The oceans offered humanity’s first passage beyond the boundaries of the known world. Ships brought people to unfamiliar shores on voyages of discovery, often just because they could. Today, the oceans of other worlds are the edges of our unknown. In the next decade, scientists will dispatch an armada of ships to these oceans, in hopes of discovering entirely new forms of life.
In the past few years, planetary scientists have learned that some of the moons around the solar system’s biggest planets are full of water. Europa, one of Jupiter’s moons, is thought to have an ocean of liquid water beneath its icy crust. A few million miles away, Saturn’s satellite Enceladus has a water ocean, too. Its sister moon, Titan, has lakes and oceans made of liquid methane. All these moons also have energy sources and hydrocarbons, long thought to be the ingredients for life. If a spacecraft could somehow sample the water, it might be able to look for signs of something living in it.
Luckily for us, both Europa and Enceladus are spitting their water out into space. Enceladus spews so much water, it’s creating an extra icy ring around Saturn. Europa is ejecting much less, but still enough for scientists to see plumes of water shooting out from its surface with the Hubble Space Telescope. Spacecraft could fly through these plumes and take a tiny sip, tasting for the presence of telltale molecules. Think of scooping up ash from the atmosphere above an erupting volcano. It wouldn’t be easy, but it would be a lot simpler than trying to land a rover, boat, submarine, or some other kind of probe.