Could some meteoritic stardust have originated from the winds of post-AGB stars and planetary nebula nuclei?

After very dense and slow winds erode the outer layer of an asymptotic giant branch (AGB) star down to a thin H-rich layer (~=10^-3 M_⊙) the star becomes a post-AGB star and evolves at constant luminosity towards hotter temperatures. It may then becomes a planetary nebula nucleus (PNN) at the centre of a planetary nebula (PN). During these phases, the thin H-rich surface layer of the star is eroded by winds. Stardust oxide and silicate grains are recovered from meteorites. The origin of the ``Group II grains'' that show enrichments in ¹⁷O and depletions in ¹⁸O is currently explained by invoking the occurrence of some kind of extra-mixing process in AGB stars. We suggest instead that these grains originated from the winds of post-AGB stars and PNN. These winds show the signature of H-burning. We will do this by comparing our predictions from stellar models to the compositions observed in Group II stardust oxide and silicate grains. We find that the composition of the thin H-rich layer lost in the post-AGB and PNN winds is close to that of Group II grains, however the match with the Al ratios needs to be improved. Considering the uncertainities in the ²⁵Mg and ²⁶Al proton capture rates may be helped in this respect.