火星探测:黄钾铁矾原地K-Ar定年

为了更好地确定火星不同地形所记录的气候变化的时间尺度,确定火星历史上重大事件的绝对年龄,并校准陨石坑率,需要从火星原地或从返回样品中获得精确的年龄数据.原地K-Ar定年是目前比样品返回更为实用的一种精确远程定年技术.黄钾铁矾(KFe₃(SO₄)₂(OH)₆),是火星上广泛存在的唯一一种通过就位探测、轨道遥感探测、陨石研究三种手段都确定存在的含钾硫酸盐矿物,它已被用于K-Ar和⁴⁰Ar/³⁹Ar精确定年.火星上黄钾铁矾的保存提供了火星上含水过程的性质和持续时间的信息,不同年龄的黄钾铁矾能有效地解读火星历史上地表水流动时期及过渡到当前干旱气候之间的演变历史.本文总结了近年来火星上黄钾铁矾存在的区域、矿物学特征、在火星上的稳定性、原地K-Ar定年的研究现状、黄钾铁矾氩扩散动力学等,探讨了黄钾铁矾原地K-Ar定年的关键科学问题、火星采样返回需求、未来研究方向等.     

Ten years of the Astrophysics Data System

Guenther Eichhorn celebrates a decade in which the Astrophysics Data System has gone from a NASA abstract service to an essential tool for astronomy researchers worldwide.     

Ten years of barium build-up in the Teign

New analyses of <250 μm sediments from the river Teign, Devon, UK show spectacular increases of barium. In the middle river section levels are 1.5–3.5 times those obtained during a 1976 study. Although no mining has taken place in the region since the Bridford Baryte Mine closed in 1958, the former orefield is scattered with mine dumps, and some of these have been reworked since 1982. Catchment streams draining this mineralized area continue to supply sediments enriched with heavy metals to the Teign river. A peak value there reaches 12% Ba, largely in the form of barytes (BaSO₄). By comparison, barium enrichment in the Teign estuary is modest. Small increases in the middle estuary may be significant, however, in a zone where both river- and marine-derived detritus is deposited.     

1980–1990: Ten years of geochemical investigation at Phlegrean Fields (Italy)

A systematic geochemical investigation on the thermal manifestations of the volcanic area of Phlegrean Fields started in 1980, with the aim of obtaining useful information about the changes possibly occurring at the same time of vertical ground movements, termed as “bradyseismic”, which frequently interested this area.The attention was initially given to the fumaroles and the boiling pools of Solfatara and Pisciarelli, then subsequently extended to thermal springs, dug wells, and crater lakes.Analytical data pertaining to a period preceding the last crisis of 1982–1984 were then available, as well as other data collected during the previous crisis of 1970; a comprehensive picture of the variations observed before, during and after the acceleration of vertical movement has been drawn.According to the results obtained, the intrusion of a magmatic body as the trigger of the observed ground deformation is considered unrealistic. The whole area appears now in a quiet stage, and no further perturbation is expected without previous significant tectonic activity; chemical precursors appear suitable for an early detection of changes occurring at depth, to forecast possible consequences to be expected in the surface environment.     

印度洋海啸预警系统10年发展概况

<正>2004年12月26日,印度洋海啸导致25万人丧生,500万人需要紧急援助,180万居民无家可归。这场自然灾害给广大地区带来了毁灭性灾难,以及随之而来的悲痛和焦虑,特别是对印尼、泰国和斯里兰卡的影响超出了想象,而这主要是由于当时缺少对整个印度洋地区的预警设备和灾难管理计划。灾难过后,德国和国际社会立即表示支持。在德国洪涝灾民援助框架下,德国联邦     

New views of the Earth's interior

The Earth beneath our feet is a complex place. James Wookey reports on a meeting that took a broad multidisciplinary approach to understanding its composition, structure and dynamics.     

