Asteroid thermal evolution

The chondrite parent bodies obviously could not have accreted before their constituent chondrules formed. Based on the formation times of chondrules, accretion of the ordinary chondrite parent bodies began 2.5-3 Myr after CAIs (4565.7—4565.2 Ma). The end of accretion can be inferred from the metamorphic history of the chondrite parent bodies. Isotopic data from metamorphic assemblages, coupled with thermal modeling of the chondrite parent bodies, suggest that the time of peak metamorphism for the H chondrite parent body was at-4563 Ma. As will be discussed in Chapter 11, it is likely that the source of heat for metamorphism on chondrite parent bodies was the decay of26 Al, perhaps with a contribution from 60Fe. Thermal evolution models indicate that accretion of chondritic asteroids could not have occurred earlier than -2 Myr after CAI formation, or they would have melted. 

After the cores of the differentiated asteroids had crystallized, a slow cooling period commenced. During this period the most prominent feature of iron meteorites evolved—the Widmanstatten pattern (Figure 8). Several characteristics of the Widmanstatten pattern may be used to constrain the thermal evolution and the sizes of the iron meteorite parent bodies. 

Meteorites provide perhaps the best record of the chemical evolution of small bodies in the Solar System, and this record is supplemented by asteroidal spectroscopy. Meteorites show progressive degrees of thermal processing on their parent asteroids, from primitive carbonaceous chondrites that contain percent-level quantities of water, through ordinary chondrites that show a wide range of degree of thermal metamorphism, to the achondrites that have been melted and differentiated. 

Bottke W. F., Vokrouhlicky D., Rubincam D., and Broz M. (2002) The effect of Yarkovsky thermal forces on the dynamical evolution of asteroids and meteoroids. In Asteroids III (eds. W. F. Bottke, A. Cellino, P. Paolicchi, and R. Binzel). University of Arizona Press, Tucson, pp. 395 -408. 

Hafiiium-tungsten chronometry, thermal modeling of asteroids, numerical simulations of planetary accretion, and experimental petrology combine to provide a consistent picture for the formation and early evolution of planetary bodies in the inner solar system. Thermal modeling indicates that heating by Al decay will cause planetesimals that accreted within the first -1 Myr of the solar... 

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