October 12, 2025
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All the Water on Europa
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APOD published October 12, 2025. Credit: JPL/Caltech. A publication-date match, not a photo taken on your date. Independent of NASA.
How much of Jupiter's moon Europa is made of water? No one is sure, but probably a lot. Based on the Galileo probe data acquired during its exploration of the Jovian system from 1995 to 2003, Europa possesses a deep, global ocean of liquid water beneath a layer of surface ice. The subsurface ocean plus ice layer could descend over 100 kilometers in average depth. Adopting a high-end estimate of 100 kilometers depth, if all the water on Europa were gathered into a ball, it would have a radius of over 800 kilometers. To scale, this intriguing illustration compares that hypothetical ball of all the water on Europa to the size of Europa itself (left) - and similarly to all the water on planet Earth. With a volume possibly greater than Earth's oceans, the global subsurface ocean on Europa is a tantalizing destination to search for extraterrestrial life in our Solar System. NASA's robotic Europa Clipper was launched last year to investigate.
Image credit: JPL/Caltech