Page 4 - GC-May-June-2022

SOFIA's observations of Jupiter

present a "Jovial" surprise

To study the atmospheric circu- During flights in August 2018
thohydrogen can tell astronomers
lation on Jupiter, researchers ob- and July 2019, planetary scientists
about the overall temperature.
served the hydrogen near Jupiter's used the Stratospheric Observatory
The researchers studied the con-
upper troposphere. In doing so, they for Infrared Astronomy (SOFIA), a
centration of parahydrogen and or-
noticed that Jupiter's four moons – joint project of NASA and the Ger-
thohydrogen at altitudes just above
the Galilean satellites – had entered man Space Agency at DLR, to study
Jupiter's main cloud deck. They dis-
their field of view and they were the atmosphere on Jupiter. To do covered that, around the equator,
able to capture the temperature vari- this, they looked at hydrogen.
warm gas is rising into the atmo-
ations in the subsurface layers of Hydrogen molecules – H2 – can sphere. At the north and south poles,
these four satellites as well. The be arranged in two different ways, At left: Optical image of Jupiter taken by the Hubble Space Tele-
however, the opposite is occurring:
results were published in a recent known as parahydrogen and ortho- Cold gas from the higher, cooler scope. At right: SOFIA image of Jupiter demonstrating the variation
paper in the Planetary Science Jour- hydrogen. The two orientations in its brightness temperature with latitude. The two images show
levels of the atmosphere is traveling
nal describing the observations. have distinct energies, so determin- downward. Jupiter in approximately the same orientation.
ing the ratio of parahydrogen to or- Image credit: Left: NASA/ESA; Right: NASA/SOFIA/de Pater et al., 2021
"This gives a sense of the gener-
al circulation: rising at the equator,
sinking near the poles," said Imke
de Pater, lead author of the paper. About SOFIA
SOFIA is an 80/20 partnership
Jupiter's atmosphere had been
studied through the lens of hydro- of NASA and the German Aero-
space Center (DLR), consisting of
gen before – by SOFIA in 2014, and
by NASA's Voyager 1 and 2 in 1979 an extensively modified Boeing
747SP aircraft carrying a 2.7-me-
– but only during the northern Jo-
vian summer. The current observa- ter (106 inch) reflecting telescope
(with an effective diameter of 2.5
tions were the first ever taken
during Jupiter's northern winter, meters or 100 inches). The aircraft
is based at NASA's Armstrong
about half a Jovian year after the
2014 SOFIA studies. This compari- Flight Research Center in Palm-
dale, Calif. The SOFIA Program
son illustrated how Jupiter's poles
change with the seasons, showing Office is at NASA Ames Research
Center in Moffett Field, Calif.,
that its far north remains cooler than
its far south, regardless of time of which manages SOFIA's science
and mission operations in cooper-
year.
Jupiter's northern and southern ation with the Universities Space
Research Association (USRA;
hemispheres are known to have an
asymmetric aerosol distribution, so Columbia, Md.) and the German
SOFIA Institute (DSI; University
this temperature imbalance between
its two poles is likely an effect of its of Stuttgart).
asymmetry.
In studying Jupiter, de Pater and
ice on Europa, to heavy craters on
her colleagues also saw four other
objects that had entered SOFIA's the ancient Callisto, to extreme vol-
canic activity on Io – making their
field of view and the data collected:
Jupiter's four largest moons, known material makeup particularly inter-
esting to investigate.
collectively as its Galilean satellites
Jupiter and its moons are too
– Io, Europa, Ganymede, and Calli-
bright to be observed by the long
sto.
wavelength channels on the James
"We were surprised that we ac-
Webb Space Telescope as they can
tually captured all four satellites,
saturate the instrument, and they
and could determine their brightness
cannot be measured from the
temperature," de Pater said.
ground due to Earth's atmosphere
Thanks to this pleasant surprise,
blocking a large amount of mid-in-
the group could clearly see how the
frared radiation. SOFIA's unique
moons' temperatures decrease with
access to the mid-infrared, there-
depth in their subsurface layers.
fore, enables these measurements
These temperature changes can
eventually be used to determine the and provides critical information
about Jupiter and its moons.
composition, density, and other
properties inside the satellites. - Universities Space Research
Association
The satellites all have unique
characteristics – ranging from water