W43 - Extreme Star Formation in the Galactic Bar

We propose to extend Spitzer's study of massive star formation to the W43 massive star-forming complex, located in the 5 kpc molecular ring, which is the most active region of star formation in our Galaxy. Star formation may be different in this region due to a higher overall density of massive molecular clouds and star formation, higher radiation fields and supernova rates, and a higher metallicity. Thus, the proposed observations will allow us to compare star formation in this massive inner Galaxy region to star formation near the Sun, and in the outer Galaxy (coming from the studies of W5, the Cycle-5 SMOG project, and GLIMPSE360), and therefore to complete a more representative view of star formation in the Galaxy.