If we cannot spatially separate an exoplanet and its star on a telescope, we might still be able to do spectroscopy if we can subtract the background the light form the star makes. As the star should be black body radiation, with just hydrogen and helium lines superimposed, we should be able to model that background very well. So we could subtract the expected background from the measured background and whatever is left over should be from the planet(s).
If we go to the peak wavelength of a black body at 300K (around 10µm), the signal of a sun-like star at 6000K should be just 25 times brighter than an earth-like planet at 300K. This should be measurable, and at least the temperature of the planet could be measured that way.
But combing that signal for spectral lines of organic molecules would be an extremely ugly task. It might be interesting to calculate how long one would have to measure under ideal conditions, but I think this would not be a quick measurement in any way.
If we go to the peak wavelength of a black body at 300K (around 10µm), the signal of a sun-like star at 6000K should be just 25 times brighter than an earth-like planet at 300K. This should be measurable, and at least the temperature of the planet could be measured that way.
But combing that signal for spectral lines of organic molecules would be an extremely ugly task. It might be interesting to calculate how long one would have to measure under ideal conditions, but I think this would not be a quick measurement in any way.
