A volcanic environment for bedrock diagenesis at Meridiani Planum on Mars

Exposed bedrocks at Meridiani Planum on Mars display chemical and mineralogical evidence suggesting interaction with liquid water. On the basis of morphological observations as well as high abundances of haematite and sulphate minerals, the rocks have been interpreted as sediments that were deposited in a shallow body of briny water with subsequent evaporation leaving behind the sulphate minerals. The iron-sulphur mineralization at Meridiani has also been inferred to be analogous to that produced during oxidative weathering of metal sulphide minerals, such as occurs at acid mine drainage sites. Neither of these interpretations, however, is consistent with the chemical composition of the rocks. Here we propose an alternative model for diagenesis of Meridiani bedrock that involves deposition of volcanic ash followed by reaction with condensed sulphur dioxide- and water-bearing vapours emitted from fumaroles. This scenario does not require prolonged interaction with a standing body of surface water and may have occurred at high temperatures. Consequently, the model invokes an environment considerably less favourable for biological activity on Mars than previously proposed interpretations.     

Orbital forcing of the martian polar layered deposits

Since the first images of polar regions on Mars revealed alternating bright and dark layers, there has been speculation that their formation might be tied to the planet's orbital climate forcing. But uncertainties in the deposition timescale exceed two orders of magnitude: estimates based on assumptions of dust deposition, ice formation and sublimation, and their variations with orbital forcing suggest a deposition rate of 10(-3) to 10(-2) cm yr(-1) (refs 5, 6), whereas estimates based on cratering rate result in values as high as 0.1 to 0.2 cm yr(-1) (ref. 7). Here we use a combination of high-resolution images of the polar layered terrains, high-resolution topography and revised calculations of the orbital and rotational parameters of Mars to show that a correlation exists between ice-layer radiance as a function of depth (obtained from photometric data of the images of the layered terrains) and the insolation variations in summer at the martian north pole, similar to what has been shown for palaeoclimate studies of the Earth. For the best fit between the radiance profile and the simulated insolation parameters, we obtain an average deposition rate of 0.05 cm yr(-1) for the top 250 m of deposits on the ice cap of the north pole of Mars.     

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。     

Geochemical evidence for magmatic water within Mars from pyroxenes in the Shergotty meteorite

Observations of martian surface morphology have been used to argue that an ancient ocean once existed on Mars. It has been thought that significant quantities of such water could have been supplied to the martian surface through volcanic outgassing, but this suggestion is contradicted by the low magmatic water content that is generally inferred from chemical analyses of igneous martian meteorites. Here, however, we report the distributions of trace elements within pyroxenes of the Shergotty meteorite--a basalt body ejected 175 million years ago from Mars--as well as hydrous and anhydrous crystallization experiments that, together, imply that water contents of pre-eruptive magma on Mars could have been up to 1.8%. We found that in the Shergotty meteorite, the inner cores of pyroxene minerals (which formed at depth in the martian crust) are enriched in soluble trace elements when compared to the outer rims (which crystallized on or near to the martian surface). This implies that water was present in pyroxenes at depth but was largely lost as pyroxenes were carried to the surface during magma ascent. We conclude that ascending magmas possibly delivered significant quantities of water to the martian surface in recent times, reconciling geologic and petrologic constraints on the outgassing history of Mars.     

Global warming and climate forcing by recent albedo changes on Mars

For hundreds of years, scientists have tracked the changing appearance of Mars, first by hand drawings and later by photographs. Because of this historical record, many classical albedo patterns have long been known to shift in appearance over time. Decadal variations of the martian surface albedo are generally attributed to removal and deposition of small amounts of relatively bright dust on the surface. Large swaths of the surface (up to 56 million km2) have been observed to darken or brighten by 10 per cent or more. It is unknown, however, how these albedo changes affect wind circulation, dust transport and the feedback between these processes and the martian climate. Here we present predictions from a Mars general circulation model, indicating that the observed interannual albedo alterations strongly influence the martian environment. Results indicate enhanced wind stress in recently darkened areas and decreased wind stress in brightened areas, producing a positive feedback system in which the albedo changes strengthen the winds that generate the changes. The simulations also predict a net annual global warming of surface air temperatures by approximately 0.65 K, enhancing dust lifting by increasing the likelihood of dust devil generation. The increase in global dust lifting by both wind stress and dust devils may affect the mechanisms that trigger large dust storm initiation, a poorly understood phenomenon, unique to Mars. In addition, predicted increases in summertime air temperatures at high southern latitudes would contribute to the rapid and steady scarp retreat that has been observed in the south polar residual ice for the past four Mars years. Our results suggest that documented albedo changes affect recent climate change and large-scale weather patterns on Mars, and thus albedo variations are a necessary component of future atmospheric and climate studies.     

