The top lower mantle is enriched in bridgmanite in the early Earth Global Earth seismology and geochemical deep magma ocean which was subject to highly turbulent analyses of volcanic products suggest that convection associated with a large heat flow at the Earth’s surface. The solidification of the magma-ocean took from the deep Earth's mantle is heterogeneous. 10 to 50 thousand years [2]. These events set the primordial However, the largest mantle heterogeneities thermochemical state of the mantle. Whether the primordial were likely produced in the Earth's early mantle was chemical-layered or homogeneous depends on the mechanism of magma-ocan solidification, with two end-member history by chemical segregation during the states being fractional or at equilibrium. Equilibrium solidification magma-ocean solidification. Based on the occurs when the crystallites remain suspended in the magma viscosity measurements of various silicate ocean (MO) during its convection, which results in a homogeneous primordial mantle. Alternatively, efficient sedimentation of the melts up to 30 GPa and /home/webapps/asp_fr/data/asp/publications/synchrotron-soleil/synchrotron-soleil-2020/soleil-highlights-2020-hd-ss-tc3250 K performed crystals yields a chemically-layered primordial mantle. The conjointly at the SOLEIL and SPring8 equations of the magma-ocean dynamics show that one of synchrotron facilities, the authors of this the major parameters defining which regime is established is the viscosity of the melt. It affects both the vigor of the MO study show that chemical segregation could convection and the speed of crystals settling, especially on the occur at mantle depths around 1000 km, later [3]. For this reason, it was formally needed to refine the which led to the formation of a (Mg,Fe)SiO vertical distribution of the magma-ocean viscosity, which was 3 not available until this work for the deep mantle. bridgmanite-enriched layer. A part of this layer could have resisted until today to EXPERIMENTS mantle mixing by convection. In-situ falling sphere viscometry is the best method to directly measure viscosity under high-pressure conditions. In this In the early stages of the Earth’s formation, the mantle meltedmethod, the viscosity of the melt is evaluated from the vertical almost completely up to great depths due to the massive energyvelocity of a sphere that is monitored at high speed through released by a giant Moon-forming impact [1]. It induced a verysequential synchrotron X-ray radiographic images (Figure 1). FIGURE 1 72