Europa Clipper swings by Mars on its Long Journey to Jupiter

Yesterday, Europa Clipper carried out a gravity assist maneuver around Mars, letting the NASA Europa Clipper probe change its trajectory on its way to Jupiter. The closest approach to Mars, the first planetary encounter of Europa Clipper since leaving Earth in October 2024, happened at approximately 17:57 UTC.

Hello Mars! We're now skimming just 550 miles (884 km) above the surface at about 15.2 miles per second (24.5 kilometers per second). pic.twitter.com/pG67qltnrl
— NASA Europa Clipper (@EuropaClipper) March 1, 2025

The probe reached a minimum distance of 884 kilometers (550 miles) from the Red Planet’s surface and is still taking advantage of the planet’s gravitational pull to change its trajectory.

This Martian gravity assist was preceded by three Trajectory Correction Maneuvers (TCM) to bring the spacecraft closer to the Red Planet, and enhance its effect on the trajectory adjustment.

Europa Clipper's first leg of its long journey to Europa. Orbits of Earth, Mars and Jupiter with a blue streak indicating the Europa Clipper trajectory from launch to arrival at Jupiter in 2030 — *The course Europa Clipper is taking to reach Jupiter. Credits: NASA/JPL-Caltech*

The spacecraft will now travel for more than a year, until December 2026, when the final push to reach the Jovian system will occur, thanks to another slingshot gravity assist with Earth. Then, the probe will travel for three more years until its orbital insertion around Jupiter in April 2030.

Testing E-THEMIS for Europa ice

This planetary encounter was chosen to act as a first “testing ground” for some of Europa Clipper’s extremely valuable scientific instruments. In particular, of the 9 instruments being carried by the JPL probe, one is the E-THEMIS thermal imaging system.

The Focal Plane module for the E-THEMIS instrument on Europa Clipper. Two views from front and back, with wiring and electronic components visible — *Focal plane module for the E-THEMIS instrument. Credits: NASA*

The sensor of E-THEMIS was activated one day prior to the closest approach and collected images while coasting Mars, helping teams on Earth to assess the instrument’s operation status and capabilities. This instrument will be fundamental in studying Europa’s ice surface by measuring the temperatures and cooling rates as it is exposed to the Sun’s radiations.

We could soon know whether Jupiter's moon Europa has a liquid ocean beneath its icy crust. Credit: NASA/JPL-Caltech — *The hypothesized liquid ocean beneath Europa’s icy crust. Credits: NASA/JPL-Caltech*

The collected data will help identify thicker ice sheets from more fragmented ones. Also, warmer ice could indicate that the liquid water ocean is potentially closer to the surface. E-THEMIS results could also help find some suitable areas for a future surface mission to Europa.

A baptism of fire for the REASON Radio Instrument

During the Mars flyby, Europa Clipper also tested REASON. The Radar for Europa Assessment and Sounding: Ocean to Near-surface instrument will help investigate deeper parts of the moon, up to 30 km in depth. The antennas will emit high-frequency and very high-frequency waves toward the surface, interpreting the returning signal differences as variations in material properties. The radio waves will be combined to create virtual images.

Europa Clipper in a render doing the mars flyby on March 1 2025 — *Europa Clipper in a render during the Mars flyby. Credits: NASA/JPL-Caltech*

Consisting of various antennas, this large ice-penetrating radar couldn’t be tested on Earth before launch as a full, complete system. This was due to the size of the antennas themselves, which had been stowed for launch, and the nature of the used radio waves, which would have been too large and disrupted by interference to be reliably picked up on Earth.

While Europa Clipper now prepares for another lonely year of travel before getting close to another planet again, we can be assured that the discoveries it will enable will revolutionize how we see Europa and our understanding of its environment and its role in the Solar System.