Paucity of candidate coastal constructional landforms along proposed shorelines on Mars: Implications for a northern lowlands-filling ocean
Paucity of candidate coastal constructional landforms along proposed shorelines on Mars: Implications for a northern lowlands-filling ocean
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火星拟定海岸线沿线缺乏候选沿海建设地貌：对北部低地填充海洋的影响
DOI：
10.1016/j.icarus.2006.06.007
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发表时间：
2006
期刊：
影响因子：
3.2
通讯作者：
J. Zimbelman
中科院分区：
文献类型：
--
作者：
G. J. Ghatan;J. Zimbelman
火星北方低地曾被海洋占据的说法，很大程度上是间接地基于外流通道流入低地，而直接基于低地边缘沿着的侵蚀特征，这些侵蚀特征被解释为波浪作用的结果。两个全球性的海岸线以前绘制的变化，海湾的关系，悬崖解释为沿海悬崖。然而，自早期以来，维京人的研究，有一个集中的评估存在或不存在的沿海建筑地貌，如障碍脊和沙嘴，位于或附近的地图"海岸线"。这种构造地貌通常与地球上的海岸侵蚀特征有关，因此需要在火星上进行详细的搜索。对位于Chryse Planitia/Arabia Terra区域（北纬10 °至44 °;东经300 °至0 °）和Isidis Planitia区域（北纬0 °至30 °;东经70 °至105 °）内两条"海岸线"上或附近的所有现有THEMIS维斯和MOC NA图像进行了检查，以寻找任何可以合理地被视为候选海岸山脊的特征。此外，原始MOLA配置文件被用来与差分全球定位系统的配置文件开发的技术在陆地古海岸线，在这些相同的区域搜索沿海山脊。在447个THEMIS维斯和735个MOC NA图像中，只有4个候选者被观察到被合理地解释为海岸山脊;在MOLA剖面中没有观察到候选海岸山脊。这种候选特征的极度缺乏表明了火星低地存在水体的五种可能情况之一：（1）没有海洋存在到先前绘制的“海岸线”的水平;（2）海洋存在，但波浪作用，负责建设沿海地貌的主要因素，是最小的或不存在的;（3）海洋存在，但沉积物输入不足以形成海岸沉积物;（4）海洋存在，但很容易冻结，并随着时间的推移升华;最后（5）海洋存在，海岸地貌被建造，但在它们形成后的时间里，它们几乎都被侵蚀了。
The case for an ocean having once occupied the northern lowlands of Mars has largely been based indirectly on the debouching of the outflow channels into the lowlands, and directly on erosional features along the margins of the lowlands interpreted to be the result of wave action. Two global shorelines were previously mapped from albedo variation, embayment relationships, and scarps interpreted as coastal cliffs. However, not since the early, Viking-based studies, has there been a focused assessment of the presence or absence of coastal constructional landforms such as barrier ridges and spits, located on or near the mapped “shorelines.” Such constructional landforms are typically found in association with coastal erosional features on Earth, and therefore warrant a detailed search for their presence on Mars. All presently available THEMIS VIS and MOC NA images located on or near either of the two “shorelines,” within the Chryse Planitia/Arabia Terra region (10° to 44° N; 300° to 0° E) and the Isidis Planitia region (0° to 30° N; 70° to 105° E), were examined in search of any features that could reasonably be considered candidate coastal ridges. Additionally, raw MOLA profiles were used in conjunction with a technique developed from Differential Global Positioning System profiles across terrestrial paleo-shorelines, to search for coastal ridges throughout these same regions. Out of 447 THEMIS VIS and 735 MOC NA images examined, only four candidates are observed that are plausibly interpreted as coastal ridges; no candidate coastal ridges are observed in the MOLA profiles. This overwhelming paucity of candidate features suggests one of five possible scenarios in terms of the existence of standing bodies of water within the martian lowlands: (1) No ocean existed up to the level of either of the previously mapped “shorelines”; (2) An ocean existed, however wave action, the primary agent responsible for construction of coastal landforms, was minimal to non-existent; (3) An ocean existed, but sediment input was not significant enough to form coastal deposits; (4) An ocean existed, but readily froze, and over time sublimated; and lastly (5) An ocean existed and coastal landforms were constructed, but in the intervening time since their formation they have nearly all been eroded away.