Chondrites as samples of differentiated planetesimals

By L. Elkins‐Tanton, B. Weiss, Maria T. Zuber. 2009

265 citations recorded by the source corpus.

Abstract Chondritic meteorites are unmelted and variably metamorphosed aggregates of the earliest solids of the solar system. The variety of metamorphic textures in chondrites motivated the “onion shell” model in which chondrites originated at varying depths within a parent body heated primarily by the short-lived radioisotope 26 Al, with the highest metamorphic grade originating nearest the center. Allende and a few other chondrites possess a unidirectional magnetization that can be best explained by a core dynamo on their parent body, indicating internal melting and differentiation. Here we show that a parent body that accreted to >~200 km in radius by ~ 1.5 Ma after the formation of calcium–aluminum-rich inclusions (CAIs) would have a differentiated interior, and ongoing accretion would add a solid undifferentiated crust overlying a differentiated interior, consistent with formational and evolutionary constraints inferred for the CV parent body. This body could have produced a magnetic field lasting more than 10 Ma. This hypothesis represents a new model for the origin of some chondrites, presenting them as the unprocessed crusts of internally differentiated early planetesimals. Such bodies may exist in the asteroid belt today; the shapes and masses of the two largest asteroids, 1 Ceres and 2 Pallas, can be consistent with differentiated interiors, conceivably with small iron cores with hydrated silicate or ice–silicate mantles, covered with undifferentiated crusts.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/5a4cde4bd25a7b3d9d0775157203a3866d04ce62

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Citations in the corpus

Spectral reflectance properties of carbonaceous chondrites: 1. CI chondrites (2012, background): “CVs also provide insights into possible early Solar System heating events of planetesimals (e.g., Weiss et al., 2010; Elkins-Tanton et al., 2011; Humayun and Weiss, 2011).”
Melting and differentiation of early-formed asteroids: The perspective from high precision oxygen isotope studies (2017, background): “…it has been proposed that at least some of the carbonaceous chondrites present in our meteorite col- lections are essentially late accreting materials that formed the outer layers to internally differentiated, early-formed planetesimals (Elkins-Tanton et al., 2011; Weiss and Elkins-Tanton, 2013).”
The taxonomic distribution of asteroids from multi-filter all-sky photometric surveys (2013, background): “Nevertheless, recent models find that large bodies even though masked with fairly primitive surfaces could actually have differentiated interiors (Elkins-Tanton et al., 2011; Weiss et al., 2012).”
Magma oceans in the inner solar system (2012, background): “References for ages ( far left) of core formation in iron meteorites, formation of chondrules, and genesis of angrites and eucrites from Elkins-Tanton et al. (2011b) and this review.”
The Compositional Structure of the Asteroid Belt (2015, background): “pyroxene-rich crust, olivine-rich mantle, and iron core may be incorrect or uncommon (Elkins-Tanton et al., 2011). The differentiation models cause an asteroid’s interior to heat and melt due to the decay of (26)Al, but the exterior remains unheated and primitive (see chapter by Scheinberg et al.). ”
The Non-carbonaceous–Carbonaceous Meteorite Dichotomy (2020, background): “Alternatively, the secondary dust may also derive from the primitive, undifferentiated crust of larger planetesimals (Elkins-Tanton et al. 2011).”
Differentiated Planetesimals and the Parent Bodies of Chondrites (2013, background): “An unsintered crust of CV carbonaceous chondrite composition may have a density between ∼2,700 and 2,900 kg m−3, whereas the density of molten CV chondrite over a range of temperatures and pressures is between ∼2,900 and 3,000 kg m−3 (Elkins-Tanton et al. 2011).”
Towards initial mass functions for asteroids and Kuiper Belt Objects (2010, background): “This is not to say their interiors were never heated, or even partially melted (Elkins-Tanton and Weiss 2009) but there are only a few asteroid surfaces manifesting widespread and complete melting, as on Vesta.”
Density of asteroids (2012, background): “These observables however tell us about surface composition only, which may or may not be reflective of the bulk composition of the body (Elkins-Tanton et al., 2011).”
The Effect of Jupiter's Formation on the Distribution of Refractory Elements and Inclusions in Meteorites (2017, background): “Because the pressure maximum beyond Jupiter is a natural location for solids to accrete, our model supports (but does not require) the idea of a single parent body of the Eagle Station pallasites and CK and CV chondrite, as suggested by Elkins-Tanton et al. (2011), based on paleomagnetism studies.”