Results 201 to 210 of about 136,179 (257)
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Science, 1995
The Archean crust contains direct geochemical information of the Earth's early planetary differentiation. A major outstanding question in the Earth sciences is whether the volume of continental crust today represents nearly all that formed over Earth's history or whether its rates of creation and destruction have been approximately balanced since the ...
S A, Bowring, T, Housh
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The Archean crust contains direct geochemical information of the Earth's early planetary differentiation. A major outstanding question in the Earth sciences is whether the volume of continental crust today represents nearly all that formed over Earth's history or whether its rates of creation and destruction have been approximately balanced since the ...
S A, Bowring, T, Housh
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2012
In this chapter we will look at the environment of the early Earth as a habitat for life and at the primitive life forms that inhabited it. The early Earth was a very different planet from today's Earth. Hotter, much more volcanically active, with an oxygen-poor atmosphere and ocean waters that were probably slightly more acidic and more salty than ...
Westall, F., Selsis, Franck
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In this chapter we will look at the environment of the early Earth as a habitat for life and at the primitive life forms that inhabited it. The early Earth was a very different planet from today's Earth. Hotter, much more volcanically active, with an oxygen-poor atmosphere and ocean waters that were probably slightly more acidic and more salty than ...
Westall, F., Selsis, Franck
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Science, 1993
Ideas about atmospheric composition and climate on the early Earth have evolved considerably over the last 30 years, but many uncertainties still remain. It is generally agreed that the atmosphere contained little or no free oxygen initially and that oxygen concentrations increased markedly near 2.0 billion years ago, but the precise timing of and ...
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Ideas about atmospheric composition and climate on the early Earth have evolved considerably over the last 30 years, but many uncertainties still remain. It is generally agreed that the atmosphere contained little or no free oxygen initially and that oxygen concentrations increased markedly near 2.0 billion years ago, but the precise timing of and ...
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Astrobiology, 2003
A major goal of NASA's Origins Program is to find habitable planets around other stars and determine which might harbor life. Determining whether or not an extrasolar planet harbors life requires an understanding of what spectral features (i.e., biosignatures) might result from life's presence.
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A major goal of NASA's Origins Program is to find habitable planets around other stars and determine which might harbor life. Determining whether or not an extrasolar planet harbors life requires an understanding of what spectral features (i.e., biosignatures) might result from life's presence.
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Flash Heating on the Early Earth
Origins of life and evolution of the biosphere, 1999It has been suggested that very large impact events (approximately 500 km diameter impactors) sterilized the surface of the young Earth by producing enough rock vapor to boil the oceans. Here, we consider surface heating due to smaller impactors, and demonstrate that surface temperatures conductive to organic synthesis resulted. In particular, we focus
J R, Lyons, A R, Vasavada
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2007
The Earth is so far the only place in the Universe where life is known to exist. Is the Earth special, or are there other places both in our own solar system and beyond where life may have originated and either became extinct or still exists today? Hopefully, in the not to distant future we may find out.
Oliver Botta, Jeffrey L. Bada
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The Earth is so far the only place in the Universe where life is known to exist. Is the Earth special, or are there other places both in our own solar system and beyond where life may have originated and either became extinct or still exists today? Hopefully, in the not to distant future we may find out.
Oliver Botta, Jeffrey L. Bada
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Early differentiation of the Earth and the Moon
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2008We examine the implications of new182W and142Nd data for Mars and the Moon for the early evolution of the Earth. The similarity of182W in the terrestrial and lunar mantles and their apparently differing Hf/W ratios indicate that the Moon-forming giant impact most probably took place more than 60 Ma after the formation of calcium-aluminium-rich ...
Bourdon, Bernard +3 more
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Nature Geoscience, 2013
Some mantle plumes are enriched in 3He, but the source of this primordial isotope is unclear. The partitioning behaviour of helium between silicate and iron melts—as determined by experiments—suggests that sufficient helium may have been incorporated into the core when the Earth differentiated to explain the anomalous leakage at the Earth’s surface.
Bouhifd, Mohamed Ali +3 more
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Some mantle plumes are enriched in 3He, but the source of this primordial isotope is unclear. The partitioning behaviour of helium between silicate and iron melts—as determined by experiments—suggests that sufficient helium may have been incorporated into the core when the Earth differentiated to explain the anomalous leakage at the Earth’s surface.
Bouhifd, Mohamed Ali +3 more
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Impact Processes on the Early Earth
Elements, 2006At the beginning of the solar system, impacts and collisions were dominant processes. After an early collision that may have led to the formation of the Moon, both Earth and Moon suffered intense post-accretionary bombardment between about 4.5 and 3.9 billion years before present.
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2015
Contributors Preface Acknowledgements 1. Timing of nebula processes which shaped the precursors of the terrestrial planets Marc Chaussidon and Ming-Chang Liu 2. The Earth s building blocks Frederic Moynier and Bruce Fegley, Jr. 3. Earth and Terrestrial Planet Formation Seth A. Jacobson, Kevin J. Walsh 4.
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Contributors Preface Acknowledgements 1. Timing of nebula processes which shaped the precursors of the terrestrial planets Marc Chaussidon and Ming-Chang Liu 2. The Earth s building blocks Frederic Moynier and Bruce Fegley, Jr. 3. Earth and Terrestrial Planet Formation Seth A. Jacobson, Kevin J. Walsh 4.
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