Jupiter-bound JUICE spacecraft just got an 8,000 mph speed boost from Earth: 'This is great news for science'

A blue white and green sphere next to a silver box with gold wing-like panels — An illustration of the JUICE spacecraft making a flyby of Earth (Image credit: Robert Lea (Created with Canva))

The JUICE (Jupiter Icy Moons Explorer) spacecraft returned to Earth on Monday (Sept. 28), but just for a brief flying visit. The European Space Agency (ESA) probe stopped by only to pick up a gravity assist to continue its voyage to Jupiter and its moons.

JUICE launched in April 2023, and this is the third time during its three and a half year mission that it has picked up a gravity assist. This included performing the first-ever lunar-Earth flyby in August 2024, and grabbing a speed boost and trajectory alteration from the second planet from the sun, Venus, a year later in August 2025.

During the flyby, JUICE came to within 5,370 miles ( 8640 kilometers) of Earth, with careful adjustments made to help the probe avoid colliding with satellites around our planet.

"All flybys are risky, requiring very careful planning and continuous monitoring. But the upcoming Earth flyby is much simpler from an operational perspective than the 2024 lunar-Earth flyby, where a flyby of the moon set Juice up for a flyby of Earth the next day," Claire Vallat, Juice Project Scientist, said in a statement. "This is great news for science, because it means we will be able to turn Juice in all different directions to point its science instruments at different parts of Earth and the moon."

The purpose of this latest JUICE/Earth flyby is to deflect the trajectory of the spacecraft by around 20 degrees while increasing its speed by around 7,830 miles per hour (3.5 kilometers per second).

JUICE was above the Indian Ocean when it made its closest approach to Earth at around 7:45 am EDT (1145 GMT).

A blue and green sphere above a curved yellow line there are white captions below the line and red captions above the line — The path of JUICE around Earth during its Sept. 28 flyby. (Image credit: ESA)

JUICE makes flybys like this because, without them, it would require immense amount of fuel to achieve the speeds necessary to reach Jupiter — and that's not to mention the fuel that would be needed to stop JUICE from shooting right through the Jovian system. Instead, the gravity of Earth, Venus, and the moon has been used to adjust the speed and trajectory of JUICE.

As a result, JUICE will have sufficient fuel left to enter the orbit of Jupiter in 2031 and then hop to an orbit around the Jovian moon of Ganymede three years later in 2034.

In the meantime, JUICE is set to make a third and final flyby of Earth in January 2029.

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.