EVOLVED STARS AND CIRCUMSTELLAR SHELLS

1. Measure the molecular abundances and probe the energetics of the outflows from thousands of evolved stars.

2. Image (at 0."1 resolution) hundreds of circumstellar shells.

3. Determine the rates and composition of mass-return to the ISM from hot stars, red giants, and supernovae.

4. Provide C/O ratios and isotope gradients in circumstellar shells -- tracers of the efficacy of C-N-O cycling and carbon dredge-up during He burning.

5. Provide sub-arcsecond imaging of all stellar dust shells detectable by SIRTF.

6. Measure the crucial 12C/13C ratio in the earliest phases of supernova development.