Loess: The Yellow Earth

A wind-deposited silt forming large deposits in China and middle America, loess is the basis of much grade-one agricultural land.     

古地磁:从地球到火星

古地磁学是一门典型的交叉学科,通过综合地质学、地球物理学、环境科学等学科相关方法,分析天然样品中记录的磁学信息,深入研究地磁场演化、地球动力学过程、古环境与古气候演化等.自20世纪中叶以来,古地磁学在各研究领域得到快速发展,通过进一步与其他学科交叉,衍生出诸多新兴方向.首先回顾了古地磁学的发展历史与基础研究领域.在此基础上,重点介绍了高精度卫星磁测与相关研究新领域、月球与火星磁学研究的新进展.同时,对古地磁学与高精度磁测等方法集成在地磁场演化、板块构造、深部结构、月球磁场演化、火星磁场及环境演化等方面的综合应用进行了讨论.最后,对古地磁学未来的潜在研究方向进行了展望.      

Saltation threshold on Earth, Mars and Venus

New formulations valid for wide ranges of particle diameter and density and gas density are presented for prediction of saltation threshold speed for small particles. A low-air-density wind tunnel was used to extend the range of previous investigations and to separate the effects of Reynolds number and interparticle forces of cohesion. The new formulations are used to predict saltation threshold for atmospheric conditions on the surface of the Earth, Mars, and Venus.     

A Comparative Analysis of Evaporate Sediments on Earth and Mars：Implications for the Climate Change on Mars

The knowledge of Martian salts has gone through substantial changes during the past decades. In the 70th of last century, Viking landers have noticed the existence of salts on Mars. Several salt species have been suggested from then on, such as sulfates and chlorides. However, their origin was a mystery due to the lack of observations. The recent explorations and related studies at the beginning of this century revealed that the crustal composition of Mars is similar to that of Earth, and it was hypothesized that almost one third of Martian surface was covered by oceans and lakes in the early stage of Mars. The huge water bodies may have dissolved a large quantity of ions from Martian primary rocks during the whole Noachian and Hesperian epoch. After the enormous drought event happened during the late Hesperian and the early Amazonian, these dissolved ions have formed huge salts deposits and most of them were preserved on Mars until today. To date, carbonates, sulfates, chlorides have all been detected by orbital remote sensing and by landers and rovers. However, the salt mineral assemblages on Mars seems to have some differences from those on Earth, e.g., rich in sulfates and lack of massive carbonates. To explain this difference, we propose that most of the surface carbonates precipitated from the ancient oceans may have been dissolved by the later ubiquitous acidic fluids originated from the global volcanism in the Hesperian era, and formed the enormous sulfate deposits as detected, and this hypothesis seems to be supported by the evidence that most of the sulfate deposits distribute around the Tharsis volcanic province while the survived carbonates located far from it. This process can release most of the carbon on Mars to the atmosphere in the form of CO2 and then be erased by the late heavy bombardments, which might have profound influence on the climate change happened in the Hesperian age. The positive correlation between the GRS results of the potassium distributions and the distribution of chlorides on Mars, together with the high Br concentration measured from the evaporate sediments at two Mars exploration rover landing sites, indicate that the brines in the regions where the chlorides deposited may have reached the stage for potassium salts deposition, thus we propose for the first time that potassium salts deposits might be prevalent in these regions.     

