Ganymede, the largest moon of the solar system, may have an ocean beneath its surface. This claim scientists in response to observations with the Hubble Space Telescope. The ocean is more than 150 kilometers below the crust of Jupiter’s moon.
Although Ganymede is larger than the planet Mercury and the large Saturn’s moon Titan, Io and Europa are his brothers often in the spotlight. Io looks like a pizza and is very volcanically active. Europe has a giant ocean below the surface and may be a breeding ground of (microscopic) life. Ganymede appears at first sight a fairly boring, cratered moon.
But appearances are deceptive, as it turns out. Ganymede is the only moon in the solar system its own magnetic field. Suppose an astronaut walking on the surface of Ganymede, so he can see auroras. Observations with the Hubble telescope show that the aurora swaying. From computer models, it appears that the rocking movement would have to be much larger. Why is this not so? According to the researchers, this is due to the water beneath the 150 kilometer thick crust of Ganymede. There arises a secondary magnetic field that opposes the field of Jupiter, thus rocking the auroras not six, but only two degrees.
Scientists suspect that the ocean hundreds of kilometers deep. If this is so, Ganymede is the largest ocean in the solar system. Earth’s oceans are up to ten miles deep. The oceans on Europa and Enceladus are not much deeper.
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