The NIR transmission spectrum of Jupiter from the observation of a Ganymede’s eclipse

Abstract

Here, we report the NIR transmission spectrum of Jupiter, with high signal-to-noise ratio, as if it were a transiting planet. Our technique was to observe Ganymede, when crossing Jupiter’s shadow. During the eclipse, the spectral features of the Jovian atmosphere are imprinted in the sunlight that, after passing through Jupiter’s planetary limb, is reflected from Ganymede towards the Earth. The ratio spectrum of Ganymede before and during the eclipse removes the spectral features of the Sun, the local telluric atmosphere on top of the telescopes, and the spectral albedo of Ganymede. Ganymede is a practically atmosphere-less body and do not suffer any significant weather variability.