Lucy Mission Launches To Study Ancient Trojan Asteroids

~ By Htoo Myat Noe

A 12 year mission with a coverage of nearly 4 billion miles, an exploration of some of the solar system’s oldest celestial objects that are speculated to be as old as the solar system itself, a $981 million study of the Trojan asteroids within Jupiter’s orbit -- here’s everything you need to know about NASA’s Lucy.  On 16 October 2021 at 5.34am ET, NASA’s Lucy spacecraft launched from Cape Canaveral Air Force Station in Florida to claim the title of the first NASA mission ever to explore the Trojan asteroids. Located within Jupiter’s orbit, the asteroids are believed to hold clues to the early solar system, and maybe even the origin of life itself since many scientists have ascertained that the mission will help the community better understand the processes that brought organic matter and water, the essential, primary building blocks of life, to Earth. The uncrewed spacecraft sat atop a United Launch Alliance Atlas V 401 rocket, as the science community worldwide crossed their fingers and eagerly awaited the commencement of this unprecedented mission. The spacecraft will make 2 slingshot trips, also known as passes, around the Earth before it enters Jupiter’s orbit, one pass in 2022 and the other in 2024, for the additional gravitational thrust. This is known as the gravitational slingshot effect where the spacecraft will utilise the gravitational attraction of the planet to obtain some of the momentum of the planet to transfer it to itself. (Quora, 2017) The outline of the slingshot trips, as well as the 2 distinguishable clusters of the Trojan asteroids within Jupiter’s orbit at the 2 Lagrange points can be observed below. 

Many have the misconception that Lucy is going near Jupiter, which is, as suggested, a misconception as Lucy will not be going anywhere near Jupiter! The Jupiter Trojan asteroids orbit the Sun in two loose but discernible clumps, one in front of Jupiter’s orbital path and the other behind, as seen in the diagram below.

These asteroids are packed together at two Lagrange points, in which the distance to Jupiter and the Sun are approximately equal. The Trojan asteroids are trapped in stable orbits and have actually been that way for billions of years! As explained by NASA, the Lucy spacecraft was named after the famous Australopithecine fossil found in 1974, an ancient fossil that “provided unique insight into humanity’s evolution,” and likewise, “the Lucy mission will revolutionize our knowledge of planetary origins and the formation of the solar system.” Paleontologists had named the Lucy fossil after the Beatles’ song, “Lucy in the Sky With Diamonds,” making the spacecraft’s name even more fitting. Many may be wondering what the timeline of the mission will be like. Firstly, the spacecraft will go by a small asteroid named “Donald Johanson” in 2025. Donald Johanson discovered the Lucy Australopithecus fossil, and when an MIT graduate student discovered this unnamed asteroid on Lucy’s flight path, MIT was able to get the asteroid named after him. Then, after the spacecraft passes by Donald Johanson in the main belt, it will finally reach one of the clouds of Trojan asteroid in August 2027. There are 2 groups of Trojan asteroids (refer to previous 2 diagrams), both of which are in orbit, 60 degrees in front, and 60 degrees in the back of Jupiter. The spacecraft will be in the leading group of Trojan asteroids, called the L4 Lagrange point, in 2027. And then in 2030, the spacecraft will swing back around to the Earth, to go to the other side of Jupiter to get to the second cloud of Trojan asteroids on the other side of Jupiter in 2033.

Lucy will study three different types of asteroids: C, P, and D. C-type asteroids are common in the outer realms of the Main Belt between Mars and Jupiter, while P-type and D-type asteroids are similar to the icy Kuiper Belt objects from beyond the orbit of Neptune. All Trojans are believed to contain high levels of dark carbon compounds and even volumes of water and other volatile compounds. C-type asteroids are chondrite, common ancient asteroids made of clay and silicate, D-type asteroids are asteroids with low albedos (meaning low percentage of reflected radiation, or reflectivity) and may be rich in organic molecules. Lastly, P-type asteroids are asteroids that also have low albedos and have generally featureless reddish spectra. (Howell, 2021) Lucy is equipped with several instruments, such as a color visible imager to determine composition, a Lucy’s LOng-range reconnaissance imager (L'LORRI) thought to pick up high-resolution images of small details on each asteroid's surface even at expected distances of 1000km, a thermal emission spectrometer to examine how the Trojans retain heat, a terminal-tracking camera to obtain wide-field images of the asteroids to learn more about their shapes and a high-gain antenna to determine the masses of each of these mysterious small worlds. (Dvorsky, 2021) The mission’s principal investigator is Hal Levison from the SouthWest Research Institute (SWRI) whose principal research interests lie in the area of the long-term dynamics of astronomical objects. Dr. Levison's work includes studies of the formation of both giant and terrestrial planets, the long-term dynamical behavior of comets, the dynamics of objects in the Kuiper belt, the origin and stability of Trojan asteroids, and the formation of satellites. In 1997 he aided in the prediction of the existence of the Scattered Comet Disk. He is perhaps best known, however, for his work on the early dynamical evolution of the outer Solar System, and is an author of the most comprehensive model to date. (Harold F. Levison, n.d.) The mission’s second-in-command as the deputy principal investigator is none other than Cathy Olkin, who received her bachelor’s degree from the Massachusetts’ Institute of Technology (MIT) Department of Aeronautics and Astronautics (AeroAstro) and her doctorate degree from the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS). She is a planetary scientist with interests in icy outer solar system worlds and she uses near-infrared spectroscopy to study icy surfaces and stellar occultations to investigate tenuous atmospheres. What’s more, she is also the lead for the Ralph instrument on NASA’s New Horizons mission to Pluto! (Cathy Olkin, n.d.) A project scientist Richard Binzel, professor of planetary sciences in MIT EAPS with a joint appointment in MIT AeroAstro even mentioned that the first paper he published on Trojan asteroids was with an MIT Undergraduate Research Opportunity Program (MIT UROP) student, and that it was a truly surreal experience to put his learnings to practice and make new breakthroughs in the community -- an inspiring story indeed. (Q&A: Lucy Mission Launches to Study Ancient Trojan Asteroids, n.d.) (The picture below is that of Levison and Olkin)

The last fact about Lucy is one that many may not be aware about, and it is one that I think is a rather endearing addition to the features of the Lucy spacecraft -- a special plaque is coming along for the 12 year ride.The Lucy Mission is carrying a message for our own descendants! After the mission is over, the Lucy spacecraft will remain on a stable orbit, travelling between the Earth and the Trojan asteroids for hundreds of thousands of years, so it is not completely out of the question and our imagination that some day in the distant future, our descendants may retrieve the Lucy spacecraft as a relic of the early days of humanity’s exploration of the Solar System. In addition to a diagram of our solar system’s planets, the plaque contains messages from key 20th century thinkers, including Albert Einstein, Martin Luther King Jr., and Carl Sagan, just to name a few. (The Lucy Plaque, n.d.)

There have been many missions that have been sent out to space, beyond Earth’s orbit and even beyond the Solar System over the decades, and the Lucy mission is just one of them. There is no doubt that we are still at the first steps of space exploration and we have a vast, endless journey ahead of us, worlds upon worlds of celestial objects that we may be all-knowledgeable about one day, or (in a much less fortunate future) we may miss out on. Nevertheless, missions like Lucy that bring hope to the community, from the principal researchers of the mission itself, to other professionals working in the field, to youths like us with a dream to grasp onto a future not quite far away, all the way to the little ones in the audience with the curious spark in their eyes cheering the spacecraft on as it lifted off, should be celebrated, if not for the mysteries of the universe they aim to solve, then for the hope they provide for the space nerds on our Blue Marble who just want a brighter future for us.