On December 30, NASA's Juno spacecraft, which has been orbiting Jupiter for the better part of a decade, made its closest flyby of Io, the innermost moon in the Jovian system.
The spacecraft came to within 930 miles (1,500 km) of the surface of Io, a dense moon that is the fourth largest in the Solar System. Unlike a lot of moons around Jupiter and Saturn, which have surface ice or subsurface water, Io is a very dry world. It is also extremely geologically active. Io has more than 400 active volcanoes and is therefore an object of great interest to astronomers and planetary scientists.
Read more about the flyby here.
