Next Exit: Europa

NASA's Planning a Mission to Europa

Europa and ocean
Europa may have a hidden ocean beneath its icy crust. We see a cutaway here, against a backdrop of Jupiter and the tiny volcanic moon Io. NASA

Did you know that one of Jupiter's frozen moons — Europa — has a hidden ocean? Data from recent missions suggest that this little world, which is about 3,100 kilometers across, has a sea of salty water underneath its rigid, icy and cracked crust. In addition, some scientists suspect that the jumbled areas of Europa's surface, called "chaos terrain", may be thin ice covering trapped lakes. Data taken by the Hubble Space Telescope also show that water from the hidden ocean is spewing out into space.


How can a small, icy world out in Jovian system contain liquid water? It's a good question. The answer lies in the gravitational interaction between Europa and Jupiter produce what's called a "tidal force". That alternately stretches and squeezes Europa, which produces heating beneath the surface. At some points in its orbit, Europa's subsurface water erupts as geysers, spraying into space and falling back onto the surface. If there is life on that ocean floor, could the geysers bring it to the surface? That would be a mind-boggling thing to consider.

Europa as an Abode for Life?

The existence of a salty ocean and warm conditions under the ice (warmer than surrounding space), suggests that Europa could have areas that are hospitable to life. The moon also contains sulfur compounds and an array of salts and organic compounds on its surface (and presumably underneath), which could be attractive food sources for microbial life.

Conditions in its ocean are likely similar to Earth's ocean deeps, particularly if there are vents similar to our planet's hydrothermal vents (spewing heated water into the depths). 

Exploring Europa

NASA and other space agencies have plans to explore Europa to find evidence for life and/or habitable zones beneath its icy surface.

NASA wants to study Europa as a complete world, including its radiation-heavy environment. Any mission will have to look at it in context of its place at Jupiter, its interaction with the giant planet and its magnetosphere. It must also chart the subsurface ocean, returning data about its chemical composition, temperature zones, and how its water mixes and interacts with deeper ocean currents and the interior. In addition, the mission must study and chart the surface of Europa, understand how its cracked terrain formed (and continues to form),and determine if any places are safe for future human exploration. The mission also will be directed to find any subsurface lakes separate from the deep ocean. As part of that process, scientists will be able to measure in great detail the chemical and physical makeup of the ices, and determine if any surface units could be conducive to life support. 

The first missions to Europa will likely be robotic ones. Either they will be flyby-type missions like Voyager 1 and 2 past Jupiter, Saturn, Uranus and Neptune, or Cassini at Saturn. Or, they could send lander-rovers, similar to the Curiosity and Mars Exploration Rovers on Mars, or the Cassini mission's Huygens probe to Saturn's moon Titan.

Some mission concepts also provide for underwater rovers that could dive under the ice and "swim" Europa's oceans in search of geologic formations and life-bearing habitats.

Could Humans Land on Europa?

Whatever is sent, and whenever they go (probably not for at least a decade), the missions will be the wayfinders—the advance scouts—that will return as much information as possible for mission planners to use as they build up human missions to Europa. For now, robotic missions are much more cost effective, but eventually, humans will go to Europa to find out for themselves just how hospitable to life it is.  Those missions will be carefully planned to protect the explorers from the incredibly strong radiation hazards that exist at Jupiter and envelopes the moons. Once on the surface, Europa-nauts will take samples of the ices, probe the surface, and continue the search for possible life on this tiny, distant world.