Janet Bowey (Cardiff)

Astronomical dust is a repository of information on the evolution of metallicity in galaxies and of stellar evolution because many of the chemical elements condense into dust grains once they escape stellar interiors.  Two types persist in most dusty galaxy environments: carbon-rich dust (e.g. PAHs, SiC, hydrogenated-amorphous carbon) and oxygen-rich dust (e.g. silicates and oxides). Both have infrared features which will be observed by spectrometers on JWST. If the range of materials known to meteoriticists and mineralogists is used in the analysis, there will be a step-change in our understanding of oxygen-rich dust because distinctive features occur only in 5--80 micron observations which cannot be obtained from the ground. I shall use analysis of existing Spitzer data to show that astronomical dust is much more chemically interesting than extra-solar system astrophysicists tend to think. If we knew what the dust was, spectral features could be used to explore metallicity changes within circumstellar environments and between regions within the milky way and to explore the nature of dust in galaxies at high redshft. Observational capability beyond MIRI's 28.5 micron limit would further enhance our knowledge.