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Why Jupiter Is Now the Best Hope for Finding Alien Life
On the Europa Clipper, the oceans of Europa and the possibility of life beyond Earth
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The Earth, Carl Sagan reported in 1993, showed abundant signs of life. Three years earlier the Galileo space probe had detected oxygen in its atmosphere, picked up an odd amount of methane, and spotted strange radio signals emanating from the planet. Life — at least life involving water, sunlight and oxygen — seemed a likely explanation.
Of course, the question was slightly tongue in cheek. We know Earth is inhabited: we are here, after all. But how, Sagan was really asking, could we find out if another world were inhabited? How, simply by looking at it from space, could we tell if an odd set of properties was driven by biology or mere chemistry?
Later, after Galileo had reached and studied Jupiter, researchers turned its attention to the icy moon Europa. They already knew it to be a strange place. Telescopes had noticed how brightly it shined, especially in comparison to the other moons of Jupiter. Voyager, when it had passed by, had seen a surface laced by tangled cracks and surprisingly…