A Comparative Analysis of Evaporite Deposition on Earth and Mars

<正>In this paper,the authors give a brief review of recent observations and studies on Martian salts.On the basis of the comparison of salt sediments on Earth and Mars,the authors propose that potassium salts might be widespread on Martian surface and subsurface.Besides,the authors found a positive correlation between the GRS results of the po-     

地球同火星蒸发岩沉积的对比

迄今为止,人类已经通过火星轨道探测器、火星着陆器及火星漫游车在火星上发现了碳酸盐、硫酸盐及氯化物等一 系列的盐类矿物,尽管整体上火星盐类矿物组合与地球上基本一致,但在许多细节方面还是和地球上有所不同。文中首先 对于火星盐类认知的现状作了简要综述;基于地球火星蒸发盐沉积及成盐作用规律的对比,预测火星表面及次表面可能存 在着广泛分布的钾盐;此外,发现火星轨道伽玛光谱仪所获的火星表面 K 的分布与火星表面已探测到的氯化物的分布有比 较强的相关性,喻示火星表面氯化物沉积地区的卤水浓度已经接近或达到钾盐形成的条件,同时指出这些地区存在钾盐的 可能性很大。     

Foreword: Magma generation and evolution in the Earth

A VOLUME IN HONOUR OF THE WORK OF MICHAEL J. O'HARA, ON THE OCCASION OF HIS 70TH BIRTHDAY The 20th century was eventful inall areas of Earth Science. Continental drift and sea-floorspreading became embodied in the theory of plate tectonics,isotopically heterogeneous mantle was recognized as a by-productof plate tectonics, large igneous provinces were identifiedas possibly originating from mantle plumes - the list goes on.One thing these revolutions have in common is the process ofscientific debate - which Mike O'Hara has stimulated vigorouslyin the field of     

Giant Circumferential Dyke Swarms on Earth: Possible Analogues of Coronae on Venus and Similar Features on Mars

正Venusian coronae are large(60-2600 km diameter)tectono-magmatic features characterized by quasi-circular graben-fissure systems and topographic features such as a central dome,central depression,circular rim or circular     

Glacial-interglacial changes in dust deposition on the Chinese Loess Plateau

The Chinese Loess Plateau (CLP) contains an extensive record of aeolian deposition through multiple glacial–interglacial cycles. Independent chronologies based on pedostratigraphy, magnetic susceptibility, radiocarbon and luminescence dating were developed for 79 sites and used to estimate aeolian mass accumulation rates (MARs) for marine isotope stages 1–5. The regional median value of MAR for Stage 2 is 310 g/m²/yr compared to an estimate of 65 g/m²/yr for Stage 5. Estimated MARs from individual sites for Stage 2 are approximately 4.3 times greater than MARs for Stage 5 and 2.1 times greater than for Stage 1. MAR values at individual sites are consistently highest in the northwest and lowest in the southwest of the CLP during all marine isotope stages. MARs estimated on sections through loess terraces are consistently higher than MAR estimates at other sites, indicating that local recycling of loess material from exposed river valley deposits has been significant throughout the last 130 kyr. Although the spatial and temporal patterns in MAR are robust, there are uncertainties about the magnitude of these changes due to (a) lack of bulk density measurements and uncertainties in the chronologies for individual sites, (b) site and chronological biases in the sampling used to derive regional estimates, and (c) the unquantified nature of human impact on accumulation rates during the late Holocene. Nevertheless, the records from the CLP pose a number of challenges which could be addressed by numerical models of the palaeo-dust cycle.     

Acidification of Earth: An assessment across mechanisms and scales

In this review article, anthropogenic activities that cause acidification of Earth’s air, waters, and soils are examined. Although there are many mechanisms of acidification, the focus is on the major ones, including emissions from combustion of fossil fuels and smelting of ores, mining of coal and metal ores, and application of nitrogen fertilizer to soils, by elucidating the underlying biogeochemical reactions as well as assessing the magnitude of the effects. These widespread activities have resulted in (1) increased CO₂ concentration in the atmosphere that acidifies the oceans; (2) acidic atmospheric deposition that acidifies soils and bodies of freshwater; (3) acid mine drainage that acidifies bodies of freshwater and groundwaters; and (4) nitrification that acidifies soils. Although natural geochemical reactions of mineral weathering and ion exchange work to buffer acidification, the slow reaction rates or the limited abundance of reactant phases are overwhelmed by the onslaught of anthropogenic acid loading. Relatively recent modifications of resource extraction and usage in some regions of the world have begun to ameliorate local acidification, but expanding use of resources in other regions is causing environmental acidification in previously unnoticed places. World maps of coal consumption, Cu mining and smelting, and N fertilizer application are presented to demonstrate the complex spatial heterogeneity of resource consumption as well as the overlap in acidifying potential derived from distinctly different phenomena. Projected population increase by country over the next four decades indicates areas with the highest potential for acidification, so enabling anticipation and planning to offset or mitigate the deleterious environmental effects associated with these global shifts in the consumption of energy, mineral, and food resources.     

