  Jupiter, the fascinating largest planet in the solar system, has been visited
by nine spacecraft, which have collected a significant amount of data about
Jovian properties. In this paper, we show that one type of the in situ
measurements on the relativistic electron fluxes could be used to probe dark
matter (DM) and dark mediator between the dark sector and our visible world.
Jupiter, with its immense weight and cool core, could be an ideal capturer for
DM with masses around the GeV scale. The captured DM particles could annihilate
into long-lived dark mediators such as dark photons, which subsequently decay
into electrons and positrons outside Jupiter. The charged particles, trapped by
the Jovian magnetic field, have been measured in Jupiter missions such as the
Galileo probe and the Juno orbiter. We use the data available to set upper
bounds on the cross section of DM scattering off nucleons, $\sigma_{\chi n}$,
for dark mediators with lifetime of order ${\cal O}(0.1-1)$s. The results show
that data from Jupiter missions already probe regions in the parameter space
un- or under-explored by existing DM searches, e.g., constrain $\sigma_{\chi
n}$ of order $(10^{-40} - 10^{-38})$ cm$^2$ for 1 GeV DM dominantly
annihilating into $e^+e^-$ through dark mediators. This study serves as an
example and an initial step to explore the full physics potential of the large
planetary datasets from Jupiter missions. We also outline several other
potential directions related to secondary products of electrons, positron
signals and solar axions.
