Ganymede is the largest moon in our solar system and the only moon with its own magnetic field creating energetic charged particles that cause gases to light up like those we see on Earth. Joachim Saur of the University of Cologne released in a news release that after he asked himself the question of whether you could use a telescope to look inside a planet’s body, he thought of 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,” he said.
By using Hubble space telescope to measure the slight shifts of two auroras, Saur and his research team found that a large volume of saltwater exists underneath Ganymede’s crust of ice. If you’re a little lost at this point; you’re not alone! It’s a lot of information to get one’s head around, but if you look at the image below, you can see the pair of auroral belts encircling over the northern and southern mid-latitudes of Ganymede. Ocean on Jupiter’s moon auroraThe auroral belts were observed in ultraviolet light by the Space telescope imaging spectrograph, highlighted blue.