and volume of former glacial ice deposits. The model reconstructs former ice surfaces along multiple flow lines orientated normal to GLDA depression boundaries. This reconstruction indicates that 1,400–3,500 km3 of ice—similar to that present in Iceland on Earth—existed at ∼1.3 Ga when the lava was emplaced. Dating shows that the GLDAs survived for up to ∼1 billion years following lava emplacement, before its final demise.
影响因子：
3.4
作者：
Clark C
通讯作者：
Clark C