Lava worlds: From early earth to exoplanets     

《Chemie der Erde / Geochemistry》2021,81(2):125735

The magma ocean concept was first conceived to explain the geology of the Moon, but hemispherical or global oceans of silicate melt could be a widespread “lava world” phase of rocky planet accretion, and could persist on planets on short-period orbits around other stars. The formation and crystallization of magma oceans could be a defining stage in the assembly of a core, origin of a crust, initiation of tectonics, and formation of an atmosphere. The last decade has seen significant advances in our understanding of this phenomenon through analysis of terrestrial and extraterrestrial samples, planetary missions, and astronomical observations of exoplanets. This review describes the energetic basis of magma oceans and lava worlds and the lava lake analogs available for study on Earth and Io. It provides an overview of evidence for magma oceans throughout the Solar System and considers the factors that control the rocks these magma oceans leave behind. It describes research on theoretical and observed exoplanets that could host extant magma oceans and summarizes efforts to detect and characterize them. It reviews modeling of the evolution of magma oceans as a result of crystallization and evaporation, the interaction with the underlying solid mantle, and the effects of planetary rotation. The review also considers theoretical investigations on the formation of an atmosphere in concert with the magma ocean and in response to irradiation from the host star, and possible end-states. Finally, it describes needs and gaps in our knowledge and points to future opportunities with new planetary missions and space telescopes to identify and better characterize lava worlds around nearby stars.  相似文献   

Was FLK North levels 1–2 a classic “living floor” of Oldowan hominins or a taphonomically complex palimpsest dominated by large carnivore feeding behavior?     

H.T. Bunn  A.Z.P. Mabulla  M. Domínguez-Rodrigo  G.M. Ashley  R. Barba  F. Diez-Martín  K. Remer  J. Yravedra  E. Baquedano 《Quaternary Research》2010,74(3):355-362

From excavation at FLK North levels 1–2 in 1960–1962, Mary Leakey reported approximately 1200 Oldowan artifacts and 3300 large mammal fossils as a hominin “living floor”. Preliminary taphonomic analysis by Bunn seemed supportive, based on the presence of some cut-marked bones, the concentration of several dozen bovid individuals, and the relative abundance of limbs and mandibles over other axial elements. Recent taphonomic analysis of Leakey's entire fossil assemblage by Domínguez-Rodrigo and Barba, however, documents a minor hominin role at the site, contrasted to the dominant role of carnivores. Felids brought prey animals; hyenas scavenged from abandoned felid meals. At different times, hominins butchered several bovids and discarded artifacts at this dynamic location. Since 2006, renewed excavations at FLK North and other sites by the Olduvai Paleoanthropology and Paleoecology Project (TOPPP) have expanded artifact and fossil samples and implemented new analytical approaches to clarify taphonomic histories of the Olduvai paleolandscape. At FLK North, > 1000 new large mammal fossils from levels 1 to 2 show minimal butchery evidence amid abundant evidence of carnivore gnawing/fracture, rodent gnawing, and sediment abrasion. To help guide future excavation and analyses, we have developed several alternative working hypotheses of site formation.  相似文献   

台湾海峡中、北部浮游有孔虫同海流和沉积环境的关系   总被引：1，自引：0，他引：1  

方惠瑛 《海洋与湖沼》1995,26(5):42-551

于1987年7月和8月及1988年5月和7月，在台湾海峡中、北部海域，利用浮游生物网和蚌式采泥器分别采集了水层中的浮游有孔虫标本和表层沉积里的浮游有孔虫遗壳样品。对活体和遗壳在数量和组成方面对比分析研究表明，调查海区暖水性最强的水域位于东南角的A5站一带，海峡暖流水由此向北延伸，在海坛岛以东D1站附近，因与闽浙沿岸水交汇而减弱。遗壳高值区位于深水的盆地，活体则出现在台地上，两者分布不一致。其原因在于盆地受冲刷，沉积作用缓慢，遗壳被浓缩；台地沉积速率高，遗壳数量被稀释。  相似文献   

