Underground ocean found on Jupiter’s largest moon
10 Apr 2015 by qmjwtjwqdb.d qmjwtjwqdb.d
Scientists have used a new approach to find evidence for a subsurface saltwater ocean on Jupiter's largest moon.
By using the NASA’s Hubble Space Telescope, researchers at University of Cologne in Germany have discovered that aurorae – optical emissions caused by solar particles penetrating a magnetosphere – provide evidence for the presence of an underground ocean on Ganymede.
Ganymede is the largest moon in our solar system and the only moon with its own magnetic field. The magnetic field causes aurorae in regions, circling the north and south poles of the moon which oscillate due to Jupiter's varying magnetospheric field.
Professor Joachim Saur at the University of Cologne said: “I was always brainstorming how we could use a telescope in other ways. Is there a way you could use a telescope to look inside a planetary body? Then I thought the aurorae! Because aurorae are controlled by the magnetic field, if you observe the aurorae in an appropriate way, you learn something about the magnetic field. If you know the magnetic field, then you know something about the moon's interior”.
In the study, published in the Journal of Geophysical Research, the team observed and modelled the dynamics of the auroral ovals of Ganymede. By observing the change of the aurorae, the team were able to determine that a large amount of saltwater exists beneath Ganymede's crust.
The scientists found that the locations of the ovals oscillate on average by 2.0° and predicted a significantly stronger oscillation up to 5.8° without the presence of an ocean. They also estimated the thickness of the ocean to be 100 km – 10 times deeper than Earth's oceans – and to be buried under a 150 km crust of mostly ice.
“This discovery marks a significant milestone, highlighting what only Hubble can accomplish. A deep ocean under the icy crust of Ganymede opens up further exciting possibilities for life beyond Earth,” said John Grunsfeld, associate administrator of NASA's Science Mission Directorate at NASA Headquarters.
Paper: http://onlinelibrary.wiley.com/doi/10.1002/2014JA020778/pdf
