Astronomers discover asymmetry in water vapor distribution over Europa


Europa is the fourth largest satellite of Jupiter and, according to scientists, one of the most promising bodies in the solar system on which extraterrestrial life could exist. Europa’s surface is covered by a crust of ice, and beneath it is a global water ocean.

In 2013, the Hubble Space Telescope took ultraviolet images of Europa. They showed spectral traces of water. Astronomers believe geysers are the source of water in Europa’s extremely rarefied atmosphere. They are blasted from the subsurface ocean through a multi-kilometer ice crust and eject matter 100 kilometers upward.

The new study, which was published in the journal Geophysical Research Letters, analyzes archived Hubble images taken between 1999 and 2015. Lorenz Roth of Sweden’s Royal Institute of Technology, Space and Plasma Physics used new technology to analyze images that recently detected water vapor over Ganymede. As a result, he was able to find that water near Europa has been present for the entire time interval studied.

The constant presence of water in the images of Europa surprised astronomers, because it can not be explained only by geysers. From the surface of the aforementioned Ganymede ice constantly sublimates, i.e. turns from solid to gaseous state, but Europa is a much colder space body. Unlike dark Ganymede, Europa reflects a lot of sunlight, and its surface temperature does not rise above -160° C during the day. Still, Hubble’s observations indicate that the ice on its surface is sublimating.

But even more surprising was the asymmetry of the water vapor distribution over Europa. According to Hubble’s images, water is present only over the “back” hemisphere. Whereas there is no water over the hemisphere, which the satellite is moving forward in its orbit. Scientists still cannot explain this phenomenon.

New data about geological processes on Europa are important in the light of preparations for the launch of the big-budget U.S. research mission Europa Clipper. It will go to study the satellite of Jupiter in 2024. Also in 2022 is scheduled to launch the European mission to study the satellites of Jupiter JUICE.

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