53 research outputs found

    On the origin and evolution of the asteroid Ryugu: A comprehensive geochemical perspective

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    Presented here are the observations and interpretations from a comprehensive analysis of 16 representative particles returned from the C-type asteroid Ryugu by the Hayabusa2 mission. On average Ryugu particles consist of 50% phyllosilicate matrix, 41% porosity and 9% minor phases, including organic matter. The abundances of 70 elements from the particles are in close agreement with those of CI chondrites. Bulk Ryugu particles show higher δ18O, Δ17O, and ε54Cr values than CI chondrites. As such, Ryugu sampled the most primitive and least-thermally processed protosolar nebula reservoirs. Such a finding is consistent with multi-scale H-C-N isotopic compositions that are compatible with an origin for Ryugu organic matter within both the protosolar nebula and the interstellar medium. The analytical data obtained here, suggests that complex soluble organic matter formed during aqueous alteration on the Ryugu progenitor planetesimal (several 10’s of km), <2.6 Myr after CAI formation. Subsequently, the Ryugu progenitor planetesimal was fragmented and evolved into the current asteroid Ryugu through sublimation

    A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu

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    Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through a collective process called space weathering. The return of samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory study of space-weathering signatures on the most abundant type of inner solar system body: a C-type asteroid, composed of materials largely unchanged since the formation of the Solar System. Weathered Ryugu grains show areas of surface amorphization and partial melting of phyllosilicates, in which reduction from Fe3+ to Fe2+ and dehydration developed. Space weathering probably contributed to dehydration by dehydroxylation of Ryugu surface phyllosilicates that had already lost interlayer water molecules and to weakening of the 2.7 µm hydroxyl (–OH) band in reflectance spectra. For C-type asteroids in general, this indicates that a weak 2.7 µm band can signify space-weathering-induced surface dehydration, rather than bulk volatile loss

    A Private Cloud Environment for Teaching Search Engine Construction

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    Kyushu University installed a private cloud system, named “campus cloud system”, using VCL and CloudStack. For a graduate school exercise course on web search engine, the authors prepared a virtual machine on VCL, which had apache web server and GETA indexer preinstalled. This paper introduces an outline of the cloud system, the exercise, and also reports advantages and disadvantages of cloud based education

    Generation of Query URL for Search Sites

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    There are increasing number of sites that proved search facility of their own. They are a kind of databases open to public with HTML interface, and are referred as Invisible Web. We are developing a system, which integrates these specialized search sites for user’s purpose. A solution is the automatic wrapper generation. In this paper, we show how we can extract the attributes of the query parameters to construct a query URL for each site

    Automatic Estimation of Query Syntax for Search Sites

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    Pan-Yellow-Sea : International Workshop on Information Technologies for Network Era, March 7-8, 2002, Saga, JapanGeneral search engines like Yahoo! and Google are indispensable to cope with the flood of information on the Internet. But the quality of search results is not always good enough due to the vast size of the search space that these engines cover. On the other hand, many databases are becoming searchable on the Web, and many companies and organizations are providing their own search facility on the Web. We call such a site a search site. We are developing a system that integrates such search sites. To integrate these search sites we need to conceal the difference of the query syntax from the user. But the query syntax of these search sites vary. In this paper we propose a method that automatically determines the query syntax
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