The term Trojan asteroid refers to any asteroid caught near the gravitationally stable L4 and L5 points (Lagrangian points) in any planet-sun system in our solar system. Mars and Earth both have Trojans, but, not surprisingly, the biggest planet Jupiter has the greatest number of them, with perhaps as many Trojan asteroids orbiting 60 degrees ahead of and behind Jupiter in its orbit as in the better-known asteroid belt between Jupiter and Mars. NASA said this week (October 30, 2018) that it has now given the nod to its first space mission to Jupiter’s Trojans. It’s a reconnaissance mission, called Lucy, now approved by NASA for a 2021 launch. NASA said:
The confirmation review, formally known as Key Decision Point C, authorized continuation of the project into the development phase and set its cost and schedule. The confirmation review panel approved the detailed plans, instrument suite, budget and risk factor analysis for the spacecraft.
The next major mission milestone, the Critical Design Review, will examine the detailed Lucy system design. After a successful critical design review, the project team will assemble the spacecraft and its instruments.
Lucy Principal Investigator Hal Levison of the Southwest Research Institute at Boulder, Colorado, commented:
Up until now this mission has entirely been on paper. Now we have the go-ahead to actually cut metal and start putting this spacecraft together.
The Lucy mission to Jupiter’s Trojans takes its name from the fossilized human ancestor called Lucy, which has been dated to some 3.2 million years ago. The skeleton of the fossil Lucy provided unique insight into human evolution. Likewise, NASA said:
… the Lucy mission will revolutionize our knowledge of planetary origins and the formation of the solar system.
Lucy is planned for launch in October 2021. During its 12-year journey, the spacecraft will visit seven different asteroids – a Main Belt asteroid and six Trojans. The spacecraft and a remote-sensing instrument suite will study the geology, surface composition, and bulk physical properties of these bodies at close range.
Bottom line: The Lucy mission to Jupiter’s Trojan asteroids has passed a critical hurdle and is on its way to a 2021 launch.