JEM-EUSO will address basic problems of fundamental physics and high-energy astrophysics studying the nature and origin of the Ultra High Energy Cosmic Rays (E > 3×10¹⁹ eV). 

JEM-EUSO will pioneer the investigation from Space of  UHECR-induced Extensive Air Showers making precise measurements with unprecedented statistical accuracy of the primary energy, arrival direction and composition of UHECRs, using a target volume far greater than it is possible from the ground. Such data will shed light on the origin of the UHECRs, on the sources that are producing them, on the propagation environment from the source to the Earth and, possibly, on the particle physics mechanisms at energies well beyond the ones achievable in man-made accelerators. Moreover, exploratory objectives such as constraining the galactic and extragalactic magnetic fields, the detection of extreme energy neutrinos and gamma rays, the verification of special relativity at extremely large Lorentz factors, the examination of possible quantum gravity effects at extreme energies, and the systematic surveillance of atmospheric phenomena, complete the scenario of the JEM-EUSO science goals.

Astrophysics and Cosmology Main Science Objectives: identification of UHE sources measurement of the energy spectra of individual sources measurement of the trans-GZK spectrum Exploratory objectives: discovery of UHE neutrinos discovery of UHE Gamma-rays study of the galactic and local extragalactic magnetic field Atmospheric Science nightglow the transient luminous events (TLE) meteors and meteoroids A new window on the unknown particle Physics: String Theory relativity and quantum gravity effect