  Mid-infrared observations of the Andromeda galaxy, M31, obtained with the
Infrared Array Camera on board the Spitzer Space Telescope, are presented. The
image mosaics cover areas of approximate 3.7deg x 1.6deg and include the
satellite galaxies M32 and NGC 205. The appearance of M31 varies dramatically
in the different mid-infrared bands, from the smooth bulge and disk of the old
stellar population seen at 3.6um to the well-known '10 kpc ring' dominating the
8um image. The similarity of the 3.6um and optical isophotes and nearly
constant optical-mid-infrared color over the inner 400 arcsec confirms that
there is no significant extinction at optical wavelengths in M31's bulge. The
nuclear colors indicate the presence of dust but not an infrared-bright
nucleus. The integrated 8um non-stellar luminosity implies a star formation
rate of 0.4 Msun/yr, consistent with other indicators that show M31 to be a
quiescent galaxy.
