| has abstract
| - Equatorial layered deposits (ELD’s) have been called interior layered deposits (ILDs) in Valles Marineris. They are often found with the most abundant outcrops of hydrated sulfates on Mars, and thus are likely to preserve a record of liquid water in Martian history since hydrated sulfates are formed in the presence of water. Layering is visible on meter scale, and when the deposits are partly eroded, intricate patterns become visible.The layers in the mound in Gale Crater have been extensively studied from orbit by instruments on the Mars Reconnaissance Orbiter. The Curiosity Rover landed in the crater, and it has brought some ground truth to the observations from satellites. Many of the layers in ELD’s such as in Gale Crater are composed of fine-grained, easily erodible material as are many other layered deposits. On the basis of albedo, erosion patterns, physical characteristics, and composition, researchers have classified different groups of layers in Gale Crater that seem to be similar to layers in other (ELD’s). The groups include: a small yardang unit, a coarse yardang unit, and a terraced unit.Generally, equatorial layered deposits are found ~ ±30° of the equator. Equatorial Layered Deposits appear in various geological settings such as cratered terrains (Arabia Terra, Meridiani Planum), chaotic terrains (Aram Chaos, Aureum Chaos), the Valles Marineris chasmata (and surrounding plateaus), and large impact craters ( Gale, Becquerel, Crommelin).
* Layered terrain, as seen by HiRISE under HiWish program. Location is East of Gale Crater in the Aeolis quadrangle.
* Layers and mounds in Medusae Fossae Formation, as seen by HiRISE under HiWish program Location is East of Gale Crater in the Aeolis quadrangle.
* Layers and a field of small mounds Medusae Fossae Formation, as seen by HiRISE under HiWish program Location is East of Gale Crater in the Aeolis quadrangle.
* Mound showing layers at the base, as seen by HiRISE under HiWish program Location is East of Gale Crater in the Aeolis quadrangle.
* Light toned butte on floor of crater, as seen by HiRISE under HiWish program. Arrows show outcrops of light toned material. Light toned material is probably sulfate-rich and similar to material examined by Spirit Rover, and it once probably covered the whole floor. Other images below show enlargements of the butte. Location is Aureum Chaos in Margaritifer Sinus quadrangle.
* Close up of top of light toned butte, as seen by HiRISE under HiWish program.
* Layered butte in Aureum Chaos, as seen by HiRISE under HiWish program. Some ELD’s have been closely studied in Firsoff Crater. Changes in the level of groundwater seem to be the major factor controlling ELD deposition in and around Firsoff Crater. The layers inside Firsoff and other nearby craters would likely have started with fluid upwelling through fissures and mounds, which later lead to evaporite precipitation. Spring and playa deposits suggest the presence of a hydrological cycle, driving groundwater upwelling on Mars at surface temperatures above freezing.Pictures below show some of the layering in Firsoff Crater, which is a candidate for a rover landing in 2020.
* MOLA map showing Firsoff Crater, Crommelin Crater, and Danielson Crater. These all have equatorial layered deposits . Colors indicate elevations.
* Layers in Firsoff crater with a box showing the size of a football field. Location is Arabia Terra in Oxia Palus quadrangle. Picture taken by HiRISE under HiWish program.
* Layers and faults in Firsoff Crater, as seen by HiRISE under HiWish program. Arrows show one large fault, but there are other smaller ones in the picture.
* Faults and layers in Firsoff Crater, as seen by HiRISE under HiWish program.
* Wide view of layers in Firsoff Crater, as seen by HiRISE under HiWish program.