MD膜驱剂与季铵盐对油藏矿物润湿性的影响

用Washburn法对比了单分子双季铵盐MD膜驱剂、四乙基溴化铵和十六烷基三甲基溴化铵(CTAB)对油藏矿物润湿性的影响。研究结果表明,油藏矿物吸附MD膜驱剂或(Et)4NB亲水性大于CTAB,大庆、中原油砂吸附MD膜驱剂或(Et)4NB亲水性增加;油藏矿物吸附不同季铵盐亲油性大部分降低。沥青质油藏矿物(除沥青质-高岭土)吸附不同季铵盐亲油性都有增加; 油砂及沥青质油砂吸附MD膜驱剂亲油性小于(Et)4NB和CTAB,对油田的水驱和三次采油具有重要意义。     

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.     

Raman and FTIR spectroscopy of natural oxalates： Implications for the evidence of life on Mars

Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formarion of oxalates. Oxalates are most readily detected using Raman spectroscopy. A comparative study of a suite of natural oxalates including weddellite, whewellite, moolooite,humboldtine, glushinskite, natroxalate and oxammite has been undertaken using Raman spectroscopy. The minerals are characterised by the Raman position of the CO stretching vibration which is cation sensitive. The band is observed at 1468 cm^-1 for weddellite, 1489 cm^-1 for moolooite, 1471cm^-1 for glushinskite and 1456 cm^-1 for natroxalate. Except for oxammite, the infrared and Raman spectra are mutually exclusive indicating the minerals are bidentate. Differences are also observed in the water OH stretching bands of the minerals. The significance of this work rests with the ability of Raman spectroscopy to identify oxalates which often occur as a film on a host rock. As such Raman spectroscopy has the potential to identify the existence or pre-existence of life forms on planets such as Mars.     

烃源岩中黏土与可溶有机质相互作用研究展望

黏土吸附可溶有机质在沉积物和烃源岩中普遍存在,它将在烃源岩的研究中扮演重要的角色.烃源岩中可溶有机质与不可溶有机质都与黏土共存,但黏土吸附的可溶有机质在烃源岩中占有较大的比重,其形成贯穿于有机质的聚集、沉积、保存和成岩的全过程,可能是烃源岩中油气生成的一种天然母质.可溶有机质赋存于黏土矿物微孔隙、表面和层问,以多种键合方式结合形成了有机黏土复合体,具有自己独特的性质,这与烃源岩中的不可溶有机质--干酪根的特征完全不同.采用不同有机溶剂抽提得到的可溶有机质的量存在差异;不同类型的黏土矿物吸附有机质方式和数量也存在差异,展现了烃源岩中可溶有机质-黏土的关系极其复杂.因此,从黏土一可溶有机质的相互作用角度开拓烃源岩研究的思路,对有机质生烃机理的研究以及油气资源量的计算都具有重要的意义.     

An integrated view of the chemistry and mineralogy of martian soils

The mineralogical and elemental compositions of the martian soil are indicators of chemical and physical weathering processes. Using data from the Mars Exploration Rovers, we show that bright dust deposits on opposite sides of the planet are part of a global unit and not dominated by the composition of local rocks. Dark soil deposits at both sites have similar basaltic mineralogies, and could reflect either a global component or the general similarity in the compositions of the rocks from which they were derived. Increased levels of bromine are consistent with mobilization of soluble salts by thin films of liquid water, but the presence of olivine in analysed soil samples indicates that the extent of aqueous alteration of soils has been limited. Nickel abundances are enhanced at the immediate surface and indicate that the upper few millimetres of soil could contain up to one per cent meteoritic material.     

