In the absence of a time machine, astronomers turn to asteroids, comets, and other primordial bodies to trace the origins of our Solar System.
During an upcoming NASA mission, currently scheduled for an October lift-off, a spacecraft called Lucy will be the first to visit a fleet of primordial bodies trailing behind Jupiter. It will launch on the Atlas V 401 rocket.
These rocky bodies are known as the Trojan asteroids — two swarms of rocky bodies associated with Jupiter’s orbit around the Sun. One group leads ahead of Jupiter, and the other trails behind. The primordial squad formed from the same ancient material that formed the outer planets of the Solar System more than 4 billion years ago — this is why NASA calls them “time capsules.”
NASA wants a closer look, so it's sending Lucy to explore. These asteroids, gravitationally bound to Jupiter, are believed to contain clues necessary for deciphering and illuminating the history of the Solar System and the origin of life on Earth.
During the revolutionary mission, the spacecraft will:
- Map the surface geology of asteroids and determine their relative age
- Map the color and composition of the asteroids, looking for organic materials
- Determine the mass and density of the asteroids
- Look for accompanying satellites and rings
When does the NASA Lucy mission launch?
However, it’s possible it will be sent up any time during the 23-day launch window. Every morning during this period there will be a one-hour opportunity to launch. It will lift off from the Cape Canaveral Space Force Station in Florida.
In July, the spacecraft arrived at Kennedy Space Center and was put in a cleanroom to being its final preparations for launch. On September 28, NASA announced most preparations were completed, including:
- Testing mechanical, electrical, and thermal systems
- Testing the launch sequence with mission operators
- Installing the high-gain antenna, which sends back the highest quality data to Earth
- Filling the fuel tanks aboard the craft with hydrazine and liquid oxygen to ensure it has enough to navigate to target asteroids
The next step is to pack the spacecraft into its launch vehicle fairing, the top part of the launch vehicle that will protect Lucy in its ascent to space. In October, it will be sent to the Vehicle Integration Facility to be placed on an Atlas V rocket.
Just prior to the launch, the craft will be tested again. Though it is largely solar-powered, an electrical “umbrella cord” will feed it enough power for launch sequences.
If all goes as planned, it will lift off from Space Launch Complex 41 at Cape Canaveral Space Force Station. This launchpad has launched several groundbreaking missions, including the Mars-bound Viking landers, both Voyager missions to the outer Solar System, the New Horizons mission to Pluto, and the Curiosity rover.
How can you watch the Lucy mission launch?
Depending on Covid-19 restrictions, it’s also possible people can watch in person from the Kennedy Space Center Visitor Complex.
What is the Lucy mission timeline?
The mission is estimated to take 12 years.
In 2025, Lucy’s first stop will be a small Main Belt asteroid called Donaldjohanson. Donald Johanson is an American paleoanthropologist who co-discovered “Lucy,” the name given to Australopithecus afarensis fossils unearthed in Ethiopia in 1974.
The Lucy mission will need two gravitational assists from Earth to get to the Trojan asteroids.
In an FAQ of the mission, NASA states:
“Lucy will be the first spacecraft to travel out to the distance of Jupiter (actually a bit farther) and return to the vicinity of the Earth, for a final gravity assist that will send it back out to its final Trojan encounters.”
The craft will have two encounters with the Trojans, visiting Trojans behind and in front of Jupiter separately, encountering seven Trojans in total on a tour that will take the craft 12 years to complete.
- The Donaldjohanson encounter will take place in April 2025
- From August 2027 to November 2028, the craft will encounter the “Greek camp” of asteroids that orbit in front of Jupiter, visiting five asteroids of various classifications that will help the mission get a good sampling of these pristine objects
- After swinging back through the inner solar system, the craft will visit the Trojan camp of asteroids, encountering the binary asteroids Patroclus and Menoetius satellite
After this portion of the mission, Lucy will float through space — indefinitely. It will travel between the Trojan asteroids and Earth’s orbit for “at least hundreds of thousands, if not millions of years,” NASA reports.
Why are Trojan asteroids important?
The Trojan asteroids orbit the Sun in two main groups, one that leads ahead of Jupiter and another that follows behind.
The first Trojan asteroid was spotted on February 22, 1906, by German astronomer Max Wolf. Eight months later, another German astronomer, August Kopff, discovered a second asteroid followed by a third discovery in February 1907.
By the year 2017, astronomers had identified more than 4,800 Trojan asteroids accompanying Jupiter in its orbit.
Jupiter’s Trojan asteroids have been stable over the entire age of the Solar System, around 4.5 billion years. As the gas giant planet orbits the Sun, its asteroids either move closer to or further away from Jupiter.
But Jupiter isn’t the only planet with Trojans trailing ahead and behind it: In 1990, an asteroid later named Eureka was discovered around Mars and eight more were found since then.
Since 2001, 24 Trojan asteroids were discovered around Neptune.
Asteroids formed from the leftover material that formed the bodies of the Solar System.
Trojan asteroids have been gravitationally trapped in Jupiter’s orbit since the very formation of the Solar System, so they serve as a time capsule of the planets and the Sun’s early history.
Jupiter’s Trojan asteroids are also in the outer Solar System. Because of this, they can likely inform scientists of how other planets, including Saturn, Uranus, and Neptune, formed.
Studying asteroids can also help scientists understand the origin of life on Earth. Scientists believe that water and other biological material may have made their way to Earth by way of these rocky bodies millions of years ago.
What are the Lucy mission goals?
NASA first selected Lucy in January 2017 as the first mission to explore the Trojan asteroids.
The mission is named after the fossilized human skeleton that was found in 1974. Although the human skeleton’s scientific name is AL 288-1, she was dubbed as Lucy after the Beatles song, “Lucy in the Sky With Diamonds.”
While the fossil Lucy revolutionized what we know about the origin story of humans, the Lucy mission aims to help us piece together a different origin story: one of the entire Solar System.
The spacecraft is over 46 feet long. Most of its body is made up of massive solar panels, each almost 24 feet, that will power the spacecraft through its journey.
Over its 12-year mission, Lucy will study seven of the mysterious Trojans and one asteroid from the asteroid belt, which is located roughly between the orbits of Jupiter and Mars. The mission aims to determine the mass and density of each asteroid and determine their origin material.
Lucy will study the surface composition, physical properties, and geology of the Trojan asteroids at close range.
Lucy: A message to future humans
Because it is expected the Lucy spacecraft will float on for thousands, if not millions, of years, it contains a plaque carrying a message to future humans.
Etched onto the plaque is a diagram of the positions of planets during October 2021.
The messages on it are a range of proverbs, quotes from poets, musings from scientists, and thoughts from activists. The languages included are English, Spanish, Turkish, and Polish.
Statements made by Paul McCartney, John Lennon, George Harrison, Ringo Starr, and Yoko Ono are all there — fitting for a Lucy mission. Starr puts his message most simply:
“Peace and Love.”
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