Evidence for a simple pathway to maghemite in Earth and Mars soils

Soil magnetism is greatly influenced by maghemite (γ-Fe₂O₃), the presence of which is usually attributed to the following: (1) heating of goethite in the presence of organic matter; (2) oxidation of magnetite (Fe₃O₄); or (3) dehydroxylation of lepidocrocite (γ-FeOOH). Formation of the latter two minerals in turn requires the presence of Fe(II) in the system. No laboratory experiment or soil study to date has shown whether maghemite can form from ferrihydrite, a poorly crystalline Fe(III) oxide [∼Fe_4.5(O,OH,H₂O)_13.5], below 250°C. However, ferrihydrite is the usual precursor of goethite (α-FeOOH) and hematite (α-Fe₂O₃), the most frequently occurring crystalline Fe(III) oxides in soils. Here is presented in vitro evidence that ferryhidrite can partly transform into maghemite at 150°C. This transformation occurs upon aging of ferrihydrite precipitated in the presence of phosphate or other ligands capable of ligand exchange with Fe-OH surface groups. This maghemite coexists with hematite and is a transient phase in the transformation of ferrihydrite to hematite, which is apparently stabilized by the adsorbed ligands. Its particle size is small (10 to 30 nm), and its X-ray diffraction pattern exhibits superstructure reflections. The possible formation of maghemite in Mars and in different Earth soils can partly be explained in the light of this pathway with minimal ad hoc assumptions.     

Tooting crater: Geology and geomorphology of the archetype large,fresh, impact crater on Mars

The 27.2 km diameter Tooting crater is the best preserved young impact crater of its size on Mars. It offers an unprecedented opportunity to study impact-related phenomena as well the geology of the crust in the Amazonis Planitia region of Mars. For example, the nearly pristine condition enables the partial reconstruction of the sequence of events for crater formation, as well as facilitates a comparison to deposits seen at the Ries crater in Germany. High-resolution images taken by the High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) on the Mars Reconnaissance Orbiter spacecraft have revealed a wealth of information on the distribution of features within the crater and beyond the rim: a large central peak, pitted material on the floor and terrace blocks, lobate flows interpreted to be sediment flows, impact melt sheets, four discrete layers of ejecta, and an asymmetric secondary crater field. Topographic data derived from the Mars Orbiter Laser Altimeter (MOLA) and stereo HiRISE and CTX images show that the central peak is ～1100 m high, the lowest point of the crater floor is 1274 m below the highest part of the rim, and the crater rim has ～600 m of variability around its perimeter. Layering within the cavity walls indicates ～260 m of structural uplift of the target material, which constitutes ～35% of the total relief of the rim. Abundant evidence is found for water flowing down the cavity walls, and on the surface of the ejecta layers, both of which took place sometime after the impact event. Thickness measurements of the ejecta layers reveal that the continuous blanket is remarkably thin (～3–5 m) in some places, and that the distal ramparts may be ～60 m high. Crater counts made on the ejecta layers indicate a model age of <3 Ma for the formation of Tooting crater, and that the target rocks have a model age of ～240–375 Ma. It is therefore possible that this may be the source of certain basaltic shergottite meteorites ejected at ～2.8 Ma that have crystallization ages which are comparable to those of the basaltic lava flows that formed the target materials for this impact event. The geology and geomorphology of Tooting crater may help in the interpretation of older large impact craters on Mars, as well as the potential role of target volatiles in the impact cratering process.     

