Researchers confirmed for the first time that a band of anti-matter particles, called anti-protons, envelop the Earth. The study, published in Astrophysical Journal Letters, confirms theoretical work that predicted the Earth's magnetic field could trap antimatter.

Antimatter is one of the most promising fuels for future space travel. However, there are several technical hurdles to be overcome before an antimatter rocket can be built.

The first is that antimatter does not exist in significant amounts in nature. We’d have to make the antimatter on Earth to use it as fuel for a spacecraft and that would cost us more energy than we could ever get back from the antimatter fuel.

But with the new finding, some researchers believe that the belt of antimatter could be used as a source for fueling spacecraft, an idea already being explored by NASA's Institute for Advanced Concepts.

When designing a spacecraft, it’s vital to keep it light in weight. So you want a fuel source that gives up a lot of energy, but doesn’t weigh much. Antimatter fuel would be about 10 billion times more efficient than any of the chemical rocket fuels we use today.

When matter and antimatter annihilate each other, all their mass is turned into energy, so even a small amount of antimatter can release an enormous amount of energy. One gram of antimatter, annihilating 1 gram of normal matter, can generate as much energy as 23 Space Shuttle external fuel tanks.

Piergiorgio Picozza from the University of Rome Tor Vergata, Italy, detected the particles using PAMELA, a cosmic-ray detector attached to a Russian satellite. PAMELA was launched in 2006 to study the nature of high-energy particles from the Sun and from beyond our Solar System -- so called "cosmic rays."

The Van Allen radiation belt is a torus of energetic charged particles around the Earth, which is held in place by the Earth's magnetic field. It is believed that most of the particles that form the belt come from solar wind, and other particles by cosmic rays.

The big break came from an area known as the South Atlantic Anomaly (SAA), which is a region of space where the Van Allen Radiation Belts are the closest to our surface. When PAMELA passes through SAA, it finds a thousand times more antiprotons than are supposed to come from normal particle decays or, for that matter, anywhere else.

Between July 2006 and December 2008, PAMELA detected 28 antiprotons trapped in spiraling orbits around the magnetic field lines sprouting from the Earth's South Pole. It doesn't seem to be a big number, but that is about a thousand times more than would be expected under normal circumstances.

"We are talking about of billions of particles," Francesco Cafagna from the University of Bari in Italy told New Scientist.

The band is "the most abundant source of antiprotons near the Earth," said Alessandro Bruno of the University of Bari, a co-author of the work told BBC.