کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1773283 | 1523562 | 2014 | 25 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Comprehensive analysis of glaciated martian crater Greg
ترجمه فارسی عنوان
تجزیه و تحلیل جامع از گریس گودال مریخ یخ زده
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
علوم فضا و نجوم
چکیده انگلیسی
The 66-km diameter martian crater, Greg, east of Hellas, hosts various distinctive features, including dendritic valleys filled with chevron-textured masses (south wall), and lobate tongues a few kilometers long (north wall). We analyze these features by various quantitative techniques to illuminate martian geologic and climatic history. Crater retention model ages indicate that Greg is at least 1-3 Gy old, but surface layers of mantles and glacial features are orders of magnitude younger. Properties of the dendritic valleys, combined with climate models, suggest that fluvial activity began under a thicker, warmer atmosphere, soon after the crater's formation. The oldest exposed fluvial systems have surface crater retention ages of a few hundred My, indicating runoff in recent geologic time. Much of Greg is covered by ice-rich mantle deposits, for which we infer gradual accumulation and depths of order 30-85 m; they mask pre-existing landforms. The lobate tongues are interpreted as glaciers with mean slope of 10.2 ± 2.3° and average thickness of 33 ± 19 m. Our calculations and data suggest that these glaciers were originally ice-rich and that their surface layers have been depleted by volatile loss. The glaciers probably formed when ice-rich mantle deposits reached critical thickness and flowed downhill. The top 5-10 m of the mantle and glaciers show crater survival times of order a few My to â¼15 My, which, remarkably, is the time since the last 1-4 episodes of obliquity >45°. Global climate models affirm that Greg lies in one of two non-polar areas with extremes of ice deposition during high-obliquity epochs. This match with observations supports the use of such models in studies of planetary climate change.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Icarus - Volume 228, 15 January 2014, Pages 96-120
Journal: Icarus - Volume 228, 15 January 2014, Pages 96-120
نویسندگان
William K. Hartmann, Veronique Ansan, Daniel C. Berman, Nicolas Mangold, François Forget,