Powering ganymede’s dynamo with protracted core formation

Ganymede is the only known moon with an active dynamo today. Previous studies interpret Ganymede’s dynamo as arising from convection in a metal core that formed billions of years ago. However, Ganymede likely accreted too cold to form with a metal core, which confounds interpretations of Ganymede’s magnetic field as a constraint on the moon’s broader history. Here we re-evaluate the thermal evolution of Ganymede’s rock-metal interior from a cold start. Our models show that Ganymede’s observed dynamo is consistent with ongoing core formation—a process not yet observed elsewhere. If Ganymede has an Fe-FeS core with a sub-eutectic composition, then gradual mantle warming may expel dense Fe melt onto the growing protocore and stir liquid metal, sustaining a dynamo for billions of years., , , # Powering Ganymede’s dynamo with protracted core formation Dataset DOI: [10.5061/dryad.1rn8pk17z](https://doi.org/10.5061/dryad.1rn8pk17z) ## Description of the data and file structure Our data is primarily code and model output of simulations for the thermal evolution of Ganymede. Some compiled data of Fe-FeS melting is also included. ### Files and variables * Code_and_data_files.zip The following tabulated (.csv) data files are listed below. The names and units of each column are listed in bold and in parentheses, respectively. **ps_spider_web.csv**: results of the parameter sensitivity (Figure 4a–f). * **Xm0** (wt.% Fe-FeS) - Initial mass fraction of metal in the rock-metal mixture. * **Xs0** (wt.% S) - Initial mass fraction of sulfur in the Fe-FeS alloys. * **Xw0** (wt.% H~2~O) - Initial mass fraction of water in the hydrated rock endmember. * **fK** ([^40^K]%) - Fraction of ^40^K leached throughout silicate dehydration. * **PT** (TW) - Total tidal dissipation in the silica...,