Probing Ganymede’s Atmosphere with HST Lyα Images in Transit of Jupiter

Lorenz Roth, Gregorio Marchesini, Tracy M. Becker, H. Jens Hoeijmakers, Philippa M. Molyneux, Kurt D. Retherford, Joachim Saur, Shane R. Carberry Mogan, Jamey R. Szalay

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We report results from far-ultraviolet observations by the Hubble Space Telescope of Jupiter’s largest moon, Ganymede, transiting across the planet’s dayside hemisphere. Within a targeted campaign on 2021 September 9 two exposures were taken during one transit passage to probe for attenuation of Jupiter's hydrogen Lyα dayglow above the moon limb. The background dayglow is slightly attenuated over an extended region around Ganymede, with stronger attenuation in the second exposure, when Ganymede was near the planet’s center. In the first exposure, when the moon was closer to Jupiter’s limb, the effects from the Ganymede corona are hardly detectable, likely because the Jovian Lyα dayglow is spectrally broader and less intense at this viewing geometry. The obtained vertical H column densities of around (1-2) × 1012 cm−2 are consistent with previous results. Constraining angular variability around Ganymede’s disk, we derive an upper limit on a local H2O column density of (2-3) × 1016 cm−2, such as could arise from outgassing plumes in regions near the observed moon limb.

Original languageEnglish (US)
Article number12
JournalPlanetary Science Journal
Issue number1
StatePublished - Jan 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


Dive into the research topics of 'Probing Ganymede’s Atmosphere with HST Lyα Images in Transit of Jupiter'. Together they form a unique fingerprint.

Cite this