Next year, NASA and the Southwest Research Institute will launch Lucy, a 13-meter-long spacecraft with two vast solar panels and an array of imaging and spectroscopy instruments. Named after the Australopithecus fossil which revealed a new understanding of human evolution, the Lucy mission hopes to similarly revolutionize our understanding of the evolution of the solar system by visiting the Trojan asteroids of Jupiter.
Digital Trends spoke with Hal Levison, principle investigator of the Lucy project, about how the mission to visit these asteroids could reveal clues about the formation of our solar system and could even offer insights into the origin of life on Earth.
Asteroids aplenty
Although we know a reasonable amount about asteroids in these first two locations thanks to missions like Dawn and New Horizons, the Trojans remain objects of mystery.
One reason little is known about the Trojans is that these other locations contribute to meteorites which crash to Earth. We can go and literally pick up pieces of these asteroids from other locations in the solar system. But Trojans don’t send meteorites to Earth, so we have no way of knowing what these bodies are like — unless we go and visit them.
A time capsule of the early solar system
The Trojans are believed to be remnants of the ancient material which formed the outer planets at the dawn of our solar system. That means they act as “time capsules,” and studying them gives astronomers an opportunity to look back to a period more than 4 billion years ago.
Not only can the Trojans tell us about the formation of the outer planets, but they may even give us clues about the origin of life on Earth. Scientists know that water on Earth, essential for the development of life, must have come from somewhere off-planet as the early inner solar system was too hot for water to condense. One theory is that water was carried to Earth from the outer solar system, and that asteroids like the Trojans could have transported it.
The diversity is the mystery
Lucy will be visiting the Trojans in the orbit of Jupiter, where they are corralled by the planet into a stable orbit.
The Trojans are notable for one unusual feature: They are highly diverse, coming in different shapes and sizes and, importantly, appearing to be different colors. Scientists think that these variations imply that the Trojans could come from a variety of different sources.
“The diversity of the Trojans is the real mystery,” Levison said. “Even from the ground, these objects look very different. Some are grey, some are sort of red, and some are very red. We’re not sure what this redness means. This could be telling us that the objects formed in different areas of space.”
Only around 7% of the Trojans are gray, leading to two possibilities. “Either red objects are fragile and disintegrate on impact,” Levison explained. “Or whatever makes things red is only skin-deep.” We won’t know which is the case until Lucy can take a closer look at examples of all three types of objects.
Once in a lifetime opportunity
One mission target of interest is Eurybates, a 40-mile-wide asteroid which is the largest remnant of a collision in the Trojans. “Planets are formed from collisions,” Levison said “So understanding these collisions will tell us about planetary evolution.”
Another target that Levison is personally looking forward to studying is Patroclus, half of an equal mass binary with Menoetius. These two asteroids, both roughly 70 miles wide, orbit around each other. This is an exceedingly rare type of formation among small bodies, with only a handful of equal mass binary asteroids ever discovered. Astronomers think that binary asteroids “could have been some of the earliest objects in the solar system,” and that this rare pair could be a leftover from the first 100 million years of the solar system’s life.
It’s not easy to study Patroclus and Menoetius, because their orbit is at an angle which means it rarely intersects with regions that are easy for a spacecraft to travel to. But the pair are scheduled to be in an accessible region of space when Lucy performs its flyby of them in 2033.
“It is literally a once in a lifetime opportunity,” Levison said.
A schedule that can’t slip
Lucy is set to launch next year, in October 2021. The launch window is only 21 days long, and if the launch can’t go ahead in this period, it will have to be delayed for an entire year, which would be hugely expensive. The team is taking every precaution it can to avoid that happening.
“That’s the nature of space exploration,” Levison said, “but making the launch window is something we always worry about. At every stage of the process, we emphasize preserving that schedule.” Unlike some larger projects with more flexible timelines, such as NASA’s upcoming James Webb Space Telescope, there’s no wiggle room in the schedule for Lucy: “The date can’t slip.”
To meet the deadline, the team is currently “deep in the manufacturing phase,” Levison said. Having focused on the design of the spacecraft from the approval of the project in 2017 to the preliminary design review in November 2019, the team is now focusing on the fabrication of the craft. Fabrication will take another several months and once completed, the craft will go through testing and launch preparations.
Lucy will launch from Cape Canaveral, Florida, on a small rocket, entering an orbit with a period of one year. Using the gravity of Earth as an assist, the craft will push into the orbit of Jupiter, heading out into the solar system to meet its first target in 2025 and completing its journey to the Trojans between 2028 and 2033.
Bonus asteroid surprise
Once the course Lucy will take between Earth and the Trojans was plotted, the scientists noticed a welcome surprise: It will pass almost right by an asteroid in the main asteroid belt. The scientists decided they would take a stop along the way for a spot of sight-seeing. “After the trajectory was set, we saw it happened to pass by a main belt asteroid,” Levison said. “We were extremely lucky with the planetary alignment.”
The scientists’ luck was in other ways, too. The asteroid Lucy will be passing is a member of the Erigone group, which is one of the youngest asteroid groups in our solar system. As it was formed relatively recently, studying this body may teach us even more about planetary formation, as the scientists can compare the composition of this “pristine” asteroid to other examples of asteroids that have been affected by many more years of exposure to the sun.
In honor of the paleoanthropologist who discovered the original Lucy fossil, the asteroid has been named Donaldjohanson.
You can follow along with the action as the mission prepares for launch on Lucy’s Twitter account.
