Masters of disguise: can achondrite parent bodies hide beneath a chondritic cover?

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Chondrite meteorites are the most primitive known building blocks of terrestrial planetsas they show elemental abundances as still found in our Sun [1]. Other groups of meteorites knownas achondrites and iron meteorites show various degrees of differentiation resembling the Earth'sbasaltic crust and iron core, respectively. Traditionally, these categories of meteorites have beeninterpreted to derive from more primitive (chondrites) and more differentiated (achondrites, and irons)parent bodies, respectively. However, an alternative interpretation has it that even differentiatedparent bodies can retain an undifferentiated chondritic crust [2]. This theory is consistent withobservation of asteroid 21 Lutetia that has a chondritic surface composition but appears to beinternally differentiated [3]. That scenario could arise in small planetesimals that experience internalheating from short-lived radionuclide decay. Partial melting and internal magmatism would facilitatedifferentiation of the interior while an outer crust remains intact and unprocessed. However, thatregime will likely be restricted to a certain size and formation age of parent bodies. In earlier or largerplanetesimals, more intense heating and internal dynamics might lead to tectonic disruption and/orvolcanic resurfacing of the chondritic lid. A new generation of multi-phase reaction-transport modelsfor magma transport through deforming ductile-brittle rock [4-6] will allow us to put the hypotheticalstability of a chondritic crust on an achondrite parent body to the test!