On Monday, October 14, the Europa Clipper probe officially began its journey to Europa, one of the main moons of Jupiter, with the goal of gathering information on the possible existence of life within it.
The launch, initially delayed by four days due to Hurricane Milton, experienced only a slight deviation from the planned schedule, considering the five and a half years needed for the probe to reach orbit around Jupiter.
From there, it will take another year for the probe to get close enough to Europa to begin its crucial observation phase. Despite the great distance between Jupiter and Earth – up to seven times that between Earth and Mars – the duration of the Europa Clipper mission will be significantly longer than missions to Mars, which take about six months.
However, the determining factor is not the mass of the probe, which weighs about 3,241 kg, significantly more than the Voyager, which weighed a quarter of that mass and took between 18 and 23 months to reach Jupiter.
In fact, Europa Clipper carries a larger amount of fuel, which would allow it to maintain similar speeds if it followed a direct trajectory. The main reason for the extended journey is related to the chosen trajectory: instead of heading directly to Jupiter, Europa Clipper will use a gravitational assist by first passing by Mars.
This technique, which exploits the planet’s gravitational force to “steal” a small amount of its orbital speed, will allow the probe to accelerate without consuming large amounts of propellant.
Although Mars’ mass is considerable, the loss of speed for the planet is so small that it is imperceptible to current instruments. After the flyby of Mars, Europa Clipper will return to Earth, where it will again use its gravity to further increase its speed and head definitively towards Jupiter.
This indirect path will result in the probe traveling a total of about 2.9 billion kilometers, twenty times the distance between Earth and the Sun, despite the maximum distance between Jupiter and Earth being about 590 million kilometers. Gravitational maneuvers have proven essential in space missions, such as the JUICE probe launched in April 2023 with a similar destination, but on a less powerful launcher like Ariane 5, compared to the Falcon Heavy used for Europa Clipper.
Previous missions like Cassini or Juno have also used this technique to achieve stable orbits around their targets without consuming excessive amounts of fuel, a crucial aspect for long-duration missions with high initial masses. This strategy becomes even more important when planning missions to outer planets like Uranus or Neptune, which have orbital speeds very different from those of Earth.
Direct missions to these planets require even greater amounts of propellant, making them extremely complex and costly to fund, also due to the long time expected to reach them.
Gravitational assist techniques therefore remain fundamental for successful space explorations and to reduce the costs and technical complexities associated with exploring the farthest celestial bodies in the Solar System.
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