North-south geological differences between the residual polar caps on Mars

Polar processes can be sensitive indicators of global climate, and the geological features associated with polar ice caps can therefore indicate evolution of climate with time. The polar regions on Mars have distinctive morphologic and climatologic features: thick layered deposits, seasonal CO2 frost caps extending to mid latitudes, and near-polar residual frost deposits that survive the summer. The relationship of the seasonal and residual frost caps to the layered deposits has been poorly constrained, mainly by the limited spatial resolution of the available data. In particular, it has not been known if the residual caps represent simple thin frost cover or substantial geologic features. Here we show that the residual cap on the south pole is a distinct geologic unit with striking collapse and erosional topography; this is very different from the residual cap on the north pole, which grades into the underlying layered materials. These findings indicate that the differences between the caps are substantial (rather than reflecting short-lived differences in frost cover), and so support the idea of long-term asymmetry in the polar climates of Mars.     

Magnesium sulphate salts and the history of water on Mars

Recent reports of approximately 30 wt% of sulphate within saline sediments on Mars--probably occurring in hydrated form--suggest a role for sulphates in accounting for equatorial H2O observed in a global survey by the Odyssey spacecraft. Among salt hydrates likely to be present, those of the MgSO4*nH2O series have many hydration states. Here we report the exposure of several of these phases to varied temperature, pressure and humidity to constrain their possible H2O contents under martian surface conditions. We found that crystalline structure and H2O content are dependent on temperature-pressure history, that an amorphous hydrated phase with slow dehydration kinetics forms at <1% relative humidity, and that equilibrium calculations may not reflect the true H2O-bearing potential of martian soils. Mg sulphate salts can retain sufficient H2O to explain a portion of the Odyssey observations. Because phases in the MgSO4*nH2O system are sensitive to temperature and humidity, they can reveal much about the history of water on Mars. However, their ease of transformation implies that salt hydrates collected on Mars will not be returned to Earth unmodified, and that accurate in situ analysis is imperative.     

Perennial water ice identified in the south polar cap of Mars

The inventory of water and carbon dioxide reservoirs on Mars are important clues for understanding the geological, climatic and potentially exobiological evolution of the planet. From the early mapping observation of the permanent ice caps on the martian poles, the northern cap was believed to be mainly composed of water ice, whereas the southern cap was thought to be constituted of carbon dioxide ice. However, recent missions (NASA missions Mars Global Surveyor and Odyssey) have revealed surface structures, altimetry profiles, underlying buried hydrogen, and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide. Here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes, at a resolution of 2 km, during the local summer, when the extent of the polar ice is at its minimum. We observe that this south polar cap contains perennial water ice in extended areas: as a small admixture to carbon dioxide in the bright regions; associated with dust, without carbon dioxide, at the edges of this bright cap; and, unexpectedly, in large areas tens of kilometres away from the bright cap.     

Subsurface water and clay mineral formation during the early history of Mars

Clay minerals, recently discovered to be widespread in Mars's Noachian terrains, indicate long-duration interaction between water and rock over 3.7 billion years ago. Analysis of how they formed should indicate what environmental conditions prevailed on early Mars. If clays formed near the surface by weathering, as is common on Earth, their presence would indicate past surface conditions warmer and wetter than at present. However, available data instead indicate substantial Martian clay formation by hydrothermal groundwater circulation and a Noachian rock record dominated by evidence of subsurface waters. Cold, arid conditions with only transient surface water may have characterized Mars's surface for over 4 billion years, since the early-Noachian period, and the longest-duration aqueous, potentially habitable environments may have been in the subsurface.     

Thermal history of Mars inferred from orbital geochemistry of volcanic provinces

Reconstruction of the geological history of Mars has been the focus of considerable attention over the past four decades, with important discoveries being made about variations in surface conditions. However, despite a significant increase in the amount of data related to the morphology, mineralogy and chemistry of the martian surface, there is no clear global picture of how magmatism has evolved over time and how these changes relate to the internal workings and thermal evolution of the planet. Here we present geochemical data derived from the Gamma Ray Spectrometer on board NASA's Mars Odyssey spacecraft, focusing on twelve major volcanic provinces of variable age. Our analysis reveals clear trends in composition that are found to be consistent with varying degrees of melting of the martian mantle. There is evidence for thickening of the lithosphere (17-25?km?Gyr(-1)) associated with a decrease in mantle potential temperature over time (30-40?K?Gyr(-1)). Our inferred thermal history of Mars, unlike that of the Earth, is consistent with simple models of mantle convection.     

夹皮沟金矿地质与采金技术简史

介绍了夹皮沟矿区地理位置、地质特征、开采历史的变迁和采金技术的发展.根据目前对该矿勘探、勘测资料,未来开采的前景可观.加大科技探矿的投入,挖掘黄金资源,为21世纪的后续发展储备资金十分必要.     

夹皮沟金矿地质与采金技术简史

介绍了夹皮沟矿区地理位置、地质特征、开采历史的变迁和采金技术的发展．根据目前对该矿勘探、勘测资料，未来开采的前景可观．加大科技探矿的投入，挖掘黄金资源，为21世纪的后续发展储备资金十分必要．     

火星中的水和生命

科学家由于在对火星的观察中观察到水存在的信息，因而进一步考虑研究在火星中存在生命的可能性，这一研究是科学上十分重要而有意义的。     

多旋回沉积盆地地温场与烃源岩演化--以苏北盆地为例

目的 恢复苏北盆地古地温场，进行热演化史研究，确定主要的生烃时期。方法 在盆地演化史分析的基础上，应用镜质体反射率、包裹体分析等技术。结果 苏北盆地新生代具有多旋回盆地演化的特点，地温梯度呈降低趋势，古近纪40～45℃／km，新近纪30℃／km左右；烃源岩演化经历了早期生烃、中期生烃停滞、晚期生烃3个阶段。结论 烃源岩成熟度主要受古地温场的控制，而与现今地温梯度无关；渐新世持续18Ma的三垛抬升运动是造成苏北盆地烃源岩演化程度低的主要原因。     

Weather and climate on Mars.

