NASA's Europa Clipper Leverages Mars for Critical Gravity Assist

NASA's Europa Clipper Leverages Mars for Critical Gravity Assist
by Clarence Oxford
Los Angeles CA (SPX) Feb 26, 2025

On March 1, NASA's Europa Clipper will execute a close flyby of Mars, passing just 550 miles (884 kilometers) above the planet's surface. This maneuver, known as a gravity assist, will adjust the spacecraft's trajectory and prepare it for a crucial stage in its journey toward Jupiter's icy moon, Europa. In addition to refining its path, the flyby presents an opportunity for mission scientists to test the spacecraft's radar and thermal imaging instruments.

At its closest approach to Mars at 12:57 p.m. EST, Europa Clipper will be moving at approximately 15.2 miles per second (24.5 kilometers per second) relative to the Sun. The gravity of Mars will gradually alter the spacecraft's trajectory over a span of 24 hours, effectively slowing it down and reshaping its solar orbit. After the encounter, Europa Clipper will depart at around 14 miles per second (22.5 kilometers per second).

This flyby is a key milestone, setting up the spacecraft for its next gravity assist with Earth in December 2026. That maneuver will provide an additional velocity boost, sending Europa Clipper on a direct course toward Jupiter, where it is expected to arrive in April 2030.

"We come in very fast, and the gravity from Mars acts on the spacecraft to bend its path," explained Brett Smith, a mission systems engineer at NASA's Jet Propulsion Laboratory (JPL) in Southern California. "Meanwhile, we're exchanging a small amount of energy with the planet, so we leave on a path that will bring us back past Earth."

Utilizing Gravity for Efficiency

Europa Clipper launched aboard a SpaceX Falcon Heavy from Kennedy Space Center in Florida on October 14, 2024. The spacecraft is undertaking a 1.8-billion-mile (2.9-billion-kilometer) journey to Jupiter, located five times farther from the Sun than Earth. Without the planned gravity assists from Mars and Earth, the mission would either require significantly more propellant-adding weight and cost-or take a much longer route to its destination.

NASA has long relied on gravity assists to optimize space missions. The Voyager 1 and Voyager 2 spacecraft, launched in 1977, used a rare planetary alignment to slingshot past multiple gas giants, capturing unprecedented data along the way. JPL engineers, who oversee Europa Clipper and the Voyager missions, carefully calculate planetary positions and spacecraft trajectories to maximize efficiency.

"It's like a game of billiards around the solar system, flying by a couple of planets at just the right angle and timing to build up the energy we need to get to Jupiter and Europa," said Ben Bradley, Europa Clipper mission planner at JPL. "Everything has to line up-the geometry of the solar system has to be just right to pull it off."

Fine-Tuning the Flight Path

Mission planners initially sent Europa Clipper on a course with a margin of safety around Mars, allowing time for adjustments if needed. Using a series of trajectory correction maneuvers (TCMs), engineers gradually fine-tuned its path for optimal alignment with Mars' gravitational influence.

Three TCMs have already been executed-in early November, late January, and on February 14-to refine the spacecraft's trajectory. Following the Mars flyby, another TCM will take place roughly 15 days later to ensure the spacecraft remains on course. Throughout the mission, controllers may conduct as many as 200 TCMs to maintain accuracy and efficiency as Europa Clipper travels toward its final destination.

Scientific Opportunity at Mars

Beyond navigation, the Mars flyby provides an opportunity to test key scientific instruments aboard Europa Clipper. Approximately one day before the closest approach, the spacecraft's thermal imager will be calibrated, capturing a multicolored image of Mars. The processed data is expected to be returned in the months following the encounter.

Near closest approach, the mission team will also conduct the first full test of the spacecraft's radar system. The radar's large antennas and long wavelengths made ground-based testing before launch impractical, making this flyby a valuable opportunity to verify their operation in space.