地磁倒转与生物灭绝因果关系研究五十年   总被引：1，自引：0，他引：1       下载免费PDF全文

魏勇  万卫星 《地球物理学报》2014,57(11):3841-3850

地磁场源于地球内部的地核发电机,经由近3000 km厚的地幔和地壳到达地面,穿过生物圈、大气层和电离层后延展至太空形成磁层.地磁场对生物圈有双重保护作用:阻挡了高能粒子向内入侵,也避免了氧和水等挥发性物质向外逃逸.尽管地磁场在几十亿年的时间里帮助维持了地球的宜居性,人们仍认为地磁倒转所导致的保护作用削弱会给生物圈带来深刻的负面影响,甚至是生物灭绝.本文梳理地磁倒转与生物灭绝因果关系研究的五十年发展历程,结合历史背景评介早期"一对一"假说的得与失,并着重阐述空间环境变化在最新提出的"多对一"假说中的重要作用.这些研究成果已经清晰地说明,从地核到磁层的地球各圈层是一个耦合的复杂系统,地球演化中的重大事件应当从地球系统科学的角度来看待,并借助比较行星学来研究和理解.  相似文献   

Forecast and optimal allocation of production,living and ecology water consumption in Zhangye,China     

《Physics and Chemistry of the Earth》2016

The water crisis is one of three crises that are persecuting the world. China is among the countries that face severe water shortages. Water scarcity and water pollution have seriously affected China's sustainable development in terms of the economy and society. Water resources per capita of China is only one quarter of the world's average. In addition, about 70 percent of China's rivers, lakes, and reservoirs are affected by pollution. Due to limited water resources, a crucial issue for the sustainable development of the watershed is how to resolve the human/nature competition for water and how to achieve the coordinated development of the economy, society and ecology. On the basis of defining water consumption for production, living and ecology (WPLE), this paper proposes a framework for forecasting and optimally allocating WPLE. Using Zhangye, in the middle reaches of the Heihe River Basin as the case study area, we forecasted and optimally allocated WPLE under three development scenarios, i.e. the conventional development scenario (CDS), the economy-priority development scenario (EPDS) and the environmentally sustainable development scenario (ESDS). In 2010, the proportions of WPLE in Zhangye were 87.73%, 2.74% and 9.53%, respectively. In 2020, the proportions of WPLE will be 74.80%, 4.50% and 20.70% under the CDS, 76.16%, 5.27% and 18.57% under the EPDS, and 74.99%, 4.51% and 20.50% under the ESDS. In the future, the proportion of production water consumption of Zhangye will drastically decrease, while the proportion of ecological water consumption will significantly increase. The main contradiction of the co-evolution of WPLE of Zhangye is the competitiveness of production and living water consumption with ecological water consumption.  相似文献   

The emerging politics of the Arctic Ocean. Future management of the living marine resources     

《Marine Policy》2015

This article seeks to identify and analyze the most important political issues at stake with respect to the ongoing process regarding the future management of living resources in the high seas of the Arctic Ocean. Through assessing the potential for future commercial utilization of marine resources in the Arctic Ocean and analyzing the differences between the interests of engaged stakeholders in the process, the article seeks to answer whose interests and norms seem to most strongly influence the unfolding political processes and preliminary outcomes. The article concludes by identifying how the five Arctic coastal states have retained the upper hand in this process through skilled political entrepreneurship, the devotion of necessary resources and the political commitment of their respective governments.  相似文献   

黄河流域山东段“三生空间”分类及其时空格局变化分析          下载免费PDF全文

寻妍  马绍伟  王哲  冯海燕  张金盈  王磊 《山东国土资源》2022,38(10)

本文以黄河流域（山东段）为研究区，构建了基于山东省地理省情监测数据的“三生空间”分类体系，运用格网化研究方法分析了2017年以来黄河流域（山东段）“三生空间”时空格局及其演变情况。研究成果表明黄河流域（山东段）“三生空间”以生产空间为主，其次为生态空间，面积最少的为生活空间。近年来，“三生空间”时空演变情况为生活空间、生态空间面积增加，生产空间面积下降。黄河流域（山东段）“三生空间”研究成果可为国土空间优化提供借鉴意义。  相似文献   

A new insight into changes in protoplanetary disk structure caused by change in stellar mass     

《New Astronomy》2022

  相似文献