  Icy grain mantles are the main reservoir of the volatile elements that link
chemical processes in dark, interstellar clouds with the formation of planets
and composition of their atmospheres. The initial ice composition is set in the
cold, dense parts of molecular clouds, prior to the onset of star formation.
With the exquisite sensitivity of JWST, this critical stage of ice evolution is
now accessible for detailed study. Here we show the first results of the Early
Release Science program "Ice Age" that reveal the rich composition of these
dense cloud ices. Weak ices, including, $^{13}$CO$_2$, OCN$^-$, $^{13}$CO, OCS,
and COMs functional groups are now detected along two pre-stellar lines of
sight. The $^{12}$CO$_2$ ice profile indicates modest growth of the icy grains.
Column densities of the major and minor ice species indicate that ices
contribute between 2 and 19% of the bulk budgets of the key C, O, N, and S
elements. Our results suggest that the formation of simple and complex
molecules could begin early in a water-ice rich environment.
