Europa: Jupiter’s Icy Water-Moon

In the colder, darker outer regions of our Solar System, a quartet of majestic giant planets circle our Sun. Of these gigantic, distant worlds, the banded behemoth, Jupiter, stands out in the crowd as by far the largest planet in our Sun’s family. Jupiter, the “King of Planets”, reigns in splendor from where it is situated beyond the terrestrial planet Mars, and the Main Asteroid Belt that separates the two very different sibling worlds. Jupiter is classified as a gas-giant that may–or may not–contain a small solid core well-hidden beneath its dense and heavy blanket of gas. This gigantic gaseous world is also orbited by an impressive retinue of mostly icy moons, four of which–Io, Europa, Ganymede, and Callisto–were discovered by Galileo in 1610, and were named the Galilean moons in his honor. Of the four moons, small, cracked, icy Europa stands out as a potentially habitable small moon-world, that is thought to have a sloshing, swirling subsurface ocean of life-sustaining liquid water beneath its cracked shell of ice. In November 2019, this possibility was further strengthened because planetary scientists received new evidence that this important ingredient for sustaining life as we know it may sometimes be shot out into space from enormous geysers pock-marking the frozen moon’s mysterious surface. Life as we know it cannot exist without liquid water, and its presence indicates the possibility–though not the promise–that life exists on this distant moon-world.

Four decades ago, a traveling Voyager spacecraft obtained the first up close and personal images of Europa. These pictures revealed brownish cracks tearing through the moon’s icy surface, making Europa look like a jumbo-sized egg with a cracked shell. Missions to the outer Solar System over the past forty years have since collected sufficient additional data about Europa to make it a high-priority target of investigation for NASA scientists searching for life beyond Earth.

What makes Europa so intriguing is the fascinating possibility that it may possess all of the ingredients necessary for the emergence and evolution of life. In November 2019, an international team of astronomers, led by NASA’s Goddard Space Flight Center (GSFC) in Greenbelt, Maryland, announced that they were able to confirm the presence of water in the plumes of Europa’s geysers. They did this by directly measuring the water molecule itself. Up until their study, no one had been able to confirm the presence of water in these plumes by directly measuring the water molecule. The team measured water vapor by studying Europa through the W.M. Keck Observatory in Hawaii, one of the world’s biggest telescopes.

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