Earth is the blue planet, yet surprisingly dry compared to many other worlds. Only 0.2 percent of the earth’s mass consists of water. Especially moons beyond the orbit of Mars often have a thick crust of ice. These include the Jupiter moons Europa, Ganymede and Callisto, the Saturn moon Enceladus or the Neptune moon Triton. For a long time it was completely unclear what is under the ice.
In this episode, Karl tells how the first ocean outside of Earth was discovered on Europa at Jupiter. Astronomers have known Europe for more than 400 years. Still, it took centuries of scientific advances, many years of observations, and multiple spacecraft to look beneath the ice sheet. Under several kilometers of ice, it might be teeming with life.
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episode picture: NASA/JPL-Caltech/SETI Institute