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- Fretted terrain is a type of surface feature common to certain areas of Mars and was discovered in Mariner 9 images. It lies between two different types of terrain. The surface of Mars can be divided into two parts: low, young, uncratered plains that cover most of the northern hemisphere, and high-standing, old, heavily cratered areas that cover the southern and a small part of the northern hemisphere. Between these two zones is a region called the Martian dichotomy and parts of it contain fretted terrain. This terrain contains a complicated mix of cliffs, mesas, buttes, and straight-walled and sinuous canyons. It contains smooth, flat lowlands along with steep cliffs. The scarps or cliffs are usually 1 to 2 km high. Channels in the area have wide, flat floors and steep walls. Fretted terrain shows up in northern Arabia, between latitudes 30°N and 50°N and longitudes 270°W and 360°W, and in Aeolis Mensae, between 10 N and 10 S latitude and 240 W and 210 W longitude. Two good examples of fretted terrain are Deuteronilus Mensae and Protonilus Mensae. Fretted terrain in Arabia Terra (Ismenius Lacus quadrangle), seems to transition from narrow straight valleys to isolated mesas. Most of the mesas are surrounded by forms that have been given a variety of names: circum-mesa aprons, debris aprons, rock glaciers, and lobate debris aprons. At first, they appeared to resemble rock glaciers on Earth. But scientists could not be sure. Even after the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) took a variety of pictures of fretted terrain, experts could not tell for sure if material was moving or flowing as it would in an ice-rich deposit (glacier). Eventually, proof of their true nature was discovered when radar studies with the Mars Reconnaissance Orbiter showed that they contained pure water ice covered with a thin layer of rocks that insulated the ice. Besides rock-covered glaciers around mesas, the region had many steep-walled valleys with lineations—ridges and grooves—on their floors. The material comprising these valley floors is called lineated valley fill. In some of the best images taken by the Viking Orbiters, some of the valley fill appeared to resemble alpine glaciers on Earth. Given this similarity, some scientists assumed that the lineations on these valley floors might have formed by flow of ice in (and perhaps through) these canyons and valleys. Today it is generally agreed that glacial flow caused the lineations. Fretted terrain in Aeolis Mensae is similar to that of Arabia Terra, but it lacks debris aprons and lineated valley fill. The Medusae Fossae Formation, a friable, layered material that is covered with yardangs surrounds parts of the fretted terrain in Aeolis Mensae. The origin of fretted plateau material is not completely understood. It does seem to contain fine-grained material, and it has an almost total lack of boulders. This material contrasts with most of the Martian surface which is