Pressures of all kinds affect the periodic effects we see in our sky. Stars pulsate, galaxies echo, and even small moons can erupt when their internal pressure gets too great. We know from clear images of the moon Enceladus, taken by the Cassini mission, that this tidally tortured moon erupts organic-rich geysers into space.

The question has been, do we have inarguable evidence to prove the same is happening at Jupiter’s moon Europa. There have been hints in Hubble images, and data from Galileo that can be interpreted as eruptions but… nothing definite. And we still don’t have anything I’d label definitive, but we do have one more computer model saying, yeah, there must be geysers. Looking at data from Galileo’s Energetic Particles Detector from the spacecraft during the same time period when other instruments detected behavior consistent with a geyser, a new team led by Hans Huybrighs found fewer photons then expected, and the only way they can explain this with their models is if they include a geyser. These teams are in many ways trying to say, “Yes there is a Geyser,” by looking at a shadow in the data. So far, nothing else fits the gap we’re seeing. When it someday makes its way toward Jupiter, the Europa Clipper will be able to provide a final answer on geysers or not. Until then, Juno doesn’t have the right setup, so we’re left with local detectors or data, and models to try and figure out what is going on. This work appears in Geophysical Research Letters.

More Information

• Max Planck Institute for Solar System Research article
• “An Active Plume Eruption on Europa During Galileo Flyby E26 as Indicated by Energetic Proton Depletions,” H. L. F. Huybrighs et al., 2020 April 29, Geophysical Research Letters