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(abreviated) We aim to study the inner-wind structure (R<250 Rstar) of thewell-known red supergiant VY CMa. We analyse high spatial resolution(~0".24x0".13) ALMA Science Verification (SV) data in band 7 in which fourthermal emission lines of gaseous sodium chloride (NaCl) are present at highsignal-to-noise ratio. For the first time, the NaCl emission in the inner windregion of VY CMa is spatially resolved. The ALMA observations reveal thecontribution of up to four different spatial regions. The NaCl emission patternis different compared to the dust continuum and TiO2 emission already analysedfrom the ALMA SV data. The emission can be reconciled with an axisymmetricgeometry, where the lower density polar/rotation axis has a position angle of~50 degrees measured from north to east. However, this picture can not capturethe full morphological diversity, and discrete mass ejection events need to beinvoked to explain localized higher-density regions. The velocity traced by thegaseous NaCl line profiles is significantly lower than the average windterminal velocity, and much slower than some of the fastest mass ejections,signalling a wide range of characteristic speeds for the mass loss. GaseousNaCl is detected far beyond the main dust condensation region. Realising therefractory nature of this metal halide, this hints at a chemical processpreventing all NaCl from condensing onto dust grains. We show that in the caseof the ratio of the surface binding temperature to the grain temperature being~50, only some 10% of NaCl remains in gaseous form, while for lower values ofthis ratio thermal desorption efficiently evaporates NaCl. Photodesorption bystellar photons seems not to be a viable explanation for the detection ofgaseous NaCl at 220 Rstar from the central star, and instead, we proposeshock-induced sputtering driven by localized mass ejection events asalternative.

ALMA-resolved salt emission traces the chemical footprint and inner wind morphology of VY CMa