Ganymede: a moon bigger than a planet

Curious facts

1. 01

   Bigger than Mercury

   It is the largest moon in the Solar System, bigger than the planet Mercury (in size, not in mass) and than Pluto. It is also the only moon with its own magnetic field. ¹

2. 02

   Its auroras gave away an ocean

   That magnetic field gives it auroras around its poles. In 2015 the Hubble telescope saw that they rocked by only 2 degrees instead of 6: something was holding them back, and the explanation is a salty ocean under the ice. ²

3. 03

   An ocean ten times deeper

   By NASA’s estimate, that ocean would be about 100 km deep, ten times deeper than Earth’s, under a crust about 150 km thick. ²

4. 04

   The first spacecraft to orbit another moon

   ESA’s Juice probe reaches Jupiter in July 2031 and in December 2034 will go into orbit around Ganymede. It will be the first spacecraft ever to orbit a moon other than our own. ³