NASA's spacecraft has started its journey to an area of the outer Solar System that is yet unexplored: a group of asteroids orbiting Jupiter near the Sun. Vishnu Reddy (a University of Arizona planetary scientist) says that the rocks are the last accessible, but not too well-explored, population of small bodies orbiting the Sun.
The Lucy mission, worth US$981 million, lifted off from Cape Canaveral in Florida on 16 Oct. Scientists believe the Trojans will provide information on the origins and evolution of our Solar System. Their hopes are reflected in the mission name: Lucy, a 3.2 million-year-old hominid fossil discovered in Ethiopia in 1974, is what scientists believe will reveal secrets about human origins.
Audrey Martin, a planetary scientist at Northern Arizona University, Flagstaff who is involved with the Lucy mission, said that Trojans are extremely mysterious.
These asteroids formed around 4.6 billion year ago in the Solar System's outer reaches. This was around when Earth, Jupiter, and other planets began to coalesce from a disk made of gas and dust surrounding the Sun. This scenario would have seen gravitational interactions hurling the Trojans inwards. They now orbit as highly refined examples of the Solar System’s building blocks.
Scientists can examine the Trojans to learn more about the Solar System's primordial, distant parts without needing to send a mission out.
From the outer reaches
A number of missions have explored and explored the main asteroid belt of the Solar System. This is the area between Mars, Jupiter, and Galileo, since 1991 when the Galileo spacecraft passed the asteroid Gaspra. However, no mission has ever been to Jupiters Trojans. These might be quite different from the asteroids in main belt. We learn new things every time we visit new populations," says Cathy Olkin (planetary scientist at Southwest Research Institute in Boulder, Colorado) and Lucys deputy principal researcher.
Near Jupiter, more than 7,000 Trojan asteroids are in two large swarms. These swarms lead and follow the planet's orbit around the Sun. Many other planets, such as Mars and Neptune have Trojan asteroids that closely track their orbits. Earth has at most two. The most well-known Trojans are found on Jupiter.
According to a popular model of planetary formation when the Solar System was formed, the planets were closer to the Sun at the time. Many of them began to migrate due to gravititational interactions. Neptune, Saturn, Uranus, and Neptune moved away from the Sun while Jupiter moved inwards. This chaos saw icy bodies from the Solar Systems outermost reachthe Kuiper Belt, where Pluto, and other small objects orbiting today, get tossed inwards. They were captured by Jupiter and have remained close to each other for billions of year. They are therefore an integral part of understanding the origins and evolution of our Solar System, according to Lori Glaze (director of NASA's planetary-science section at NASA Headquarters in Washington DC).
Rewriting textbooks
Because of their turbulent origins, Trojan asteroids, named after Homer's epic poem, the Iliad, have a wide range of sizes, colours, and shapes. Lucy will visit six of these as part of her quest to understand why they are so different. Eurybates is a 64-kilometre wide remnant of a large cosmic collision and its small moon Queta. It was discovered last year by the Hubble Space Telescope. Other targets include the Leucus, a 20-kilometre-long football-shaped object, and the pair Patroclus, Menoetius and Menoetius. They orbit each other and measure around 100 km in circumference. These binary asteroids can be found in the Kuiper Belt but are not common among Trojans, scientists have confirmed.
Lucy will launch after several loops around Earth in order to get the gravitational boost it needs to reach Eurybates, its first target. It won't reach Eurybates until 2027. The last flyby of Menoetius and Patroclus won't take place until 2033. Olkin states that patience is a must when you're trying to explore outer Solar System.
Lucy, powered by two 7.3-metre-wide solar cells, will speed past each asteroid at six to nine kilometres per second. She will also take measurements such as the colour, composition, and mass of each asteroids. Reddy claims that whatever the mission discovers will almost certainly rewrite textbook entries about the Trojan asteroids. All our formation models might be thrown out the window.
This article was published with permission on October 14, 2021.
