Solar System: Things to Know This Week
We love Lucy—our spacecraft that will visit the ancient Trojan asteroids near Jupiter, that is. This week, let us count the ways this 2021 mission could revolutionize what we know about the origins of Earth and ourselves.
Earlier this year, we selected the Lucy mission to make the first-ever visit to a group of asteroids known as the Trojans. This swarm of asteroids orbits in two loose groups around the Sun, with one group always ahead of Jupiter in its path, and the other always behind. The bodies are stabilized by the Sun and Jupiter in a gravitational balancing act, gathering in locations known as Lagrange points.
2. Old. Really, Really Old
Jupiter’s swarms of Trojan asteroids may be remnants of the material that formed our outer planets more than 4 billion years ago—so these fossils may help reveal our most distant origins. “They hold vital clues to deciphering the history of the solar system,” said Dr. Harold F. Levison, Lucy principal investigator from Southwest Research Institute (SwRI) in Boulder, Colorado.
Lucy takes its name from the fossilized human ancestor, called “Lucy” by her discoverers, whose skeleton provided unique insight into humanity’s evolution. On the night it was discovered in 1974, the team’s celebration included dancing and singing to The Beatles’ song “Lucy In The Sky With Diamonds.” At some point during that evening, expedition member Pamela Alderman named the skeleton “Lucy,” and the name stuck. Jump ahead to 2013 and the mission’s principal investigator, Dr. Levison, was inspired by that link to our beginnings to name the spacecraft after Lucy the fossil. The connection to The Beatles’ song was just icing on the cake.
One of two missions selected in a highly competitive process, Lucy will launch in October 2021. With boosts from Earth’s gravity, it will complete a 12-year journey to seven different asteroids: a Main Belt asteroid and six Trojans.
No other space mission in history has been launched to as many different destinations in independent orbits around the Sun. Lucy will show us, for the first time, the diversity of the primordial bodies that built the planets.
Lucy’s complex path will take it to both clusters of Trojans and give us our first close-up view of all three major types of bodies in the swarms (so-called C-, P- and D-types). The dark-red P- and D-type Trojans resemble those found in the Kuiper Belt of icy bodies that extends beyond the orbit of Neptune. The C-types are found mostly in the outer parts of the Main Belt of asteroids, between the orbits of Mars and Jupiter. All of the Trojans are thought to be abundant in dark carbon compounds. Below an insulating blanket of dust, they are probably rich in water and other volatile substances.
This diagram illustrates Lucy’s orbital path. The spacecraft’s path (green) is shown in a slowly turning frame of reference that makes Jupiter appear stationary, giving the trajectory its pretzel-like shape.
This time-lapsed animation shows the movements of the inner planets (Mercury, brown; Venus, white; Earth, blue; Mars, red), Jupiter (orange), and the two Trojan swarms (green) during the course of the Lucy mission.
Lucy and its impressive suite of remote-sensing instruments will study the geology, surface composition, and physical properties of the Trojans at close range. The payload includes three imaging and mapping instruments, including a color imaging and infrared mapping spectrometer and a thermal infrared spectrometer. Lucy also will perform radio science investigations using its telecommunications system to determine the masses and densities of the Trojan targets.
Several institutions will come together to successfully pull off this mission. The Southwest Research Institute in Boulder, Colorado, is the principal investigator institution. Our Goddard Space Flight Center will provide overall mission management, systems engineering, and safety and mission assurance. Lockheed Martin Space Systems in Denver will build the spacecraft. Instruments will be provided by Goddard, the Johns Hopkins Applied Physics Laboratory and Arizona State University. Discovery missions are overseen by the Planetary Missions Program Office at our Marshall Space Flight Center in Huntsville, Alabama, for our Planetary Science Division.
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