The Jupiter satellite Europa is the sixth largest moon in our solar system and has fired the imagination of astrophysicists for years. Enormous fountains of water vapor and fine ice particles shoot about 200 kilometers into space from the surface of this celestial body.
That's spectacular in its own right, but what's most exciting is that there must be a vast ocean of liquid water beneath Europa's ice sheet. And because water is an important prerequisite for life, the researchers speculate that life forms could exist in the interior of Europe.
But with a moon far from the sun, whose surface is even covered with frosty ice, how can there be water under this liquid? The scientists have an answer to this: The powerful gravity of the giant planet Jupiter creates strong tidal friction in the interior of Europa. This generates heat, which can be enough to bring temperatures above the freezing point of water.
The first images showing the fountains of Europa were taken by the Hubble Space Telescope in 2013. Now the NASA research probe "Juno" has flown past Jupiter's moon Europa at a distance of only 352 kilometers. The first photo of the probe has landed on Earth and has been published by Nasa. It shows the moon's icy crust in a region called Annwn on the equator. The pixels of the image recorded with the so-called "JunoCam" are one kilometer in size.
The research probe only had a two-hour window to take photos of Europa's surface as it sped past the moon at a speed of around 24 kilometers per second. But everything seems to have worked as intended.
"It's too early to draw a final conclusion, but everything indicates that Juno's flyby of Europa is a great success," says Scott Bolton of the Southwest Research Institute in San Antonio. "This photo is just a harbinger of the new insights about Europe that Juno will bring to us with its instruments and sensors."
The probe not only obtained optical data on the structure of Europa's ice surface, but also on its composition and the lunar ionosphere, which interacts with Jupiter's magnetic field. "We will compare the images of Juno with previous images of Europa and see if anything on the surface has changed over the past two decades," says Juno researcher Candy Hansen of the Planetary Science Institute in Tucson, Arizona.
In the past, the research probes "Voyager 2" and "Galileo" had images of Europa's surface - albeit with a lower resolution. Thanks to Juno, researchers will now have a much higher resolution surface map of the moon.
Overall, the new information about Europe's geology is an important basis for the "Clipper" mission, which NASA is planning in 2024. This research probe will use a special radar to look through Europa's ice surface and possibly detect liquid water underneath.
With instruments sensitive to magnetic fields and gravity, the sub-icy water resources could be measured more precisely. It will also measure the composition of Europa's thin atmosphere.
If there were life forms in Europe's water world, then telltale molecules could enter the moon's atmosphere with the fountains. If “Clipper” manages to prove this, it would be spectacular. Well, it won't be really exciting for a few years. But these days, Juno is a key enabler for future exploration of Europa, the moon that could harbor life.