Synthetic spectrum in reflection (left) and thermal emission (right) during secondary transit of a Gl 581 c like planet with a 200 mb atmosphere at 10 parsecs. The black solid and the gray dashed lines respectively stand for the dry collapsed and runaway case presented in Fig. 8. Thin dashed lines in the emission part correspond to blackbody spectra at the temperatures indicated. In the runaway case, water is abundant in the atmosphere and H₂O absorption bands are noticeable throughout the spectrum (between 5 and 9 μm in the emission spectrum and above 0.7 μm in reflection). The shift in the thermal emission toward shorter wavelengths due to the much hotter surface is also striking.