  Using the Long Wavelength Spectrometer on Keck I, we have imaged the
gravitationally lensed radio quiet quasi-stellar object (QSO) 2237+0305 at 8.9
and 11.7 microns for the first time. The mid-infrared flux ratios are
inconsistent with the optical flux ratios, but agree with the radio flux ratios
and with some published gravitational lens models. These flux ratios indicate
that the infrared emission is not affected by microlensing, which rules out the
synchrotron emission model. The infrared emission is likely produced by hot
dust extended on a length scale of more than 0.03 parsecs. The spectral energy
distribution further implies a narrow range of dust temperatures, suggesting
that the dust may be located in a shell extending between ~1 to 3 parsecs from
the nucleus, and intercepting about half of the QSO luminosity.
