Volcanically emitted sodium chloride as a source for Io's neutral clouds and plasma torus

The atmosphere of Jupiter's satellite Io is extremely tenuous, time variable and spatially heterogeneous. Only a few molecules--SO2, SO and S2--have previously been identified as constituents of this atmosphere, and possible sources include frost sublimation, surface sputtering and active volcanism. Io has been known for almost 30 years to be surrounded by a cloud of Na, which requires an as yet unidentified atmospheric source of sodium. Sodium chloride has been recently proposed as an important atmospheric constituent, based on the detection of chlorine in Io's plasma torus and models of Io's volcanic gases. Here we report the detection of NaCl in Io's atmosphere; it constitutes only approximately 0.3% when averaged over the entire disk, but is probably restricted to smaller regions than SO2 because of its rapid photolysis and surface condensation. Although the inferred abundance of NaCl in volcanic gases is lower than predicted, those volcanic emissions provide an important source of Na and Cl in Io's neutral clouds and plasma torus.     

尤里·苏梅克(1928～1997)

尤里·苏梅克（EugeneMShoemaker）于1997年7月18日不幸去世，享年69岁。苏梅克一生致力于地球、月球、行星及其表面冲击坑（crate）的研究，是星体冲击坑科学理论的奠基人。他还与其妻子卡洛琳（Garolyn）合作，在近地小行星和彗星观测方面，做出了开创性的贡献。苏梅克留给我     

关于《天才的视野》一书的评介

平心而论，《天才的视野：科学艺术中的视觉形象与创造》更象本随想录。如果一定要找出个主题的话．可以说，它主要讨论了科学理论及其发现过程中视觉表征的作用。作者（ArthurI．Miller）用了整整480页的篇幅，用心良苦地想使读者能在物理学史的长河里观潮捡贝，在作者偏爱的1905～1927年这段物理学的“黄金时代”驻足观望。本书首先简短地回顾了伽里略、彭加勒、爱因斯坦和毕加索的个人经历，猛烈抨击了将科学看作是纯粹社会构造的后现代主义，并试图以皮亚杰的同化、协调等概念来解释科学的发展和进步。作者在书中探究了毕加京受彭加勒…     

行为科学和社会科学的未来

行为科学和社会科学的未来赵乐静编译一、很重要也很无奈毫无疑问，处理社会公共事务必然要涉及到对人类行为的理解。现在，行为科学、社会科学正积极探索诸如暴力、经济、人口及改善人类行为能力和提高人类认知水平等方面的问题。如当代行为科学对人脑、结构语言学、人的...     

A common inversion under selection in Europeans

A refined physical map of chromosome 17q21.31 uncovered a 900-kb inversion polymorphism. Chromosomes with the inverted segment in different orientations represent two distinct lineages, H1 and H2, that have diverged for as much as 3 million years and show no evidence of having recombined. The H2 lineage is rare in Africans, almost absent in East Asians but found at a frequency of 20% in Europeans, in whom the haplotype structure is indicative of a history of positive selection. Here we show that the H2 lineage is undergoing positive selection in the Icelandic population, such that carrier females have more children and have higher recombination rates than noncarriers.