Recent and episodic volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera

The large-area coverage at a resolution of 10-20 metres per pixel in colour and three dimensions with the High Resolution Stereo Camera Experiment on the European Space Agency Mars Express Mission has made it possible to study the time-stratigraphic relationships of volcanic and glacial structures in unprecedented detail and give insight into the geological evolution of Mars. Here we show that calderas on five major volcanoes on Mars have undergone repeated activation and resurfacing during the last 20 per cent of martian history, with phases of activity as young as two million years, suggesting that the volcanoes are potentially still active today. Glacial deposits at the base of the Olympus Mons escarpment show evidence for repeated phases of activity as recently as about four million years ago. Morphological evidence is found that snow and ice deposition on the Olympus construct at elevations of more than 7,000 metres led to episodes of glacial activity at this height. Even now, water ice protected by an insulating layer of dust may be present at high altitudes on Olympus Mons.     

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.     

膨润土矿物固体电解质的制备及导电性能研究

以膨润土为原料,经硫酸处理后得到层状结构明显的矿物材料,通过制浆干燥的方法向层间有效插入Na+,制备了在室温下具有较高离子电导率的固体电解质.考察了矿物材料的微观结构、Na+含量及含水量对矿物材料电导率的影响,并用扫描电镜、能谱、红外光谱和X射线衍射对其结构进行了表征,结果表明,此法制备的膨润土矿物电解质材料在常温下离子电导率最高可达到7.81×10-4 S·cm-1,比传统的高温固相法提高了2倍.     

Possible seismic reflector in the lower crust： Evidence from fabrics and experiments of seismic velocity on layered gabbro at high temperature and high pressure

Lattice preferred orientations (LPO) of plagioclase and augite are measured on layered gabbro from the Panxi region, Sichuan Province. The LPO concentration [010] of plagioclase and [100] of augite are perpendicular to the foliation, which indicates a kind of growth fabric associated with crystallizing habits of minerals when the magma is solidifying under the compaction. Calculated seismic velocities based on LPO data of minerals give rise to rather strong anisotropy 5.81% and 5.54% for compressional seismic wave (Vp) and shear seismic wave (Vs), respectively. The experiments at high temperature and high pressure show that the P-wave velocity of layered gabbro is 6.4-6.97 km/s with the maximum Vp anisotropy 5.22% and the Poisson‘s ratio is between 0.28-0.31. According to the comparison of fabrics with seismic velocities of layered gabbro, it is suggested that the large-scale layered intrusive body or the similar layered geological body may exist in the lower crust of this area. Such a layered intrusive body which has strong seismic anisotropy may be the seismic reflector in the lower crust.     

基于主成分分析法的黄土灌溉区水-岩（土）相互作用研究

文章以甘肃省永靖县黑方台地区为对象,该地区是受长期灌溉水下渗导致地下水位抬升,进而诱发了大量黄土滑坡。为了进一步研究黑方台地下水的水-岩（土）相互作用对岩土体的影响,本文借助主成分分析法,对黑方台的地下水化学特征进行分析,并结合滑坡岩土体的易溶盐成分和矿物组成等特征做综合研究。采集滑坡体出水口处的地下水样测试水化学组成,选择前2个变量因子Z1、Z2作为主成分（分别占总方差的68.166%和20.576%）,分析地下水的水化学特征,便可反映90%左右的信息。主因子Z1主要反应易溶盐含量和水敏性矿物（长石类、方解石等）的水解作用对地下水化学成分的控制作用,主因子Z2反映微溶盐石膏（硫酸钙）矿物的溶解度随地下水离子浓度增加而增大和CaCO3的溶解、沉淀过程。研究表明,水-岩（土）相互作用会导致岩土体胶结性变差,微结构破坏,进一步累积会使岩土体产生大量裂隙和孔洞,最终将影响岩土体稳定性;另外,黄土中CaCO3的淋溶和迁移证明CaCO3淀积层顶部应为地下水入渗方式转变的分界线。地下水主成分分析的结果能反映出黑方台滑坡地下水与岩土体的相互作用的主要过程。     

Recent ice-rich deposits formed at high latitudes on Mars by sublimation of unstable equatorial ice during low obliquity

