نتایج جستجو برای: earth atmosphere

تعداد نتایج: 143613  

Journal: :Journal of Research of the National Bureau of Standards, Section D: Radio Science 1964

2009
D. Porcelli

We have previously presented a model for the distribution and transport of rare gases within the Earth [1,2,3,4] which explains the available observational data for mantle He, Ne, Ar, and Xe isotope compositions and provides specific prdctions regarding the rare gas isotopic compositions of the lower mantle, interactions between rare gas reservoirs, and mantle rare gas concentrations. Here we d...

2008
George H. Shaw

The chemistry of Earth’s atmosphere during its first 2–2.5Ga bears on several branches of geoscience including the origin of prebiotic molecules and life itself, early surface processes, the ‘‘faint young sun’’ problem, carbon isotope systematics, and the transition to an oxidized surface. The geologic record, as sparse as it is for this era, presents several difficulties for attempts to model ...

Journal: :Astrobiology 2007
Jeremy Bailey

Current proposals for the characterization of extrasolar terrestrial planets rest primarily on the use of spectroscopic techniques. While spectroscopy is effective in detecting the gaseous components of a planet's atmosphere, it provides no way of detecting the presence of liquid water, the defining characteristic of a habitable planet. In this paper, I investigate the potential of an alternati...

2005
David C. Catling Mark W. Claire

The evolution of the Earth’s atmosphere is essentially the story of atmospheric oxygen. Virtually every realm of the Earth sciences–biology, geology, geochemistry, oceanography and atmospheric science–is needed to piece together an understanding of the history of oxygen. Over the past decade, new data from these fields has shown that there were two significant increases in atmospheric O2 levels...

2013
N Dauphas

Earth’s volatile elements (H, C, and N) are essential to maintaining habitable conditions for metazoans and simpler life forms. However, identifying the sources (comets, meteorites, and trapped nebular gas) that supplied volatiles to Earth is not straightforward because secondary processes such as mantle degassing, crustal recycling, and escape to space modified the composition of the atmospher...

1998
YOUXUE ZHANG

Patterson (1956) established that the age of Earth is close to that of meteorites. Over the last 20 years, workers argued for younger age for core differentiation based on Pb-Pb model ages and tungsten isotopic data and for gas retention based on I-Xe modeling. However, disagreement is abundant, and the young age of Earth has not been widely accepted. In this work, I examine all radiogenic nobl...

نمودار تعداد نتایج جستجو در هر سال

با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید