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Meteoritic Constraints on Models of the Solar Nebula: The Abundances of Moderately Volatile ElementsThe "moderately volatile" elements are those which condense (or evaporate) in the temperature range 650 - 1350 K, as a mix of material with solar abundances is cooled (or heated) under equilibrium conditions. Their relative abundances in chondritic meteorites are solar (or "cosmic", as defined by tile composition of CI meteorites) to within a factor of several, but vary within that range in a way that correlates remarkably well with condensation temperature, independent of chemical affinity. It has been argued that this correlation reflects a systematically selective process which favored the accretion of refractory material over volatile material from a cooling nebula. Wasson and Chou suggested that condensation and settling of solids contemporaneously with the cooling and removal of nebular gas could produce tile observed abundance patterns, but a quantitative model has been lacking. We show that the abundance patterns of the moderately volatile elements in chondritic meteorites can be produced, in some degree of quantitative detail, by models of the solar nebula that are designed to conform to observations of T Tauri stars and the global conservation laws. For example, even if the local surface density of the nebula is not decreasing, condensation and accretion of solids from radially inflowing gas in a cooling nebula can result in depletions of volatiles, relative to refractories, like those observed. The details of the calculated abundance patterns depend on (but are not especially sensitive to) model parameters, and can exhibit the variations that distinguish the meteorite classes. Thus it appears that nebula characteristics Such as cooling rates, radial flow velocities, and particle accumulation rates can be quantitatively constrained by demanding that they conform to meteoritic data; and the models, in turn, can produce testable hypotheses regarding the time and location of the formation of the chondrite parent bodies and the planets.
Document ID
20020005095
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Cassen, P.
(NASA Ames Research Center Moffett Field, CA United States)
Cuzzi, Jeffrey N.
Date Acquired
August 20, 2013
Publication Date
January 1, 1994
Subject Category
Solar Physics
Meeting Information
Meeting: 26th Annual Meeting of the Division for Planetary Sciences
Location: Washington, DC
Country: United States
Start Date: October 29, 1994
End Date: November 9, 1994
Funding Number(s)
PROJECT: RTOP 452-21-93-99
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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