Investigations on the runoff generation at the profile and plot scales,Swiss Emmental

This article describes an investigation on runoff generation at different scales in the forested catchment of the Sperbelgraben in the Emmental region (Swiss Prealps) where studies in the field of forest hydrology have a history of 100 years. It focuses on the analysis of soil profiles and the subsequent sprinkling experiments above them (1 m²), as well as on surface runoff measurements on larger plots (50 to 110 m²). In the Sperbelgraben investigation area, two very distinct runoff reactions could be observed. On the one hand, very high production of saturation overland flow was registered on wet areas of gleyic soils, with runoff coefficients between 0·39 and 0·94 for profile irrigation. On the other hand, almost no surface runoff was measured on Cambisols, with the exception at some sites of a hydrophobic reaction detected at the beginning of storms after dry periods (coefficients for profile irrigation: 0·01–0·16). This pattern was observed during 1 m² soil plot irrigation and on surface runoff plots. Apart from a less distinctive signal of the water‐repellent litter layer on the larger surface runoff plots, the dominant hydrological processes at the two scales are the same. The determined runoff reaction at the two scales corresponds well with information from a forest site type map describing soil and vegetation characteristics and used as a substitute for a soil map in this study. Theoretical considerations describing forest influence on flood discharge are discussed and evaluated to be in good agreement with observations. These findings are a sound foundation for application in hydrological catchment modelling. Copyright © 2006 John Wiley & Sons, Ltd.     

Geochemical modeling of evaporation processes on Mars: Insight from the sedimentary record at Meridiani Planum

New data returned from the Mars Exploration Rover (MER) mission have revealed abundant evaporites in the sedimentary record at Meridiani Planum. A working hypothesis for Meridiani evaporite formation involves the evaporation of fluids derived from the weathering of martian basalt and subsequent diagenesis. On Earth, evaporite formation in exclusively basaltic settings is rare. However, models of the evaporation of fluids derived from experimentally weathering synthetic martian basalt provide insight into possible formation mechanisms. The thermodynamic database assembled for this investigation includes both Fe²⁺ and Fe³⁺ in Pitzer's ion interaction equations to evaluate Fe redox disequilibrium at Meridiani Planum. Modeling results suggest that evaporation of acidic fluids derived from weathering olivine-bearing basalt should produce Mg, Ca, and Fe-sulfates such as jarosite and melanterite. Calculations that model diagenesis by fluid recharge predict the eventual breakdown of jarosite to goethite as well as the preservation of much of the initial soluble evaporite component at modeled porosity values appropriate for relevant depositional environments (< 0.30). While only one of several possible formation scenarios, this simple model is consistent with much of the chemical and mineralogical data obtained on Meridiani Planum outcrop.     

Hydrological flow paths at the allt A' mharcaidh catchment: An analysis of plot and catchment scale observations

An integrated programme of hydrological monitoring at the 10 km² Allt a' Mharcaidh catchment in north-east Scotland has been based on observations at plot, hillslope and catchment scale. The resonse of the principal soil types has been characterized from a combination of throughflow and three-dimensional tensiometer data at plot scale, and plot sequences have been used to investigate hillslope scale effects. Seep emergence is associated with downslope drainage and local topographic convergence; in parallel preferential pathways generate a highly dynamic throughflow response. Catchment and subcatchment hydrographs mirror the twin dynamic observed at hillslope scale, and a unified hypothesis of response is presented which is consistent with all scales of observations.     

Hazard assessment at volcanic fields: the Campi Flegrei case history

Volcanological analysis of the 10 000 yr –1538 explosive activity at Campi Flegrei shows that the most common explosive eruptions are characterized by the emplacement of flow or surge deposits, originating from the interaction between magma and shallow and/or sea water. The minimum volumes of pyroclastic products range between 0.04 and 0.7 km³; the proximal areas covered by these products range from 3–4 to 40–50 km². The pyroclastic flow and surge deposits occurring inside the caldera have been strongly controlled by pre-existent morphology; because of this, the area of present Napoli city was blanketed by approximately 5 m of pyroclastic deposits, during the last 5000 yr.Previous analysis suggests that the presence of even very low topographic obstacles may influence pyroclastic density current run out such that future eruptive deposits would mainly be confined inside the caldera rim. We suggest that a future eruption at Campi Flegrei would not seriously involve the urbanized area of Napoli city located on the hills. On the contrary, the plains located on the eastern side of the caldera (Fuorigrotta, Bagnoli) would be the most damaged area.