地震机理的地球系统科学研究及预测实践

本文提出了一个新的地震机理模型:高温高压高导低速流变体震源腔(简称震源腔)与闭锁断层组合模型。高温高压下的软流圈物质在复杂相变空间中,受到温度场中的异重流作用和受迫振动作用而形成深源震源腔。随着软流圈物质上涌, 幔汁在温度差和压力差驱使下,涌入地壳中的物理空间,形成浅源地震震源腔。由于温度升高使得腔体内岩石部分熔融或全部熔融,释放出大量气液流体,拓展腔体空间范围,同时提升腔体内压。当腔体内部有效压力(即内压与上覆地壳压力之差)达到腔体边缘或者上方与脆性活动断层交会部位的岩石破坏强度时,震源腔便进入临界状态。当软流圈物质上涌继续向腔体内供能,或者由于星体连线在震源区造成触发作用,便引起震源腔的隐蔽爆炸,即隐爆,释放腔体内部积累的能量,同时释放区域构造应力场作用于闭锁断层积累的应变能。 腔体隐爆释放能量与腔体规模正相关。闭锁断层释放应变能与闭锁断层规模、闭锁区大小以及区域构造应力场强度相关。震源腔与脆性活动断层交会部位,是潜在震源位置。多年观测资料表明,震源腔从进入临界状态到隐爆,一般经历1~13天,平均7天。长期观测表明,潜在震中区在震前经常出现干旱、气温升高、海温升高、大量水汽释放等异常现象。通过超低频地震仪监测、重力波作用于水汽形成的地震云的观测、次声波的监测、卫星重力异常反映的高程面垂向震荡监测、以及地基卫星导航系统地面升降监测等,都显示出震源腔进入临界状态后的胀缩震荡引起震中及其外围地面的垂向振动。文中还给出了震源腔体隐爆遗迹的直接证据。     

The split fate of the early Earth,Mars, Venus,and Moon

Plate tectonics shaped the Earth, whereas the Moon is a dry and inactive desert, Mars probably came to rest within the first billion years of its history, and Venus, although internally very active, has a dry inferno for its surface. Here we review the parameters that determined the fates of each of these planets and their geochemical expressions. The strong gravity field of a large planet allows for an enormous amount of gravitational energy to be released, causing the outer part of the planetary body to melt (magma ocean), helps retain water on the planet, and increases the pressure gradient. The weak gravity field and anhydrous conditions prevailing on the Moon stabilized, on top of its magma ocean, a thick buoyant plagioclase lithosphere, which insulated the molten interior. On Earth, the buoyant hydrous phases (serpentines) produced by reactions between the terrestrial magma ocean and the wet impactors received from the outer solar system isolated the magma and kept it molten for some few tens of million years. The planets from the inner solar system accreted dry: foundering of wet surface material softened the terrestrial mantle and set the scene for the onset of plate tectonics. This very same process also may have removed all the water from the surface of Venus and added enough water to its mantle to make its internal dynamics very strong and keep the surface very young. Because of a radius smaller than that of the Earth, not enough water could be drawn into the Martian mantle before it was lost to space and Martian plate tectonics never began. The radius of a planet is therefore the key parameter controlling most of its evolutional features.     

Highly siderophile elements in the Earth, Moon and Mars: Update and implications for planetary accretion and differentiation

