NASA is set to launch a spacecraft called Lucy on a 12-year mission to explore a group of rocky bodies known as the Jupiter Trojan asteroids for the first time, gathering new insights into the formation of the solar system.

The Atlas V rocket responsible for propelling the probe was scheduled to take off at 5.34am local time from Cape Canaveral, Florida, the United States, today.

Named after an ancient fossil of a pre-human ancestor, Lucy will become the first solar-powered spacecraft to venture so far from the Sun and observe more asteroids than any probe before it – eight in all.

Additionally, it will make three Earth flybys for gravity assists, making it the first spacecraft to return to the vicinity of our planet from the outer solar system.

“Each one of those asteroids, each one of those pristine samples, provides a part of the story of the solar system, the story of us,” said Nasa Space Mission associate administrator Thomas Zurbuchen.

Lucy’s first encounter will be with asteroid Donaldjohanson in the Main Belt, between Mars and Jupiter, in 2025. The body is named for the discoverer of the Lucy fossil.

Between 2027 and 2033, it will encounter seven Trojan asteroids – five in the swarm that leads Jupiter, and two in the swarm that trails the gas giant. The largest of them is about 95km in diameter.

Lucy will fly by its target objects within 400km of their surfaces, and use its on-board instruments and large antenna to investigate their geology, including composition, mass, density and volume.

A diamond in the sky

The Jupiter Trojan asteroids, thought to number more than 7,000, are leftover raw materials from the formation of giant planets – Jupiter, Saturn, Uranus and Neptune.

Scientists believe they hold vital clues about the composition and physical conditions in the protoplanetary disk from which all the Sun’s planets, including Earth, formed.

They are broadly grouped into two swarms – the leading swarm is one-sixth a lap ahead of Jupiter, while the trailing swarm is one-sixth behind.

“One of the really surprising things about the Trojans, when we started to study them from the ground, is how different they are from one another, particularly with their colours,” said the mission’s key scientist, Hal Levison.

Some are grey, while others are red – with the differences indicating how far away from the Sun they might have formed before assuming their present trajectory.

Lucy the fossil was discovered in Ethiopia in 1974 and helped shed light on human evolution. The space mission’s name was chosen with the hope that it will shed light on the solar system’s evolution.

The paleoanthropologists who discovered the hominin remains named her after the Beatles song Lucy in the Sky with Diamonds, which they were loudly playing at the expedition camp.

Lucy the probe will be carrying a diamond beam splitter into the sky – the Lucy Thermal Emission Spectrometer, which detects far infrared radiation – to map asteroid surface temperatures.

By measuring the temperature at different times of day, the team can deduce physical properties such as how much dust, sand or rock is present. – AFP, October 16, 2021.