Enlarge Image Antimatter reservoir. A newly discovered belt of antiprotons lies within the innermost portion (pink) of Earth's magnetosphere, the large bubblelike region interior to the blue arc that is controlled by the planet's magnetic field. Credit: Aaron Kaase/NASA/Goddard A newly discovered belt of antimatter circling Earth could be an astronaut's best friend. The belt, which consists of antiprotons trapped by Earth's magnetic field several hundred kilometers above the planet's surface, may ultimately become a key source of fuel for missions venturing beyond the solar system. Researchers analyzing data from the PAMELA (Payload for Antimatter/Matter Exploration and Light-nuclei Astrophysics)...