Asteroid 21 Lutetia , visited by the Rosetta spacecraft , plays a crucial role in the reconstruction of primordial phases of planetary objects .
Its high bulk density and its primitive chondritic crust ( 31 ) suggest that Lutetia could be partially differentiated .

We developed a numerical code , also used for studying the geophysical history of Vesta ( 9 ) , to explore several scenarios of internal evolution of Lutetia , differing in the strength of radiogenic sources and in the global post-sintering porosity .

The only significant heat source for partial differentiation is represented by ^ { 26 } Al , the other possible sources ( ^ { 60 } Fe , accretion and differentiation ) being negligible .

In scenarios in which Lutetia completed its accretion in less than 0.7 Ma from injection of ^ { 26 } Al in Solar Nebula and for post-sintering values of macroporosity not exceeding 30 vol . \% , the asteroid experienced only partial differentiation .

The formation of the proto-core , a structure enriched in metals and also containing pristine silicates , requires from 1 to 4 Ma : the size of the proto-core varies from 6 to 30 km .