Fragmentation of the High-mass "Starless'' Core G10.21-0.31: a Coherent Evolutionary Picture for Star Formation

G10.21-0.31 is a 70 $\mu$m-dark high-mass starless core ($M>300$ ${\mathrm{M}}_{\odot }$ within $r<0.15$ pc) identified in $Spitzer$, $Herschel$, and APEX continuum surveys, and is believed to harbor the initial stages of high-mass star formation. We present ALMA and SMA observations to resolve the internal structure of this promising high-mass starless core. Sensitive high-resolution ALMA 1.3 mm dust continuum emission reveals three cores of mass ranging 11-18 ${\mathrm{M}}_{\odot }$, characterized by a turbulent fragmentation. Core 1, 2, and 3 represent a coherent evolution at three different evolutionary stages, characterized by outflows (CO, SiO), gas temperature (${\mathrm{H}}_2\mathrm{C}\mathrm{O}$), and deuteration (${\mathrm{N}}_2{\mathrm{D}}^{+}\mathrm{/}{\mathrm{N}}_2{\mathrm{H}}^{+}$). We confirm the potential to form high-mass stars in G10.21 and explore the evolution path of high-mass star formation. Yet, no high-mass prestellar core is present in G10.21. This suggests a dynamical star formation where cores grow in mass over time.