NASA's Lucy spacecraft will launch in October 2021 on a 12-year journey to Jupiter's Trojan asteroids. The Lucy mission will include three Earth gravity assists and visits to eight asteroids.

Called "Trojans" after characters from Greek mythology, most of Lucy's target asteroids are left over from the formation of the solar system. These Trojans circle the sun in two swarms: one that precedes and one that follows Jupiter in its orbit of the sun. Lucy will be the first spacecraft to visit the Trojans, and the first to examine so many independent solar system targets, each in its own orbit of the sun.

Studying Jupiter's Trojan asteroids up close would help scientists hone their theories on how our solar system's planets formed 4.5 billion years ago and why they ended up in their current configuration. "It's almost like we're traveling back in time," said aerospace engineer Jacob Englander, who helped design Lucy's trajectory while working at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

First conceived seven years ago as a mission to two asteroids, Lucy expanded to epic proportions thanks to creative engineering and impeccable timing.

On Saturn's giant moon Titan, liquid methane and other hydrocarbons rain down, carving rivers, lakes and seas in a landscape of frozen water. The complex chemistry on this icy world could be analogous to the period when life first emerged on Earth, or it might yield an entirely new type of life.