Imagine a planet very much like the Earth, with similar size, rotation rate and inclination of rotation axis, possessing an atmosphere and a solid surface, but lacking oceans and dense clouds of liquid water. We might expect such a desert planet to be dominated by large variations in day-night and winter-summer weather. Dust storms would be common. Observations and simulations of martian climate confirm these expectations and provide a wealth of detail that can help resolve problems of climate evolution.     

火星盐类研究进展

 因携带水相关地质过程及环境的丰富信息,进而与生命起源密切相关,行星盐类研究受到大量科研工作者的关注。好奇号登陆之后,火星盐类研究取得了一些新进展。例如,在着陆区泥岩中发现了黄钾铁矾;在泥岩及泥岩砂岩的不整合接触面发现了石膏脉;在风沉积及原位沉积岩中发现了硝酸盐。此外,通过遥感手段,还发现火星新出现的斜坡沟渠可能是由含高氯酸盐高浓卤水冲击形成的。这些新进展再次表明了盐类对于火星科学的重要性。结合已有研究,凝练了火星盐类研究存在的重要科学问题,展望了中国未来火星探测研究。     

Discovery of an aurora on Mars

In the high-latitude regions of Earth, aurorae are the often-spectacular visual manifestation of the interaction between electrically charged particles (electrons, protons or ions) with the neutral upper atmosphere, as they precipitate along magnetic field lines. More generally, auroral emissions in planetary atmospheres "are those that result from the impact of particles other than photoelectrons" (ref. 1). Auroral activity has been found on all four giant planets possessing a magnetic field (Jupiter, Saturn, Uranus and Neptune), as well as on Venus, which has no magnetic field. On the nightside of Venus, atomic O emissions at 130.4 nm and 135.6 nm appear in bright patches of varying sizes and intensities, which are believed to be produced by electrons with energy <300 eV (ref. 7). Here we report the discovery of an aurora in the martian atmosphere, using the ultraviolet spectrometer SPICAM on board Mars Express. It corresponds to a distinct type of aurora not seen before in the Solar System: it is unlike aurorae at Earth and the giant planets, which lie at the foot of the intrinsic magnetic field lines near the magnetic poles, and unlike venusian auroras, which are diffuse, sometimes spreading over the entire disk. Instead, the martian aurora is a highly concentrated and localized emission controlled by magnetic field anomalies in the martian crust.     

Dynamics of ice ages on Mars

Unlike Earth, where astronomical climate forcing is comparatively small, Mars experiences dramatic changes in incident sunlight that are capable of redistributing ice on a global scale. The geographic extent of the subsurface ice found poleward of approximately +/-60 degrees latitude on both hemispheres of Mars coincides with the areas where ice is stable. However, the tilt of Mars' rotation axis (obliquity) changed considerably in the past several million years. Earlier work has shown that regions of ice stability, which are defined by temperature and atmospheric humidity, differed in the recent past from today's, and subsurface ice is expected to retreat quickly when unstable. Here I explain how the subsurface ice sheets could have evolved to the state in which we see them today. Simulations of the retreat and growth of ground ice as a result of sublimation loss and recharge reveal forty major ice ages over the past five million years. Today, this gives rise to pore ice at mid-latitudes and a three-layered depth distribution in the high latitudes of, from top to bottom, a dry layer, pore ice, and a massive ice sheet. Combined, these layers provide enough ice to be compatible with existing neutron and gamma-ray measurements.     

城市地质学与城市规划研究探讨

城市是人类文明的结晶,随着经济的发展,近年来城市化进程明显加快,要实现城市的和谐发展,科学合理的城市规划尤为重要。纵观中国城市规划建设过程,在取得令世人瞩目的成就的同时也患上难以解决的"城市病";深入开展城市地质学研究,有助于解决城市规划建设中出现的问题。对城市地质学的研究前沿和城市规划过程中出现的问题进行深入的分析研究,并基于城市地质学之上探讨了如何有效的解决"城市病"的一些措施。     

黄山地质探讨

本文旨在从皖南黄山地区地层的形成分布、岩浆岩体的基本特征和地质构造的展布规律,探讨该区地质基础形成发育的过程和区域构造应力场的关系。     

生物科学史教学情境创设的素材研究

生物科学史是创设教学情境素材的主要来源,因此生物教学中科学史教学情境的创设,在一定程度上决定于对素材的积累与选择.主要对素材分类、收集途径和要求、使用策略进行分析和研究,以期实现生物科学史情境教学的预期效果     

Phyllosilicates on Mars and implications for early martian climate

The recent identification of large deposits of sulphates by remote sensing and in situ observations has been considered evidence of the past presence of liquid water on Mars. Here we report the unambiguous detection of diverse phyllosilicates, a family of aqueous alteration products, on the basis of observations by the OMEGA imaging spectrometer on board the Mars Express spacecraft. These minerals are mainly associated with Noachian outcrops, which is consistent with an early active hydrological system, sustaining the long-term contact of igneous minerals with liquid water. We infer that the two main families of hydrated alteration products detected-phyllosilicates and sulphates--result from different formation processes. These occurred during two distinct climatic episodes: an early Noachian Mars, resulting in the formation of hydrated silicates, followed by a more acidic environment, in which sulphates formed.