* Wide view of layers in Firsoff Crater, as seen by HiRISE under HiWish program. Many depositional processes have been proposed to explain Equatorial Layered Deposits (ELDs) formation, such as volcanoes under ice, dust from the air, lake deposits, and mineral deposits from springs. Groundwater may have played an important part in forming layers in many locations. Calculations and simulations show that groundwater carrying dissolved minerals would surface in the same locations that have abundant rock layers. According to these ideas, deep canyons and large craters would receive water coming from the ground. Many craters in the Arabia area of Mars contain groups of layers. Some of these layers may have resulted from climate changes. The tilt of the rotational axis of Mars has repeatedly changed in the past. Some changes are large. Because of these variations of climate, at times the atmosphere of Mars will be much thicker and contain more moisture. The amount of atmospheric dust also has increased and decreased. It is believed that these frequent changes helped to deposit material in craters and other low places. The rising of mineral-rich ground water cemented these materials. The model also predicts that after a crater is full of layered rocks; additional layers will be laid down in the area around the crater. So, the model predicts that layers may also have formed in intercrater regions, and layers in these regions have been observed.Layers can be hardened by the action of groundwater. Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through. When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents. Consequently, layers of dust could not later easily erode away since they were cemented together. On Earth, mineral-rich waters often evaporate forming large deposits of various types of salts and other minerals. Sometimes water flows through Earth's aquifers, and then evaporates at the surface just as is hypothesized for Mars. One location this occurs on Earth is the Great Artesian Basin of Australia. On Earth the hardness of many sedimentary rocks, like sandstone, is largely due to the cement that was put in place as water passed through. Much strong evidence for groundwater cementing materials comes from the results of the Opportunity Rover. Some places, examined by Opportunity such as Endurance, Eagle, and Erebus craters have been found to be where the water table breached the surface., Also, it was discovered that wind-driven currents of water transported sediment at these locations. Small surface cracks are thought to have formed during multiple wetting and drying events, so they are evidence that the groundwater rose and fell. (such as jarosite) in the rocks of Meridiani Planum indicates that acidic fluids were present. These acidic liquids could have been produced when water with dissolved Fe(II) was oxidized as it reached the surface. Hydrologic models predict that groundwater should indeed emerge in the Sinus Meridiani region.
