We present a new search for dark matter (DM) using planetary atmospheres. We point out that annihilating DM in planets can produce ionizing radiation, which can lead to excess production of ionospheric ${\mathrm{H}}_3^{+}$. We apply this search strategy to the night side of Jupiter near the equator. The night side has zero solar irradiation, and low latitudes are sufficiently far from ionizing auroras, leading to a low-background search. We use Cassini data on ionospheric ${\mathrm{H}}_3^{+}$ emission collected three hours either side of Jovian midnight, during its flyby in 2000, and set novel constraints on the DM-nucleon scattering cross section down to about ${10}^{-38}{\mathrm{cm}}^2$. We also highlight that DM atmospheric ionization may be detected in Jovian exoplanets using future high-precision measurements of planetary spectra.

• Received 22 December 2023
• Revised 9 April 2024
• Accepted 16 May 2024

DOI:https://doi.org/10.1103/PhysRevLett.132.261002

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society