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We report on the abundance analysis of two red giants in the faint Herculesdwarf spheroidal (dSph) galaxy. These stars show a remarkable deficiency in theneutron-capture elements, while the hydrostatic alpha-elements (O, Mg) arestrongly enhanced. Our data indicate [Ba/Fe] and [Mg/Fe] abundance ratios of<-2 dex and ~+0.8 dex, respectively, with essentially no detection of othern-capture elements. In contrast to the only other dSph star with similarabundance patterns, Dra 119, which has a very low metallicity at [Fe/H]=-2.95dex, our objects, at [Fe/H]~-2.0 dex, are only moderately metal poor. Themeasured ratio of hydrostatic/explosive alpha-elements indicates that high-mass(~35 M_sun) Type II supernovae progenitors are the main, if not only,contributors to the enrichment of this galaxy. This suggests that starformation and chemical enrichment in the ultrafaint dSphs proceedsstochastically and inhomogeneously on small scales, or that the IMF wasstrongly skewed to high mass stars. The neutron capture deficiencies and the[Co/Fe] and [Cr/Fe] abundance ratios in our stars are similar to those in theextremely low metallicity Galactic halo. This suggests that either our starsare composed mainly of the ejecta from the first, massive, population III stars(but at moderately high [Fe/H]), or that SN ejecta in the Hercules galaxy werediluted with ~30 times less hydrogen than typical for extreme metal-poor stars.

The Highly Unusual Chemical Composition of the Hercules Dwarf Spheroidal Galaxy