On Sept. 29, NASA's Juno probe will perform the closest flyby of Jupiter's icy moon Europa in over 20 years as the spacecraft embarks on a mission to probe deep into Europa's ice in search of pockets of liquid water.

Europa contains a global ocean beneath a solid crust of ice, making this moon one of the most intriguing places in the solar system to search for extraterrestrial life and one of astrobiologists' top priorities. Although Juno won't be able to tell us whether Europa harbors alien life, it will teach us more about the moon's icy crust, such as how thick it is and whether there are any subsurface pockets of liquid water that could reach the surface.

Juno arrived at Jupiter in July 2016, and its mission has focused on studying Jupiter's atmosphere, from the heights of its ruddy-brown cloud tops to the depths of the lower cloud layers hundreds of miles down, as well as learning about the gas giant's powerful magnetic field and its interior structure all the way down to its core.