Jupiter: Atmosphere and aurora in unprecedented detail

Image of Jupiter taken on May 18, 2017, one day before the Juno spacecraft's sixth close approach to Jupiter, taken with a filter centered at 8.8 microns that is sensitive to Jupiter's tropospheric temperatures and the thickness of a cloud near the condensation level of ammonia gas. The Great Red Spot appears distinctively at the lower center of the planet as a cold region with a thick cloud layer. It is surrounded by a warm and relatively clear periphery. To its northwest is a turbulent and chaotic region of gas with bands of alternative warm, dry and cold, moist gas. Many other features are also present. This image shows the detailed atmospheric structure of the Great Red Spot and its surroundings that the Juno mission will encounter on its seventh closest approach to Jupiter on July 11, 2017. The instrument used to take these images is Subaru Telescope's facility instrument COoled Mid-Infrared Camera / Spectrometer (COMICS).

Subaru Telescope images reveal weather in Jupiter's atmosphere in the mid-infrared. High-resolution thermal imaging of Jupiter by the COoled Mid-Infrared Camera and Spectrometer (COMICS) mounted on the Subaru Telescope on Maunakea is providing information that extends and enhances the information that the Juno mission is gathering in its unprecedented mission to probe that planet's interior and deep atmospheric structure together with details of the magnetosphere and its auroral interactions with the planet. "The Subaru observations of Jupiter so far this year have been timed to coordinate with the greatest benefit to Juno mission," said Glenn Orton, PI for the portion of the Keck Telescope exchange time with the Subaru Telescope and coordinator for Earth-based observations supporting the Juno project at JPL.

"During our May 2017 observations that provided real-time support for Juno's sixth perijove, we obtained images and spectra of the Great Red Spot and its surroundings. Our observations showed that the Great Red Spot, the largest known vortex in the solar system, had a cold and cloudy interior increasing toward its center, with a periphery that was warmer and clearer. This implied that winds were upwelling more vigorously toward its center and subsiding on the periphery. A region to its northwest was unusually turbulent and chaotic, with bands that were cold and cloudy, alternating with bands that were warm and clear bands. This region is where air heading east toward the Great Red Spot flows around it to the north, where it encounters a stream of air flowing over it from the east," adds Orton. "This information will allow us to determine the three-dimensional structure of winds that are otherwise only tracked in two dimensions using cloud features in reflected sunlight." "A wide variety of filters installed in COMICS is advantageous in sensing Jupiter's temperatures in its upper troposphere and in its stratosphere," noted co-investigator and Subaru Telescope staff astronomer Takuya Fujiyoshi.

Juno has now made five close-up passes of Jupiter's atmosphere, the first of which was on August 27, 2016 and the latest (the sixth) on May 19 of 2017. Each of these close passes has provided Juno's science team with unexpected surprises, and the Juno science return has benefited from a coordinated campaign of Earth-based support. This campaign includes observations from spacecraft near or orbiting the Earth, covering X-ray through visible wavelengths and ground-based observatories covering near-infrared through radio wavelengths.

Another set of supporting observations that were simultaneous with the Subaru observations were made by the Gemini North telescope's NIRI instrument, which imaged Jupiter in the near-infrared, measuring reflected sunlight from cloud and haze particle in Jupiter's upper troposphere and lower stratosphere -- levels generally higher in Jupiter's atmosphere than most of the Subaru measurements, providing complementary information. "Wide coverage of wavelength available from the telescopes on Maunakea is thus advantageous for the study," Fujiyoshi says.

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