Explaining The Universe on Instagram: "Spacecraft can use the gravity of planets or moons to change their velocity and direction through a technique called a gravity assist or gravitational slingshot. This method takes advantage of the motion and gravitational pull of a celestial body to boost or alter a spacecraft’s path without using extra fuel. When a spacecraft flies close to a planet or moon, it is pulled by the body’s gravity, gaining speed as it falls toward it and losing speed as it move