The SOFIA airborne telescope observes Jupiter

Left: Optical image of Jupiter taken by the Hubble Space Telescope. Right: SOFIA image of Jupiter showing the variation of its brightness temperature with latitude. Both images show Jupiter in approximately the same orientation. Image Credit: Left: NASA/ESA; Right: NASA/SOFIA/de Pater et al., 2021

Planetary scientists have used the Stratospheric Observatory for infrared astronomy (SOFIA), a joint project of " data-gt-translate-attributes="[{" attribute="">Nasa and the German Space Agency at DLR, to examine Jupiterthe planet’s atmospheric circulation — for the first time during the planet’s boreal winter — during flights in August 2018 and July 2019.

To do this, they looked at hydrogen.

Hydrogen molecules – H2 – can be arranged in two different ways, called parahydrogen and orthohydrogen. The two orientations have distinct energies, so determining the ratio of parahydrogen to orthohydrogen can tell astronomers the global temperature.

The researchers examined the concentration of parahydrogen and orthohydrogen at altitudes just above Jupiter’s main cloud deck. They discovered that around the equator hot gas rises in the Jovian atmosphere. At the north and south poles, however, the reverse happens: cold gas from the upper and cooler levels of the atmosphere moves downward.

“It gives an idea of ​​the general circulation: rising at the equator, descending near the poles,” said Imke de Pater, lead author of a recent paper in the Journal of Planetary Science describing the observations.


SOFIA flies over the snow-capped Sierra Nevada Mountains with its telescope door open during a test flight. SOFIA is a modified Boeing 747SP. Credit: NASA/Jim Ross

Jupiter’s atmosphere had already been observed through the lens of hydrogen – by SOFIA in 2014, and by NASA Voyager 1 and 2 in 1979 – but only during the northern Jovian summer. The current observations are the first ever taken during Jupiter’s boreal winter, about half a Jovian year after the 2014 SOFIA studies. This comparison illustrates how Jupiter’s poles change with the seasons, showing that its far north remains cooler than its extreme south, whatever the time of year.

Jupiter’s northern and southern hemispheres are known to have an asymmetric aerosol distribution, so this temperature imbalance between its two poles is likely an effect of its asymmetry.

While studying Jupiter, de Pater and his colleagues also saw four other objects that had entered SOFIA’s field of view and collected data: Jupiter’s four largest moons, known collectively as the Galilean satellites – Io, Europe, Ganymedeand Callisto.

“We were surprised to have captured all four satellites and to be able to determine their brightness temperature,” de Pater said.

Thanks to this pleasant surprise, the group was able to clearly see how the temperatures of the moons decrease with depth in their underground layers. These temperature changes can potentially be used to determine the composition, density, and other properties inside satellites.

The satellites all have unique characteristics – ranging from water ice on Europa, to heavy craters on ancient Callisto, to extreme volcanic activity on Io – making their material composition particularly interesting to study.

Jupiter and its moons are too bright to be observed by the long-wavelength channels on the James Webb Space Telescope because they can saturate the instrument and they cannot be measured from the ground because the Earth’s atmosphere blocks a large amount of mid-infrared radiation. SOFIA’s unique access to mid-infrared therefore enables these measurements and provides essential information about Jupiter and its moons.

Reference: “SOFIA observations of variability in Jupiter’s Para-H2 Distribution and Underground Emission Characteristics of Galilean Satellites” by Imke de Pater, Leigh N. Fletcher, William T. Reach, Charles Goullaud, Glenn S. Orton, Michael H. Wong and Robert D. Gehrz, November 10, 2021, Journal of Planetary Science.
DOI: 10.3847/PSJ/ac2d24

SOFIA is a joint project of NASA and the German Space Agency at DLR. The DLR provides the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science, and mission operations in cooperation with the Space Research Association of Universities, headquartered in Columbia, Maryland, and the German SOFIA Institute at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703 in Palmdale, California.

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