The highly siderophile elements (HSE) pose a challenge for planetary geochemistry. They are normally strongly partitioned into metal relative to silicate. Consequently, planetary core segregation might be expected to essentially quantitatively remove these elements from planetary mantles. Yet the abundances of these elements estimated for Earth's primitive upper mantle (PUM) and the martian mantle are broadly similar, and only about 200 times lower than those of chondritic meteorites. In contrast, although problematic to estimate, abundances in the lunar mantle may be more than twenty times lower than in the terrestrial PUM. The generally chondritic Os isotopic compositions estimated for the terrestrial, lunar and martian mantles require that their long-term Re/Os ratios were within the range of chondritic meteorites. Further, most HSE in the terrestrial PUM also appear to be present in chondritic relative abundances, although Ru/Ir and Pd/Ir ratios are slightly suprachondritic. Similarly suprachondritic Ru/Ir and Pd/Ir ratios have also been reported for some lunar impact melt breccias that were created via large basin forming events.Numerous hypotheses have been proposed to account for the HSE present in Earth's mantle. These hypotheses include inefficient core formation, lowered metal-silicate D values resulting from metal segregation at elevated temperatures and pressures (as may occur at the base of a deep magma ocean), and late accretion of materials with chondritic bulk compositions after the cessation of core segregation. Synthesis of the large database now available for HSE in the terrestrial mantle, lunar samples, and martian meteorites reveals that each of the main hypotheses has flaws. Most difficult to explain is the similarity between HSE in the Earth's PUM and estimates for the martian mantle, coupled with the striking differences between the PUM and estimates for the lunar mantle. More complex, hybrid models that may include aspects of inefficient core formation, HSE partitioning at elevated temperatures and pressures, and late accretion may ultimately be necessary to account for all of the observed HSE characteristics. Participation of aspects of each process may not be surprising as it is difficult to envision the growth of a planet, like Earth, without the involvement of each.     

Migration and speciation transformation mechanisms of mercury in undercurrent zones of the Tongguan gold mining area,Shaanxi Loess Plateau and impact on the environment

In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment, the field in-situ infiltration test and laboratory test were carried out in three typical sections of river-side loess, alluvial and proluvial strata in Tongguan gold mining area of Shaanxi Province, and the following results were obtained: (1) The source of Hg in subsurface flow zone is mainly caused by mineral processing activities; (2) the subsurface flow zone in the study area is in alkaline environment, and the residual state, iron and manganese oxidation state, strong organic state and humic acid state of mercury in loess are equally divided in dry and oxidizing environment; mercury in river alluvial or diluvial strata is mainly concentrated in silt, tailings and clayey silt soil layer, and mercury has certain stability, and the form of mercury in loess is easier to transform than the other two media; (3) under the flooding condition, most of mercury is trapped in the silt layer in the undercurrent zone where the sand and silt layers alternate with each other and the river water and groundwater are disjointed, and the migration capacity of mercury is far less than that of loess layer and alluvial layer with close hydraulic connection; (4) infiltration at the flood level accelerates the migration of pollutants to the ground; (5) the soil in the undercurrent zone is overloaded and has seriously exceeded the standard. Although the groundwater monitoring results are safe this time, relevant enterprises or departments should continue to pay attention to improving the gold extraction process, especially vigorously rectify the small workshops for illegal gold extraction and the substandard discharge of the three wastes, and intensify efforts to solve the geological environmental problems of mines left over from history. At present, the occurrence form of mercury in the undercurrent zone is relatively stable, but the water and soil layers have been polluted. The risk of disjointed groundwater pollution can not be ignored while giving priority to the treatment of loess and river alluvial landform areas with close hydraulic links. The research results will provide a scientific basis for water conservancy departments to groundwater prevention and control in water-deficient areas of the Loess Plateau.     

The contribution of sulphur dioxide from ablating micrometeorites to the atmospheres of Earth and Mars

