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The Interplanetary Superhighway is based around a series of orbital paths predicted by chaos theory, leading to and from the unstable orbits around the Lagrange points — points in space where the gravity between various bodies balances out. There are a number of these around the Earth, created by the balance of forces between the Earth, Moon and Sun. For instance, the L1 point lies at the point between the Earth and Moon where the gravity of the two balances.

Although the forces balance at these points, they are not stable equilibrium points. If a spacecraft placed at the L1 point is given even a slight nudge towards the Moon, for instance, the Moon's gravity will now be greater and the spacecraft will be pulled away from the L1 point. However the entire system is in motion, so the spacecraft will not actually hit the Moon, but travel in a winding path off into space. There is, however, a semi-stable orbit around each of these points. The orbits for two of the points, L4 and L5, are stable, but the orbits for L1 through L3 are stable only on the order of months.

The key to the Interplanetary Superhighway was investigating the exact nature of these winding paths near the points. They were first investigated by Jules-Henri Poincaré in the 1890s, and he noticed that the paths leading to and from any of these points would almost always settle, for a time, on the orbit around it. There are in fact an infinite number of paths taking you to the point and back away from it, and all of them require no energy to reach. When plotted, they form a tube with the orbit around the point at one end.

As it turns out, it is very easy to transit from a path leading to the point to one leading back out. This makes sense, since the orbit is unstable which implies you'll eventually end up on one of the outbound paths after spending no energy at all. However, with careful calculation you can pick which outbound path you want. This turned out to be quite exciting, because many of these paths lead right by some interesting points in space, like MarsMars can refer to different things: Mars is the fourth planet from the Sun. Mars was the god of war in Roman mythology. Mars, Incorporated is a confectioner, and the Mars bar is the name of a candy bar they produce. Mars, the Bringer of War" is a movement. That means that for the cost of getting to the Earth-Sun L2 point (Lagrange points exist for all bodies in orbit of each other, Earth-Moon, Earth-Sun, Mars-Sun etc.) which is rather low, one can travel to a huge number of very interesting points, almost for free.

The transfers are so low-energy that they make travel to almost any point in the solar system possible. On the downside, these transfers are very slow, and only useful for automated probes. Nevertheless, they have already been used to transfer spacecraft out of the Earth-Sun L1 point, a useful point for studying the Sun that was used in a number of recent missions, including the Genesis missionCourtesy NASA/JPL-Caltech) The Genesis spacecraft was the first ever attempt to collect a sample of solar wind, and the first sample return mission to return from beyond the orbit of the Moon. It was launched on August 8, 2001, and crash-landed on Septemb. The Solar and Heliospheric ObservatoryThe Solar and Heliospheric Observatory SOHO is a spacecraft launched in 1995 to study the sun. It is a joint project of the European Space Agency (ESA) and NASA. SOHO Observatory Organization ESA, NASA Wavelength regime optical through UV, also magnetic i is here. The Interplanetary Superhighway is also relevant to understanding solar system dynamics; CometHalley's Comet nucleus sunlit from the left. A comet is a relatively small astronomical object similar to an asteroid but composed largely of ice. In Earth's solar system, the orbits of comets may extend past that of Pluto; of the comets which enter the i Shoemaker-Levy 9Hubble Space Telescope image taken on May 17, 1994. Comet Shoemaker-Levy 9 (formally designated D/1993 F2 was so-named because it was the ninth short-period comet discovered by Carolyn and Eugene M. Shoemaker and David Levy. It was first detected in a pho followed such a trajectory to collide with JupiterJupiter may refer to: Jupiter (god a Roman god Jupiter (planet a planet Jupiter Symphony a symphony by Mozart, (Symphony No. 41 in C major, K. 551) Jupiter, Florida Jupiter IRBM a rocket Jupiter-C a rocket Jupiter, the Bringer of Jollity (or "Joy") a move.