The Dust Sequence along the AGB

We present a preview of a Spitzer-IRS program aimed to study the formation and evolution of dust in the outflows of oxygen-rich stars as they climb the Asymptotic Giant Branch (AGB). Previous studies were generally biased to bright, nearby stars which provided studies limited to a biased and inhomogeneous sample of stars. The unique sensitivity of Spitzer-IRS now allows to carefully select a homogeneous sample of stars along the AGB at the same distance and with comparable progenitor masses, thereby greatly limiting the remaining parameters of importance for the process of dust formation. We present here how this program will help to understand mass loss evolution and dust formation mechanisms around evolved stars.