Hubble’s View of Ganymede — Briefing Materials

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Image%20of%20Jupiter%27s%20moon%2C%20GanymedeThis image of Ganymede, one of Jupiter’s moons and the largest moon in our solar system was taken by NASA’s Galileo spacecraft. Credits: NASAM ultimedia Files

NASA is hosting a teleconference at 11 a.m. EDT on Thursday, March 12, to discuss Hubble Space Telescope’s observations of Ganymede, Jupiter’s largest moon. These results will help scientists in the search for habitable worlds beyond Earth.

Speakers/Presenters

  • Jim Green, director of Planetary Science, NASA Headquarters, Washington
  • Joachim Saur, professor for geophysics, University of Cologne, Germany
  • Jennifer Wiseman, Hubble senior project scientist, NASA Goddard Space Flight Center, Greenbelt, Maryland
  • Heidi Hammel, executive vice president, Association of Universities for Research in Astronomy, Washington
     


Figure: 1 — GANYMEDE VIDEO

Caption: This is a video clip of what Ganymede looks like, based on images from NASA’s Galileo orbiter. The US Geological Survey has classified the surface of Ganymede into the types of terrain. The brown regions are those that are heavily cratered and much older than the light shaded regions that are smoother with few craters. These lighter shaded regions are believed to be formed by flooding of the surface with water coming from faults or even cryo-volcanos that have taken place over billions of years. Perhaps even tectonic processes are at work with some crustal ice sheets being forced downward by the emergence of newer icy material. The Galileo spacecraft made six close flybys of the Ganymede and detected a magnetic field coming from the moon itself. In addition, the best models of Ganymede from the Galileo data showed a deep ocean under a thick ice crust. Credit: NASA, USGS


 

Figure: 2 — CUTAWAY OF THE MOON GANYMEDE

CUTAWAY OF THE MOON GANYMEDE

Caption: This is an illustration of the interior of Jupiter’s largest moon Ganymede. It is based on theoretical models, in-situ observations by NASA’s Galileo orbiter, and Hubble Space Telescope observations of the moon’s magnetosphere, which allows for a probe of the moon’s interior. The cake-layering of the moon shows that ices and a saline ocean dominate the outer layers. A denser rock mantle lies deeper in the moon, and finally an iron core beneath that. Credit: NASA, ESA, and A. Feild (STScI)


 

Figure: 3 — GANYMEDE’S MAGNETIC FIELD

This is a sketch of the magnetic field lines around Ganymede, which are generated in the moon’s iron core.

Caption: This is a sketch of the magnetic field lines around Ganymede, which are generated in the moon’s iron core. Hubble Space Telescope measurements of Ganymede’s aurorae, which follow magnetic field lines, suggest that a subsurface saline ocean also influences the behavior of the moon’s aurorae. Credit: NASA, ESA, and A. Feild (STScI)


 

Figure: 4 — GANYMEDE’S AURORAL BELTS- OVERLAY IMAGE

Hubble images of Ganymede's auroral belts (colored blue in this illustration).

Caption: NASA Hubble Space Telescope images of Ganymede’s auroral belts (colored blue in this illustration) are overlaid on a Galileo orbiter image of the moon. The amount of rocking of the moon’s magnetic field provided evidence that the moon has a subsurface saltwater ocean.  Credit: NASA/ESA


 

Figure: 5 — ARTIST CONCEPTION OF GANYMEDE – MAGNETIC FIELDS

In this artist’s concept, the moon Ganymede orbits the giant planet Jupiter.

Caption: In this artist’s concept, the moon Ganymede orbits the giant planet Jupiter. NASA’s Hubble Space Telescope observed aurorae on the moon controlled by Ganymede’s magnetic fields. This field is embedded in Jupiter’s own immense magnetosphere (yellow field lines). A saline ocean under the moon’s icy crust reduces shifting in the auroral belts as measured by Hubble. Credit: NASA/ESA


 

 

Figure: 6 — ARTIST CONCEPTION OF GANYMEDE

Artist concept of Ganymede orbiting Jupiter.

Caption: In this artist’s concept, the moon Ganymede orbits the giant planet Jupiter. NASA’s Hubble Space Telescope observed aurorae on the moon controlled by Ganymede’s magnetic fields. A saline ocean under the moon’s icy crust reduces shifting in the auroral belts as measured by Hubble. Credit: NASA/ESA


 

Figure: 7 — PLOT OF THE ROCKING OF GANYMEDE’S MAGNETIC FIELD

This chart plots the excursion of a pair of auroral belts on Jupiter’s moon Ganymede.

Caption: This chart plots the excursion of a pair of auroral belts on Jupiter’s moon Ganymede. Their motion provides insight into the moon’s interior. Ganymede has a magnetic field produced by an iron core. Because Ganymede is close to Jupiter, it is also embedded in Jupiter’s own magnetic field. When Jupiter’s magnetic field changes, the aurorae on Ganymede also change, “rocking” back and forth. This amount of rocking is inhibited if the moon has a subsurface ocean. By watching the rocking motion of the two aurorae, scientists were able to determine that a large amount of saltwater exists beneath Ganymede’s crust, affecting its magnetic field. Credit: NASA, ESA, and A. Feild (STScI)



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