Europa Clipper Earth flyby
Europa Clipper, the largest planetary spacecraft NASA has built, is set to pass about 3,200 km above Earth at around 20:15 UTC on 3 December 2026, gaining the speed it needs to reach Jupiter. It is the second and last gravity assist after Mars in 2025, with arrival at Jupiter planned for 11 April 2030.
The story
Europa Clipper left Earth on a Falcon Heavy rocket in October 2024, and about two years later it is coming back. It is not coming to land but to pick up speed. The spacecraft flew past Mars on 1 March 2025, and at about 20:15 UTC on 3 December 2026 it passes about 3,200 km above Earth, gaining the last of the speed it needs to reach Jupiter. Trajectory designers call this route, using Mars and then Earth, a Mars-Earth Gravity Assist, or MEGA.
Borrowing speed from a planet's gravity is called a gravity assist, or a swing-by. Seen from the planet, the spacecraft arrives and leaves at the same speed; only its direction bends. But the planet itself is racing around the Sun, so when the same pass is measured against the Sun, the bend has turned into extra speed. Earth gives up that speed, but because Earth is so much heavier than the spacecraft, its own motion slows by an amount far too small to measure.
The detour is needed because the spacecraft is big and heavy. Europa Clipper is the largest planetary spacecraft NASA has built, with long solar panels stretched out on both sides to collect the weak sunlight near Jupiter. Fully fuelled, it weighs about six tonnes. The Falcon Heavy that launched it did not have enough power to send that much mass straight to Jupiter, so the mission borrowed help from two planets and accepted a few extra years of travel in return.
The day of the flyby is also a chance to check the instruments. Earth and the Moon are well known, so pointing instruments at them lets the team compare readings with known answers. Arrival at Jupiter is planned for 11 April 2030. While circling Jupiter, the spacecraft is then set to fly close to Europa 49 times to study its icy shell and the ocean beneath it.
Mission goals
The question Europa Clipper is trying to answer is simple: could the ocean under the ice of Jupiter's moon Europa be a place where life could exist? To answer it, scientists need to know how deep the ocean is, how thick the ice above it is, and whether the water touches rock on the seafloor, where chemical reactions can happen. So the spacecraft carries radar that looks into the ice, a magnetometer that measures magnetic fields, spectrometers that identify what things are made of, and high-resolution cameras.
The magnetometer is especially important. As Jupiter's strong magnetic field sweeps past Europa, any layer inside the moon that carries electricity, such as a salty ocean, creates a small magnetic field of its own in response. By measuring how strong that field is, scientists can work backwards to the depth and saltiness of the ocean. The Galileo spacecraft picked up signs of this signal in the 1990s but could not pin down the exact values.
The Earth flyby is not a science discovery in itself, but it is a critical moment for navigation. If the speed or direction is even slightly off, the error has to be corrected with the spacecraft's own fuel, leaving less for the work at Jupiter. A flyby cannot be repeated once it is over, so the approach is fine-tuned with small engine burns to match a path that was calculated years in advance.
Mission chronology and background
Gravity assists have been a basic tool for exploring distant planets since the 1970s. Mariner 10 used the gravity of Venus to reach Mercury, and Voyager 1 and 2 used a rare line-up of the planets to visit Jupiter, Saturn and beyond one after another. Galileo and Cassini also strung together several flybys to reach their targets. For half a century, careful orbit planning has made up for what rockets alone could not do.
Interest in Europa goes back just as far. In 1979, pictures from Voyager showed Europa's surface as a cracked plain of ice with hardly any craters. Few craters mean the surface has been renewed fairly recently. In the late 1990s the Galileo spacecraft flew past Europa many times and gathered evidence of an ocean under the ice, and that work led to a spacecraft devoted to Europa alone.
The space around Jupiter will be busy in the 2030s. The European Space Agency's JUICE arrives in 2031 and will focus mainly on Ganymede and Callisto, while Europa Clipper focuses on Europa. With two spacecraft studying different icy moons at the same time, scientists will be able to compare directly why moons circling the same planet turned out so differently.
Other milestones of this mission
Where to see it — sky and simulator
This is not an event that can be seen in the sky. The spacecraft is a small object that only reflects sunlight, so even at its closest to Earth it is hard to find with an ordinary telescope. Instead, in the orbit view, choose Europa Clipper as the tracked object and set the clock to early December 2026. The screen then draws the big loop that takes it out near the orbit of Mars and back to Earth.
The thing to notice in the replay is how the orbit changes before and after the Earth flyby. Before reaching Earth, the farthest point of the orbit stays near Mars. After passing Earth, the same orbit opens up widely and reaches all the way out to Jupiter's orbit. Speeding up the replay and watching that one sharp bend shows why a gravity assist is often compared to a slingshot.
Updates on the real flyby come through the mission pages of NASA and the Jet Propulsion Laboratory. The closest approach is currently planned for about 20:15 UTC on 3 December, at a height of about 3,200 km, though both figures can shift a little based on navigation just before arrival. If images of Earth or the Moon taken by the spacecraft are released afterwards, they will be the easiest way for the public to see the flyby.
See this for yourself — open it in the simulator
FAQ
Can the Earth flyby be seen from the ground?
Realistically, no. The spacecraft is a small object shining only by reflected sunlight, so it is very faint, and the timing rarely suits any particular place. Following the path in the orbit replay is the reliable option.
Why not fly straight to Jupiter?
Because of its mass. Europa Clipper is NASA's largest planetary spacecraft, and the Falcon Heavy that launched it could not send it straight to Jupiter. One assist at Mars and one at Earth provide the missing speed, at the cost of a few extra years of travel.
Is a flyby like this risky for Earth?
No. The height and time of the pass are calculated years in advance and refined during the approach. The spacecraft does not enter the atmosphere, and its effect on Earth's motion is far too small to measure.
When does it reach Jupiter?
Arrival is planned for 11 April 2030. Rather than orbiting Europa itself, the spacecraft will loop around Jupiter and pass close to Europa 49 times, a design that limits its time in Jupiter's intense radiation.
Related
- Europa Clipper launch
- Europa Clipper reaches Jupiter
- JUICE arrives at Jupiter
- Europa — object index
- Jupiter — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.