covered with the igneous rock basalt. Basalt breaks into boulders and eventually into sand. It is thought that when plateau material breaks down, the small-sized particles can be easily carried away by the wind. Erosion of plateau material seems to be much faster than other materials on Mars. Research presented in 2018 at a Lunar and Planetary Science Conference in Texas suggested that the erosion that formed fretted terrain was aided by water moving under the surface. (en)
- 锐蚀地形(Fretted terrain) 是火星某些区域共有的一种表面特征并发现于水手9号所拍摄的照片中。它位于两种不同的地形之间，火星表面可分为两部分：覆盖了北半球大部分地区的低矮、年轻、无陨坑的平原；以及覆盖了南半球和一小部分北半球的高耸、古老、陨坑遍布的区域。介于这两种区域间的地区被称为火星分界区，其中部分包含了锐蚀地形。这种地形混杂着悬崖、桌山、地垛群以及直壁和蜿蜒的峡谷，还包含有紧挨陡崖的平坦低地和1-2公里高的陡坡或悬崖，该地区的河谷有宽阔平坦的地表和陡峭的崖壁。锐蚀地形出现在阿拉伯台地北部区北纬30°至50°、西经270°至360°之间；以及埃奥利斯桌山群中北纬10°至南纬10°、西经240°至210°之间，锐蚀地形两个典型的示例是都特罗尼勒斯桌山群和普罗敦尼勒斯桌山群。 阿拉伯高地(伊斯墨诺斯湖区)中的锐蚀地形似乎从狭窄的直谷过渡到孤耸的桌山。大部分桌山周围都环绕着被赋予不同称呼的地貌特征：环台地围裙、岩屑围裙、岩石冰川和舌状岩屑坡等。起初，它们看起来像地球上的岩石冰川，但科学家们尚不敢确定，即使在火星全球勘测者(MGS)和火星轨道器相机(MOC)拍摄了各种锐蚀地形照片后，专家们仍无法确定这些物质是否像富冰沉积物(冰川)那样移动或流动。最终，火星勘测轨道器的雷达研究表明，它们含有纯净的水冰，上面覆盖着一层隔温的薄岩层，从而证明了它们的真实属性。 除了台地周围岩石覆盖的冰川外，该地区还有许多谷底带有线纹楞脊和沟槽的陡峭峡谷，构成谷底的这些材料被称为线状谷底沉积，在海盗号拍摄的一些最好图像中，部分峡谷的沉积物看起来像地球上的阿尔卑斯型冰川。考虑到这种相似性，一些科学家认为这些谷底线纹可能是流入(或是通过)峡谷和山谷中的冰形成的，今天人们已普遍认为是冰川流造成的线纹。 埃奥利斯桌山群中的锐蚀地形与阿拉伯地形相似，但缺少舌状岩屑坡和线状谷底沉积。埃奥利斯桌山群的部分地区被覆盖着雅丹地貌易碎、层状材料的梅杜莎槽沟层所环绕。 锐蚀高原地层的起源目前仍不完全清楚，看起来它确实含有细粒物质，而且几乎完全没有巨砾。这种地层和火星大部分表面覆盖的火成岩玄武岩形成鲜明对比。玄武岩会变成巨石，最后碎成沙子。人们认为，当高原地层物分解时，这些细小的颗粒更容易被风带走，高原地层的侵蚀似乎比火星上的其他地层快得多。2018年在德克萨斯州举行的月球和行星科学会议上发表的研究报告表明，形成锐蚀地形的侵蚀是由地表下的水流推动的。 (zh)
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- Fretted terrain is a type of surface feature common to certain areas of Mars and was discovered in Mariner 9 images. It lies between two different types of terrain. The surface of Mars can be divided into two parts: low, young, uncratered plains that cover most of the northern hemisphere, and high-standing, old, heavily cratered areas that cover the southern and a small part of the northern hemisphere. Between these two zones is a region called the Martian dichotomy and parts of it contain fretted terrain. This terrain contains a complicated mix of cliffs, mesas, buttes, and straight-walled and sinuous canyons. It contains smooth, flat lowlands along with steep cliffs. The scarps or cliffs are usually 1 to 2 km high. Channels in the area have wide, flat floors and steep walls. Fretted terr (en)
- 锐蚀地形(Fretted terrain) 是火星某些区域共有的一种表面特征并发现于水手9号所拍摄的照片中。它位于两种不同的地形之间，火星表面可分为两部分：覆盖了北半球大部分地区的低矮、年轻、无陨坑的平原；以及覆盖了南半球和一小部分北半球的高耸、古老、陨坑遍布的区域。介于这两种区域间的地区被称为火星分界区，其中部分包含了锐蚀地形。这种地形混杂着悬崖、桌山、地垛群以及直壁和蜿蜒的峡谷，还包含有紧挨陡崖的平坦低地和1-2公里高的陡坡或悬崖，该地区的河谷有宽阔平坦的地表和陡峭的崖壁。锐蚀地形出现在阿拉伯台地北部区北纬30°至50°、西经270°至360°之间；以及埃奥利斯桌山群中北纬10°至南纬10°、西经240°至210°之间，锐蚀地形两个典型的示例是都特罗尼勒斯桌山群和普罗敦尼勒斯桌山群。 阿拉伯高地(伊斯墨诺斯湖区)中的锐蚀地形似乎从狭窄的直谷过渡到孤耸的桌山。大部分桌山周围都环绕着被赋予不同称呼的地貌特征：环台地围裙、岩屑围裙、岩石冰川和舌状岩屑坡等。起初，它们看起来像地球上的岩石冰川，但科学家们尚不敢确定，即使在火星全球勘测者(MGS)和火星轨道器相机(MOC)拍摄了各种锐蚀地形照片后，专家们仍无法确定这些物质是否像富冰沉积物(冰川)那样移动或流动。最终，火星勘测轨道器的雷达研究表明，它们含有纯净的水冰，上面覆盖着一层隔温的薄岩层，从而证明了它们的真实属性。 (zh)
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