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Investigating Relative Cloud Heights in Jupiter Using Juno’s JunoCam Imager

Presentation #306.06 in the session New Chemicals, New Clouds, New Toys for Giants.

Published onOct 20, 2022
Investigating Relative Cloud Heights in Jupiter Using Juno’s JunoCam Imager

We describe work to estimate the vertical distances between different cloud and haze layers in Jupiter using images obtained by JunoCam to help us understand their composition and origin. We discuss three different approaches. (1) One approach used images of clouds with shadows. Most of these are compact cumulus-like clouds formed by convection that we call “pop-up clouds”. We measured their heights based on the length of shadows they cast on the underlying cloud deck and knowledge of the relevant geometry. Results suggest heights close to or less than one Jovian scale height above the main cloud deck, comparable to clouds in Earth’s troposphere. We also studied a ~3000-km cyclonic feature we dubbed the Nautilus. Measurements of shadows associated with pop-up clouds in the Nautilus implied altitudes similar to elsewhere in Jupiter. Measurements of long dark regions between the light colored Nautilus and a surrounding darker region, interpreted as shadows, implies altitudes from ~10 to as much as 30 km. Simultaneous observations by the Hubble Space Telescope confirmed that the light regions are higher than their darker surroundings, verifying that these shadows were not albedo changes. (2) We also detected and measured detached hazes at Jupiter’s limb, which have been detected in several of Jupiter’s perijoves and located primarily around 40°N (centric), but ranging between ~25° and 44°N. For example, a detached haze was detected in perijove 43 at a latitude near 43°N. Its altitude and others that have been measured are roughly 80 km above the main cloud deck. If this main deck is associated with condensed NH3, these hazes are located well into Jupiter’s stratosphere. The latitude range of the detached hazes corresponds to the southernmost edges of Jupiter’s prominent North Polar Hood, suggesting that this haze layer is composed of particles forming the hood, which are products of auroral-related chemistry. (3) A parallax method is currently under development. JunoCam recently obtained images showing relative cloud feature displacements that are parallel to vector fields, as expected from parallaxes induced by long-baseline observations of cloud topography rather than from cloud motions. Cutouts of JunoCam images are projected to the same trajectory position, from which a quantitative displacement field is derived. Stereo correspondence is simplified to a one-dimensional search and a digital elevation map of relative cloud heights retrieved.

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