* Butte in Crommelin Crater, as seen by HiRISE under HiWish program. Location is Arabia Terra in Oxia Palus quadrangle.
* Layers in Crommelin Crater, as seen by HiRISE under HiWish program. Location is Oxia Palus quadrangle.
* Layers in Crommelin Crater, as seen by HiRISE under HiWish program. Arrow indicates fault. Location is Oxia Palus quadrangle. (en)
- 赤道层状沉积物（Equatorial layered deposits）英文简称ELD，在水手谷中被称为内部层状沉积物 (ILD)。它们通常被发现是火星上水合硫酸盐露头最丰富的地方，因此，很可能保存有火星液态水的历史记录，因为水合硫酸盐一般是在存在有水的情况下才能形成。在米级尺度上可看到层状地层，当沉积物被部分侵蚀时，复杂的图案变得清晰可见。盖尔撞击坑内土丘中的地层已由火星勘测轨道飞行器上的仪器在轨道上进行了大量的研究，降落在该陨坑中的好奇号漫游车又补充了一些地面真实情况。赤道层状沉积物的许多地层，如盖尔撞击坑中的，与许多其他层状沉积物一样，都由细粒径、易侵蚀的材料组成。根据反照率、侵蚀模式、物理特征和组成成分的不同，研究人员对盖尔坑中似乎与其他陨坑中相似的不同层组进行了分类，它们包括：小型雅丹单元、粗雅丹单元和阶坡单元。赤道层状沉积物通常出现于赤道南北30度范围内的各类地质环境中，如坑洼地形（阿拉伯台地、子午线高原）、混沌地形（阿伦混沌、欧罗姆混沌）、水手谷（及其周边高原）和大型撞击坑（盖尔、贝克勒尔、克罗姆林）。
* HiWish计划下高分辨率成像科学设备显示的埃俄利斯区盖尔撞击坑东面的分层地形。
* HiWish计划下高分辨率成像科学设备显示的埃俄利斯区盖尔撞击坑东面，梅杜莎槽沟层中的分层和土丘。
* HiWish计划下高分辨率成像科学设备显示的埃俄利斯区盖尔撞击坑东面，梅杜莎槽沟层中的分层和丘堆区。
* HiWish计划下高分辨率成像科学设备在埃俄利斯区盖尔陨石坑以东看到的底部显示有分层的丘堆。
* HiWish计划下高分辨率成像科学设备显示的陨坑内浅色的地垛，箭头指示出浅色材料的露头。浅色材料可能富含硫酸盐和类似勇气号探测车检测过的材料，它们可能曾布满整个坑底。下面的其他图片显示珍珠湾区欧罗姆混沌中放大的地垛。
* HiWish计划下高分辨率成像科学设备拍摄的浅色地垛顶部的特写。
* HiWish计划下高分辨率成像科学设备显示的欧罗姆混沌中的层状地垛。 一些赤道层状沉积物已在菲尔索夫陨击坑中被仔细研究过，地下水水位的变化似乎是决定菲尔索夫陨击坑及周围层状沉积物沉积的主要因素。菲尔索夫及附近其他陨坑内的地层很可能是由从裂缝和丘堆中向上涌出的流体开始的，后来导致蒸发岩沉淀。喷泉和干湖沉积物表明存在一种水文循环，当火星地表温度高于冰点时会促使地下水上升。 下面的图片显示了菲尔索夫陨击坑中的一些分层，该陨坑曾是2020年火星车的着陆候选地。
* 显示了菲尔索夫陨击坑、克罗姆林陨击坑和丹尼尔森陨石坑的火星轨道器激光高度计地图，这些陨坑中都有赤道层状沉积物，颜色表示海拔高度。
* HiWish计划下高分辨率成像科学设备显示的欧克西亚沼区阿拉伯台地中菲尔索夫陨击坑内的岩层，方框显示了足球场大小区域。
* HiWish计划下高分辨率成像科学设备显示的菲尔索夫陨击坑的岩层和断层，箭头指示了一道较大的断层，但图中还有其他更小的断层。
* HiWish计划下高分辨率成像科学设备显示的菲尔索夫陨击坑的断层和岩层。
* HiWish计划下高分辨率成像科学设备显示的菲尔索夫陨击坑地层全景图。
* HiWish计划下高分辨率成像科学设备显示的菲尔索夫陨击坑地层全景图。 已提出了许多沉积作用来解释赤道层状沉积物的形成，例如冰下火山、空气中的尘埃、湖泊淤积物和泉水中的矿物沉积。 地下水可能在许多地方的地层形成过程中发挥了重要作用。计算和模拟表明，带有溶解矿物的地下水将在岩层丰富的相同位置出现。根据这种观点，深谷和大陨坑将会接收到来自地下的液态水。火星阿拉伯区的许多陨石坑中都含有一层组。其中一些可能是气候变化造成的，火星自转轴的倾斜度在过去曾多次改变，有些变化很大。由于气候的这种变化，火星大气层有时会更厚，并且含有更多的水分。大气中尘埃的数量也有所增减。据信，这些频繁的变化有助于在陨坑中和其他低洼处沉积物质。富含矿物质地下水的上升使这些物质变得更加坚硬。该模型还预测，当一座陨石坑被层状岩石填满后，则会在该陨坑周边区域形成额外的地层。因此，该模型预测，分层可能也已在陨坑之间的区域形成，并且已在这些区域观察到分层。 地层可通过地下水的作用而变硬，火星地下水可能流动了数百公里，在此过程中它溶解了所经过岩石中的许多矿物质。当地下水浮出在含沉积物的低洼地区时，水在稀薄大气中蒸发，留下矿物质作为沉积物和/或胶结物。由于尘埃层被胶结在一起，因此，以后不会被轻易侵蚀掉。在地球上，富含矿物质的水经常会蒸发形成各种盐和其他矿物的大型沉积物。有时水会流过地球的含水层，然后在地表蒸发，就像对火星假设的那样。地球上发生这种情况的一个地方是澳大利亚的大自流盆地。在地球上，许多沉积岩的硬度，如砂岩，很大程度上是由于水通过后所形成的水泥。 很多表明地下水胶结材料的有力证据来自机遇号的结果，机遇号探测的一些地方，比如坚忍、鹰和厄瑞玻斯撞击坑，已发现是地下水位突破地表的地方。此外，在这些地方还发现了风驱动的水流所运来的沉积物。表面小裂缝被认为是在多次湿润和干燥事件中形成的，因此它们是地下水上升和下降的证据。子午线高原岩石中的硫酸铁（例如黄钾铁矾）表明存在酸性流体。当含有溶解铁（II）的水到达表面被氧化时，可能会产生出这些酸性液体。水文模型预测，子午线湾地区确实会出现地下水。
* HiWish计划下高分辨率成像科学设备显示的欧克西亚沼区阿拉伯台地中克罗姆林陨击坑内的地垛。
* HiWish计划下高分辨率成像科学设备显示的欧克西亚沼区克罗姆林陨击坑内岩层。
* HiWish计划下高分辨率成像科学设备显示的欧克西亚沼区克罗姆林陨击坑内岩层，箭头指示了断层。 (zh)
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