An Atlas V rocket blasted off from Cape Canaveral in Florida on Saturday, carrying a space probe named Lucy, which will study Jupiter’s Trojan asteroids over a 12-year expedition. It’s a first-of-its-kind mission to explore the gas giant’s asteroids.
Mission
Lucy will travel to the outer Solar System, to study asteroids orbiting the Sun near Jupiter. Scientists hope the Trojan rocks will reveal more about how our Solar System formed 4.5 billion years ago.
Trojan asteroids
Trojan rocks are thought to be building blocks of the Solar System and scientists believe these rocks have changed very little since the formation of the Solar System. More than 7,000 Trojan asteroids travel near Jupiter in two large clusters, one ahead of the planet, the other trailing it. One swarm, the ‘Greeks’, moves 60 degrees ahead of Jupiter. The other, the ‘Trojans’, floats 60 degrees behind the planet. The largest known of these asteroids is believed to be 225 km in diameter. The asteroids are named after characters in Homer’s The Iliad.
Why the name Lucy
Lucy is the name given to the 3.2 million years old hominid fossil discovered in 1974 in Ethiopia. Lucy, who belonged to the species Australopithecus afarensis, was discovered by Donald Johanson and his colleagues. What Lucy did to our understanding of human evolution, scientists hope her namesake space probe will do for our Solar System.
The plan
Spacecraft Lucy will fly by six Trojan asteroids. In 2027, Lucy will visit Eurybates and Polymele in the swarm trailing Jupiter. Eurybates has a tiny moon called Queta.
In 2028, Lucy will visit Leucus and Orus, also in the trailing swarm. In 2033, the probe will fly by the Patroclus and Menoetius pair in the swarm leading Jupiter.
Before that, in 2025, Lucy will fly by asteroid Donaldjohanson, named after the discoverer of hominid fossil Lucy. This asteroid doesn’t belong to the Trojan group of rocks.
How the Trojans ended up near Jupiter
One theory is that in the early days of the Solar System, when the planets were forming, the Trojans missed out on becoming Jupiter.
Another theory is that the giant planets Jupiter, Saturn, Uranus and Neptune didn’t occupy their present orbits in the beginning. Scientists believe they were closer to the Sun; later these planets moved away. Many believe the Trojans came from the Kuiper belt.
Juno probe
Ten years ago, NASA launched the Juno spacecraft to Jupiter. The aim was to observe Jupiter’s atmosphere, gravity and magnetic fields. Juno arrived at Jupiter in July 2016. Just a month later, Juno discovered that the planet’s stripes that make it instantly recognisable extend far out into Jupiter’s atmosphere. Juno also captured the first ever inside view of Jupiter’s rings. It also took pictures of the planet’s iconic Great Red Spot.
