The most volcanically active world in the entire solar system has recently been imaged by NASA's Juno spacecraft during a close fly-by.
That world is none other than Jupiter's moon, Io, and during a close fly-by, the Juno spacecraft captured the volcanically active body at a distance of just 930 miles. Notably, Io is a "tortured moon" as it's constantly engaged in a gravitational tug of war between Jupiter and the two neighboring moons, Europa and Ganymede. The result of being stuck in the middle is friction across the entire world, and when you have friction, you get heat.
The surface of Io is scorched by this intense heat that is further exacerbated by extreme volcanic activity, with recent estimates pointing to more than 400 active volcanoes littered across the surface of the moon. NASA's Juno spacecraft managed to capture some of the plumes of gas erupting into space from these volcanoes. Furthermore, Io's volcanoes aren't like the volcanoes here on Earth; they are much larger - in fact, Io's largest volcano, Loki Patera, is approximately twice the size of Earth's largest volcano, Mauna Loa.
"The tidal forces generate a tremendous amount of heat within Io, keeping much of its subsurface crust in liquid form seeking any available escape route to the surface to relieve the pressure. Thus, the surface of Io is constantly renewing itself, filling in any impact craters with molten lava lakes and spreading smooth new floodplains of liquid rock," writes NASA on its website