Earth and Mars cases showing different crystallization timescales as lines. Black lines are reference (average) cases with η = 10¹⁸, Fe# = 10 and 20, and core temperatures of 4400 and 2400 K (respectively for Earth and Mars). For the properties we explore and associated references, see text. (a) Maximum Fe# for a given crystallization timescale. (b) Resulting density difference of the buffered layer as a function of the crystallization timescale.