Observations from the gamma-ray spectrometer instrument suite on the Mars Odyssey spacecraft have been interpreted as indicating the presence of vast reservoirs of near-surface ice in high latitudes of both martian hemispheres. Ice concentrations are estimated to range from 70 per cent at 60 degrees latitude to 100 per cent near the poles, possibly overlain by a few centimetres of ice-free material in most places. This result is supported by morphological evidence of metres-thick layered deposits that are rich in water-ice and periglacial-like features found only at high latitudes. Diffusive exchange of water between the pore space of the regolith and the atmosphere has been proposed to explain this distribution, but such a degree of concentration is difficult to accommodate with such processes. Alternatively, there are suggestions that ice-rich deposits form by transport of ice from polar reservoirs and direct redeposition in high latitudes during periods of higher obliquity, but these results have been difficult to reproduce with other models. Here we propose instead that, during periods of low obliquity (less than 25 degrees), high-latitude ice deposits form in both hemispheres by direct deposition of ice, as a result of sublimation from an equatorial ice reservoir that formed earlier, during a prolonged high-obliquity excursion. Using the ice accumulation rates estimated from global climate model simulations we show that, over the past ten million years, large variations of Mars' obliquity have allowed the formation of such metres-thick, sedimentary layered deposits in high latitude and polar regions.     

川东北寒武纪盐盆成盐环境及其找钾意义

 四川盆地东北部寒武系蒸发盐发育,该区钻孔见有高矿化度卤水,建南地区中寒武统覃家庙组沉积厚层石膏及石盐(建深1 井),钻遇石盐累计厚度达120 m,各盐层之间仅夹有薄层石膏,石盐单层最厚达80 m(可能存在挤压增厚),结束了对于本区未达到石盐沉积的认识.对建深1 井岩盐沉积段岩屑样品(石盐岩屑尚难识别其是原生石盐还是次生石盐)的溴氯系数进行分析得出,其溴氯系数值相对较低,一般为0.05~0.22.将水溶与酸溶的钾离子百分含量进行对比,酸溶的钾离子含量明显高于水溶钾离子含量,约为水溶的1.3~2.0 倍,可能与石盐岩屑中存在较难溶于水的含钾矿物有关.川东北现有多口井钻遇寒武系高矿化度含(富)钾、溴、锂卤水,其含量最高可分别达4.6 g/L、886 mg/L 和148 mg/L,可进行综合利用.研究认为该区卤水的较高,Li⁺含量既不是完全由海水浓缩而成的沉积卤水,更不是溶滤盐类的结果,推测与该地区的水-岩作用、火山活动与深部来源的热水有关.综合分析本区的成钾条件和亚洲寒武系成盐成钾的广泛性,认为应关注及加强研究该区成盐找钾.     

Geology and insolation-driven climatic history of Amazonian north polar materials on Mars

Mariner 9 and Viking spacecraft images revealed that the polar regions of Mars, like those of Earth, record the planet's climate history. However, fundamental uncertainties regarding the materials, features, ages and processes constituting the geologic record remained. Recently acquired Mars Orbiter Laser Altimeter data and Mars Orbiter Camera high-resolution images from the Mars Global Surveyor spacecraft and moderately high-resolution Thermal Emission Imaging System visible images from the Mars Odyssey spacecraft permit more comprehensive geologic and climatic analyses. Here I map and show the history of geologic materials and features in the north polar region that span the Amazonian period (approximately 3.0 Gyr ago to present). Erosion and redeposition of putative circumpolar mud volcano deposits (formed by eruption of liquefied, fine-grained material) led to the formation of an Early Amazonian polar plateau consisting of dark layered materials. Crater ejecta superposed on pedestals indicate that a thin mantle was present during most of the Amazonian, suggesting generally higher obliquity and insolation conditions at the poles than at present. Brighter polar layered deposits rest unconformably on the dark layers and formed mainly during lower obliquity over the past 4-5 Myr (ref. 20). Finally, the uppermost layers post-date the latest downtrend in obliquity <20,000 years ago.     

分子沉积膜驱剂对油藏矿物润湿性的影响

分子沉积膜驱油 (简称MD膜驱油 )是一种新的提高原油采收率技术 .为考察MD膜驱剂吸附对不同性质的矿物表面润湿性的影响 ,利用Washburn法分别研究了水和正庚烷在这些矿物上的润湿性变化 .结果表明 ,具有强亲水活性中心的表面吸附MD膜驱剂后 ,亲水性会减弱 ;亲水性较弱的表面吸附MD膜驱剂后 ,水润湿性变化不大 ;中间润湿性的表面吸附MD膜驱剂后 ,水润湿性增强 .MD膜驱剂处理前后不同矿物表面亲水性和亲油性的变化幅度不尽一致 ,说明研究油藏矿物表面MD膜润湿性时需同时考察亲水性和亲油性 .