How high are Jupiter’s clouds? Analysis of JunoCam images of the “Nautilus”

Jupiter is known for its active meteorology and stormy weather, but still remaining are the questions how high are its clouds and what are they made of? Using images acquired by JunoCam, Juno’s visible light camera, we analyze the length of the clouds’ shadows to infer their heights. We focus on the “Nautilus” a 3000-km cyclonic vortex seen during Juno’s 14th perijove and observed simultaneously with the Hubble Space Telescope. We show that individual clouds or cloud fronts with typical lengths of ∼200 km extend about ∼10 to 20 km above the deeper surrounding cloud deck. That white cloud deck forms the spiral of the cyclone, which we show lies ∼20 to 30 km above a reddish-colored region. An analysis of the HST images confirms that the white region is higher than its surrounding darker, reddish cloud deck. These respective elevations are consistent with the white clouds being made of fresh ammonia ice while most of the reddish clouds underneath are made of ammonium hydrosulfide NH₄SH, as predicted by equilibrium cloud models.