Science
The power of MIRI derives directly from the huge gain it makes possible over any preceding method for studying the mid-infrared sky. This gain results from simple physics: 1.) the thermal background for any groundbased telescope blinds mid infrared detectors; and 2.) prior to JWST, cold telescopes in space have been limited in aperture to 0.85m (Spitzer).
The MIRI will be more than 10,000 times faster than even a 30-m infrared-optimized telescope on the ground. It will also be more than 10,000 times faster than SIRTF, with the accompanying gain of far higher angular resolution (with a beam a factor of 50 smaller in area than the one for SIRTF at the same wavelengths).
This unprecedented sensitivity allows the MIRI to make important contributions to all four defining science themes for JWST.
Birth of Stars and Protoplanetary Sytstems
Evolution of Planetary Systems and Conditions for Life.
MIRI overview