When
3:30 p.m., May 1, 2012
Where
Kuiper Space Sciences 308
Dr. Conel Alexander
Carnegie Institution of Washington
Dr. Alexander's host is Professor Tom Zega
"The Comet-meteorite Connection, and the Sources of Volatiles in the Terrestrial Planet Region"
Determining the source(s) of H, C and N in the terrestrial planet region is important for understanding not only the origin of life on Earth, but also dynamical processes in the solar protoplanetary disk (nebula) and during planet formation. Primitive chondritic meteorites are asteroidal fragments that retain records of the first few million years of Solar System history. It is becoming increasingly apparent that chondrites and comets shared many similarities at the time of their formation---volatile-rich ices, organic matter and fine-grained silicates---suggesting that there may be a genetic relationship. Indeed, two dynamical models (Levison et al., 2009; Walsh et al., 2011) designed to explain the current architecture of the Solar System predict that objects that formed in the Oort and Jupiter-family comet formation regions would have been implanted primarily in the outer asteroid belt. These models suggest that the implanted outer Solar System objects are the C-complex asteroids, which are thought to be the sources of the carbonaceous chondrites, while asteroids that formed in the inner Solar System belong to the S-complex that are the sources of the ordinary, Rumaruti and enstatite chondrites. At present, the only way to test these models is through the comparison of H isotopes in cometary and chondritic water. The H isotopic compositions of water in carbonaceous chondrites indicate that they did not form in the source regions of the measured comets. Nor is there H isotopic evidence for the massive influx of water ice from the outer Solar System invoked to explain the O isotopic composition of the inner Solar System (Lyons and Young, 2005; Yurimoto and Kuramoto, 2004). Finally, bulk H and N isotopic compositions suggest that the principal source of the Earths' volatiles were probably CI chondrite-like objects, accompanied by some solar-composition material, rather than Jupiter-family comets (Hartogh et al., 2011).
Carnegie Institution of Washington
Dr. Alexander's host is Professor Tom Zega
"The Comet-meteorite Connection, and the Sources of Volatiles in the Terrestrial Planet Region"
Determining the source(s) of H, C and N in the terrestrial planet region is important for understanding not only the origin of life on Earth, but also dynamical processes in the solar protoplanetary disk (nebula) and during planet formation. Primitive chondritic meteorites are asteroidal fragments that retain records of the first few million years of Solar System history. It is becoming increasingly apparent that chondrites and comets shared many similarities at the time of their formation---volatile-rich ices, organic matter and fine-grained silicates---suggesting that there may be a genetic relationship. Indeed, two dynamical models (Levison et al., 2009; Walsh et al., 2011) designed to explain the current architecture of the Solar System predict that objects that formed in the Oort and Jupiter-family comet formation regions would have been implanted primarily in the outer asteroid belt. These models suggest that the implanted outer Solar System objects are the C-complex asteroids, which are thought to be the sources of the carbonaceous chondrites, while asteroids that formed in the inner Solar System belong to the S-complex that are the sources of the ordinary, Rumaruti and enstatite chondrites. At present, the only way to test these models is through the comparison of H isotopes in cometary and chondritic water. The H isotopic compositions of water in carbonaceous chondrites indicate that they did not form in the source regions of the measured comets. Nor is there H isotopic evidence for the massive influx of water ice from the outer Solar System invoked to explain the O isotopic composition of the inner Solar System (Lyons and Young, 2005; Yurimoto and Kuramoto, 2004). Finally, bulk H and N isotopic compositions suggest that the principal source of the Earths' volatiles were probably CI chondrite-like objects, accompanied by some solar-composition material, rather than Jupiter-family comets (Hartogh et al., 2011).
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