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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
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