NASA’s Galileo spacecraft encountered an active water plume during a flyby of Jupiter’s icy moon Europa in 2000, according to a new study published in the journal Geophysical Research Letters.
Water vapor plumes on Jupiter’s icy moon Europa. Image credit: David Ladd, USRA & NASA’s Goddard Space Flight Center.
Europa appears to be scratched and scored with reddish-brown scars, which rake across the surface in a crisscrossing pattern.
These ‘scars’ are etched into a layer of water ice, which is thought to be at least several kilometers thick and covering a vast subsurface ocean.
The colors visible across the moon’s surface are representative of the surface composition and size of the ice grains: reddish-brown areas contain high proportions of non-ice substances, while blue-white areas are relatively pure.
Planetary scientists are keen to explore beneath Europa’s thick blanket of ice, and they can do so indirectly by hunting for evidence of activity emanating from below.
In the new study, ESA researcher Hans Huybrighs and colleagues analyzed archival data collected by the Galileo Solid-State Imaging (SSI) experiment during Galileo flyby E26 in January 2000.
The scientists aimed to understand why fewer than expected fast-moving protons were recorded in the vicinity of Europa during the flyby.
Researchers initially put this down to Europa obscuring the detector and preventing these usually abundant charged particles from being measured.
However, Dr. Hans and co-authors found that some of this proton depletion was due to a plume of water vapor shooting out into space.
This plume disrupted Europa’s thin, tenuous atmosphere and perturbed the magnetic fields in the region, altering the behavior and prevalence of nearby energetic protons.
“Europa plumes would offer a possible way to access and characterize the contents of its subsurface ocean, which would otherwise be hugely challenging to explore,” the authors said.
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H.L.F. Huybrighs et al. An Active Plume Eruption on Europa during Galileo Flyby E26 as Indicated by Energetic Proton Depletions. Geophysical Research Letters, published online April 29, 2020; doi: 10.1029/2020GL087806
