An Earth-like extra-solar planet is expected to have a luminosity which is many orders of magnitude

less than that of the parent star. We propose a method of identifying molecular spectral bands in light

from such a planet by looking at an off-center part of an interferogram received by FTIR. This can result

in superior sensitivity to narrow spectral bands, which are expected in the planet spectrum, but are

absent in the parent star. We support this idea by simulations, observations and laboratory experiments to illustrate

the method. The results suggest that this method should be applicable to real planet searches.