Atmospheric composition is a key control on climate and the habitability of planetary surfaces. Ablation of infalling micrometeorites has been recognised as one way in which atmospheric chemistry can be changed, especially at times in solar system history when the infall rates of exogenous material were high. Despite its potential to influence climate and habitability, extraterrestrial sulphur dioxide is currently an unquantified contribution to the atmospheres of the terrestrial planets. We have used flash pyrolysis to simulate the atmospheric entry of micrometeorites and Fourier-transform infrared spectroscopy to identify and quantify the sulphur dioxide produced from the carbonaceous meteorites Orgueil (CI1), ALH 88045 (CM1), Cold Bokkeveld (CM2), Murchison (CM2) and Mokoia (CV3). We have used this approach to understand the introduction of sulphur dioxide to the atmospheres of Earth and Mars from infalling micrometeorites. Sulphates, present in carbonaceous chondrites at a few wt.%, are resistant to thermal decomposition, limiting the yields of sulphur dioxide from unmelted micrometeorites. Infalling micrometeorites are a minor source of present-day sulphur dioxide on Earth and Mars, calculated to be up to around 2400 tonnes and about 350 tonnes, respectively. During the Late Heavy Bombardment (LHB), the much greater infall rates of micrometeoritic dust are calculated to be associated with average production rates of sulphur dioxide of around 20 Mt yr⁻¹ for the early Earth and 0.5 Mt yr⁻¹ for early Mars, for a LHB of 100 Myr. These rates of delivery of sulphur dioxide at high altitudes would have reduced the solar energy reaching the surfaces of these planets, via scattering of sunlight by stratospheric sulphate aerosols, and may have had detrimental effects on developing biospheres by promoting cooler climates and reducing the probability of liquid water on planetary surfaces.     

Space weather hazards and their impact on human cardio-health state parameters on Earth

Recent multi-disciplinary heliobiological and biometeorological researches reveal that the human organism is sensitive to environmental physical activity changes and reacts to them through variations of the physiological parameters of the human body. In this study, electrocardiograms of functionally healthy persons, who were digitally registered at the Laboratory of Heliobiology located in the Medical Centre INAM (Baku, Azerbaijan), were studied in relation to different levels of cosmic ray activity and geomagnetic field disturbances. In total, 1,673 daily digital data of heart rate values and time series of beat-to-beat heart rate intervals (RR intervals) were registered for the time period July 15, 2006?CMarch 31, 2008, which includes the period of December 2006, when intense cosmic ray events and strong geomagnetic disturbances occurred. The statistical significance of the influence of geomagnetic activity levels and cosmic ray intensity variations on heart rate and RR intervals was estimated. Results revealed that heart rate increase and RR intervals variations were more pronounced for high levels of geomagnetic activity and large cosmic ray intensity decreases, whereas very small or even minimum cosmic ray intensity variations did not affect heart rate dynamics. Moreover, heart rate increased on the days before, during and after geomagnetic storms with high intensities and on the days preceding, and following cosmic ray intensity decreases.     

The youngest big impact on Earth deduced from geological and historical evidence

The comparison of events that followed the great impact at the Cretaceous/Tertiary boundary with those contained within the Flood myths suggests an analogous cosmic cause. This paper proposes that there is geological evidence to support this thesis which is also indicated by a careful analysis of the natural phenomena described in Flood traditions. The time, the sites, the cause, the detailed course of the events and the consequences of this catastrophe can hope to be reconstructed.     

黄土高原土壤有机碳固存机制研究进展

黄土高原土层深厚, 蕴藏着大量的土壤有机碳, 由于植被自然生长和生态建设等因素, 黄土高原生态系统发挥了、并在未来持续发挥重要的碳汇作用。在"双碳目标"的重大国家战略背景下, 黄土高原土壤碳汇效应将迎来重大的转机和严峻的挑战。鉴于此, 首先回顾了黄土高原植被恢复进程和土壤的固碳效应, 聚焦植被恢复过程中土壤有机碳固存这一核心过程, 基于土壤物理、化学和生物学的固碳机制和原理, 并结合土壤"微生物碳泵"核心调控理论, 论述了黄土高原植被恢复过程中土壤有机碳的固定过程, 同时概括和总结了土壤有机碳固定的驱动因素; 最后, 对黄土高原土壤碳固存所存在的问题和挑战进行了展望, 为黄土高原乃至我国陆地生态系统土壤碳汇功能、生态效益提升具有重大意义。