HOUSTON (NASA PR) — Many scientists theorize stars, planets and the molecules that comprise them are only less than five percent of the mass-energy content of the universe. The rest is dark matter, invisible matter that cannot be directly detected but can be inferred.

The Alpha Magnetic Spectrometer – 02 (AMS-02) has been looking for evidence of this mysterious substance from the vantage point of the International Space Station since 2011. Designed for a three-year mission of sifting through cosmic ray particles, AMS records the number of particles that pass through all its detectors (over 140 billion particles to date), the type of particle and characteristics such as mass, velocity, charge and their direction of travel. The goal is for scientists to track down their sources to help understand dark matter and the origins of the universe.