Hubble spots possible water plumes erupting on Europa

Astronomers at NASA’s Hubble Telescope have once again seen evidence of possible water vapor plume eruptions on Jupiter’s moon Europa. Known as a mostly icy moon, Europa is a target for future water testing for evidence of life beyond Earth with these kinds of observations.


As we know, Jupiter is the fifth planet from the sun in our solar system, and it is also the largest planet. Jupiter actually has 53 confirmed moons (with another 14 possible), of which 4 are considerably larger than the rest. These four are called the Galilean satellites, because it was Galileo Galilei who first observed them through a rudimentary telescope about 400 years ago.

Europa is one of those four, and is actually slightly smaller than the size of Earth’s moon. It orbits Jupiter every 3.5 days and is uniquely “locked by gravity to Jupiter such that the same hemisphere of the moon always faces the planet”.


Jupiter and 3 of its 4 largest moons (Europa, Callisto, and Io – from lower left to upper right)

The clear intrigue surrounding Europa is that it is known to be a very icy moon. And where there is ice, there is water in some form.

Vapor Plumes

NASA started to release some evidence that suggested that plumes of water vapor were erupting off of Europa’s surface in 2013. Since then, scientists have been excited by the prospect of a geologically active moon. Europa is known to have very large oceans – with more water than is found on Earth – underneath the icy layer that acts as the moons surface.


Because of the interaction that Europa has with Jupiter (that it is locked in a specific rotation position in relation to Jupiter), which includes an orbit that is closer to Jupiter on one side and much farther on the other side, scientists believe that there could be some very significant “sloshing” occurring – on an ocean sized scale. This was postulated when it was observed that the plumes of water vapor only appeared when the moon was farthest from Jupiter in orbit.

“The apparent plume variability supports a key prediction that Europa should tidally flex by a significant amount if it has a subsurface ocean…”

– Kurt Retherford, Southwest Research Institute in San Antonio, 2013

The vapor plumes are estimated to rise over 100 miles into the air before falling back to the moon’s surface, and have been located on its frigid south pole. The fact that the water breaks the surface of the ice in the form of vapor is significant in that it provides another option for testing the water below the ice, which would otherwise require drilling through unknown depths of solid frozen ice.

Despite confirmation of the observations by two scientific groups through telescopes, perhaps the only way to truly confirm that these observations are actually water vapor is to do a fly by of Europa.

Accordingly, NASA’s James Webb Space Telescope is launching in 2018 to explore what would be only the second moon in the solar system to have jets of water spewing off of its surface.



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