A billion miles away, a moon is firehosing ocean water at 800 mph—and it’s loaded with salt, organics, and chemical energy. Enceladus shoots 300‑mile plumes from four 80‑mile “tiger stripes,” even feeding Saturn’s E‑ring; Cassini flew through them 23 times and found molecular hydrogen and silica—classic hydrothermal vent chemistry. Next up: NASA’s Enceladus Orbilander (launch ~2030s, arrive ~2040s) to sniff those plumes for biosignatures—maybe microbes—in a global ocean.