Hubble Directly Images Possible Plumes on Europa


NASA’s Hubble Space Telescope
has directly imaged what may be plumes of water vapor on
Jupiter’s icy moon Europa. Europa has long been thought to
harbor a global ocean of water beneath its surface of ice,
making it a prime target of study for anyone interested in
searching for alien life. Eventually our search for life
will take us into that ocean, but until then, the existence of
a water vapor plume would provide an early glimpse into
the ocean’s conditions. In 2012, a team of astronomers used the
Hubble Space Telescope to observe a faint aurora from the
interaction of Europa and Jupiter’s magnetic field. They
detected emissions in wavelengths characteristic of
the breakup of water molecules, and after considering a wide
variety of causes, the team concluded that the most
plausible explanation for these spectroscopic measurements was
the existence of plumes of water vapor erupting from the surface
of Europa. Now a different team of astronomers has used a
different method with similar results – they used Hubble to
image Europa in ultraviolet light as the moon transited
across the disk of Jupiter and were actually able to take
direct images of what appear to be the silhouettes of plumes
rising about 125 miles above the surface of Europa. If these
observations are indeed of water vapor plumes, then they
approximately match the 2012 observation estimates for the
plumes’ mass, height, and location. Also, these plumes are
transient, meaning they come and they go – out of ten
observations of Europa transiting across Jupiter, the
team saw possible plumes on just three of the transits. Both the
recent observations and the 2012 observations provide evidence,
not proof, of water vapor plumes on Europa. Science is a process;
it’s not always cut-and-dried. But future observations by
Hubble, and infrared observations by the James Webb
Space Telescope, could continue to build a case for the
existence of these plumes on Europa. And then NASA’s future
Europa flyby mission would continue the search for the
plumes and visit them to look for evidence of a habitable
underwater world. [music ends]