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Future space missions may use an interplanetary superhighway to reach their targets in the Solar System NASA have announced. Special points in space known as the Lagrange points are the key to the superhighway through space. These points are where the gravitational pull of the Sun and planet on a spacecraft perfectly balance the outwards centripetal force due to its orbit. This allows the spacecraft to remain at a fixed distance from the Sun and the planet without burning any fuel. Each planet has five of these Lagrange points, L4 and L5 are 60 degrees ahead and behind of the planet, L1 is toward the Sun from the planet and L2 is behind. The point known as L3 is actually on the other side of the Sun. Any spacecraft parked at one of these locations that starts to wander will tend to go into orbit about the Lagrange point. Martin Lo, of the NASA Jet Propulsion Laboratory, has calculated routes between the Lagrange points that would cost spacecraft the least fuel. These are like shifting sinuous tubes across space that Lo likes to describe as the interplanetary superhighway since they mark out the best routes to travel and will make it easier and cheaper for spacecraft to complete their missions.
The Earth's Lagrange points are being used by NASA as 'bases' for a number of spacecraft. The NASA Genesis and the ESA/NASA SOHO spacecraft are both currently at the Earth's L1 Lagrange point. SOHO is making observation of the Sun but has also discovered nearly 500 new comets. Genesis is in a vertical halo orbit around the L1 point and is collecting samples of the Solar Wind for return to the Earth. Other missions, for example, the NASA Next Generation Space Telescope may also be located in the Earth's L2 point away from the Sun.
It is not, however, just satellites and spacecraft that are found in the Lagrange points. Asteroids, known as Trojans, form little clusters in the L4 and L5 points ahead of and behind of Jupiter and Mars. Moons in orbit around a planet, including our own, also have Lagrange points and some of Saturn's moons actually have accompanying Trojans orbiting with them. In the future NASA missions may make use of these Lagrange pit stops in the superhighway to travel back and forth through the Solar System.
More info: NASA Genesis Mission
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