Mg ii lines spectral region (Mg ii-k line at 2796.35 Å and Mg ii-h line at 2803.53 Å). The spectrum is observed during the two first transits. The average of orbits #2 and #5 (blue line) represents the Out of transit spectrum, while the average of orbits #3 and #4 (red line) represents the In transit spectrum. Wavelengths are transformed into velocity shifts relative to the Mg ii-k line (individual pixels correspond to about 5 km s^-1 bandwidth).