Washington (AFP)

The first NASA probe sent to the distant Trojan asteroids, located in the orbit of Jupiter, began a 12-year journey on Saturday morning, a mission called Lucy which should allow us to better understand the formation of our solar system.

The Atlas V rocket responsible for propelling the spacecraft took off on Saturday at 5:34 a.m. local time (9:34 a.m. GMT) from Cape Canaveral in Florida.

The craft will be the first solar-powered to venture this far from the Sun, and will observe more asteroids than any before it - eight in all.

Each of these asteroids must "deliver a part of the history of our solar system, of our history," Thomas Zurbuchen, director of the science division of the US space agency, told a pre-launch press conference.

Around 2025, the spacecraft will first fly over an asteroid in the main asteroid belt, located between Mars and Jupiter.

Then, between 2027 and 2033, he will visit seven Trojan asteroids.

The largest of them is about 95 km in diameter.

Nasa's Lucy mission to the asteroids of Jupiter Jonathan WALTER AFP

Lucy will approach the selected objects at a distance of only 400 to 950 kilometers, depending on their size, and at a speed of approximately 24,000 km / h.

Thanks to three scientific instruments on board as well as a large antenna, the researchers want to study their geology, their composition as well as their precise density, mass and volume.

Measurements impossible to do with telescopes from Earth.

"Lucy embodies NASA's ongoing quest to venture further into the cosmos, in the name of exploration and science, to better understand the universe and our place within it," said shortly after the take-off Bill Nelson, the head of the US space agency, in a statement.

The Trojan asteroids, of which about 7,000 are known, evolve around the Sun in two groups, one preceding Jupiter, the other following it.

"One of the surprising things about Trojan asteroids is that they are very different from each other, especially their color: some are gray, some are red," said Hal Levison, senior researcher for this mission.

"We think their color indicates where they're from."

- Diamond in the sky -

Lucy will, during her journey of more than 6 billion kilometers, fly three times over the Earth to take advantage of its gravitational assistance in order to propel herself.

The spacecraft will thus be the first spacecraft to return to the vicinity of the blue planet from the confines of the solar system.

Its two solar panels are huge, each measuring more than seven meters in diameter.

The mission was named Lucy in reference to the Australopithecus fossil discovered in Ethiopia in 1974, which helped shed light on the evolution of humanity - NASA here wishing to shed light on the evolution of the solar system.

The researchers who found this skeleton were listening at the time to the Beatles song "Lucy in the sky with diamonds".

In the blink of an eye, the official logo of the NASA mission was drawn in the shape of a diamond.

“We do take a diamond on board,” smiled at the pre-launch press conference Phil Christensen, responsible for the scientific instrument called L'TES, which contains the gemstone.

This instrument will measure infrared light, which will determine the surface temperature of the asteroids.

"By comparing these night and day measurements, we can determine whether the surface is made of boulders or fine dust and sand," he explained.

Indeed, the rock cools less quickly than the sand at night.

The total cost of the mission, including its 12 years of operations, is $ 981 million.

© 2021 AFP