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Water on Jovian Moon seen by Hubble


Scientists are estimating that the ocean is 100 km wide and it is located underneath 150 kilometers of crust, especially ice. In fact, this result appears to confirm a hypothesis which already existed since 1970, then repeated thanks to NASA’s Galileo spacecraft which measured the magnetic field of Ganymede in 2002.
The largest of the moons of Jupiter is called Ganymede, and it is one of the so-called Mediceean moons, how their discoverer, Galileo Galilei wanted to define them. Ganymede is the only moon that has its own magnetic field, which produces auroras at its poles, in close relation with the magnetic field of Jupiter.

Ganimede-un-sandwich-di-oceani-e-ghiaccio5

Credit: NASA

Through them, but mostly thanks to the versatility as well as the capacity of the most famous space telescope in the world, the Hubble Space Telescope, NASA’s men have confirmed the hypothesis that Ganymede is hiding an underground ocean of water much larger than the oceans of Earth combined.
“This discovery marks a significant milestone and highlights the potential of Hubble,” said John Grunsfeld, deputy administrator of the Science Mission Directorate at NASA. “In his 25 years in orbit, Hubble has made many scientific discoveries in our solar system. An ocean deep beneath the icy crust of Ganymede opens more interesting possibilities for life beyond Earth. ”
In fact, identifying liquid water is crucial in the search for habitable worlds beyond Earth and to the search for life as we know it.
As we said, the magnetic field of Ganymede is related to that of Jupiter and when the second is changing, it causes an oscillation of the aurora on the moon, a sort of rocking. Thanks to Hubble, it has been possible to study this oscillation to learn more about the interior of this Jovian satellite.
“I always wondered how we could use a telescope in other ways,” said Joachim Saur at the University of Cologne. “Is there a way we could use a telescope to look inside a planetary body? Then I thought… the aurora! Because auroras are controlled by the magnetic field, if you look properly, you learn something about the magnetic field. If you know the magnetic field, then you know something about the interior of the moon. ”
If it was this an ocean of salt water, the magnetic field of Jupiter would create a secondary magnetic field in the ocean that would contrast that of the gaseous planet. This “magnetic friction” would have to slow down the rocking of the auroras. And indeed this alleged underground ocean “fights” the Jovian magnetic field so strongly as to reduce the rocking of the aurora to 2 degrees, instead of the estimated 6 degrees in the absence of this underground ocean.
Scientists are estimating that the ocean is 100 km wide and it is located underneath 150 kilometers of shell, especially ice. In fact, this result appears to confirm a hypothesis which already existed since 1970, then repeated thanks to NASA’s Galileo spacecraft which measured the magnetic field of Ganymede in 2002.

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