Abstract
A long-overdue hypothesis on the origin of magnetic field of Jovian planets is presented. It is proposed that rapid parahydrogen↔orthohydrogen exchange catalyzed by aerosol clouds of parahydrogen-rich planetary layers renders hyperpolarized nuclear spin state of orthohydrogen (and potentially other proton-containing compounds). This enhancement of nuclear spin polarization by several orders of magnitude (termed hyperpolarization) significantly enhances otherwise negligible proton magnetization. It is hypothesized that this persistent exchange process produces planetary magnetism on Jovian planets. This hypothesis builds on recent experimental evidence that parahydrogen exchange may indeed produce hyperpolarized orthohydrogen.