Europa Clipper is a space mission that will try to determine if Europa's subsurface ocean could support life
Built and led by NASA’s Jet Propulsion Laboratory in partnership with Johns Hopkins Applied Physics Laboratory; science instruments from U.S. institutions and universities
Launching as early as 2023; arriving as early as 2028
The story thus far
When Galileo Galilei pointed his makeshift telescope towards Jupiter in the early 1600s, he was astonished to see 4 points of light alongside the giant planet. He soon figured out they weren't fixed stars, but “stars wandering around Jupiter like Venus and Mercury around the Sun.” If Jupiter could have satellites, then it was also possible that the Moon could orbit Earth while both, together, orbited the Sun, as Copernicus had argued.
NASA's aptly named Galileo spacecraft visited Jupiter nearly 4 centuries later, orbiting the planet and flying by moons during its 8-year mission from 1995 to 2003. Among Galileo’s discoveries: Europa has a liquid ocean beneath its icy surface. Scientists figured this out in the same way that a metal detector detects keys in your pocket. The detector creates a magnetic field, causing anything conductive to induce another magnetic field that sets off the detector. In Galileo's case, Jupiter supplied the magnetic field, and something deep inside Europa—likely a conductive, saltwater ocean—generated a secondary magnetic field that Galileo detected with its magnetometer. Scientists believe Europa's ocean has more than twice the amount of water as Earth's oceans. Does it also harbor life?
Kevin Hand (JPL/Caltech), Jack Cook (Woods Hole Oceanographic Institution), Howard Perlman (USGS)
Water on Europa vs. Water on Earth
This graphic shows the amount of liquid water on Earth vs. Europa.
Why Europa might have life
Life beyond Earth might be more exotic than anything we can imagine. But here on Earth, life requires a source of energy like sunlight, a liquid solvent like water, and elements like carbon that can easily bond with other elements to form complex organic molecules.
No sunlight reaches Europa's ocean, since the surface is covered with a 20-kilometer-thick ice shell. But there could be other sources of energy, like hydrothermal vents on the ocean floor releasing heat from the moon's core. In the deepest, darkest parts of Earth's oceans, we often find these vents teeming with life—no sunlight required. Another possible source of energy could be metabolism-driving molecules like methane, ammonia, and hydrogen, created by Jupiter's intense radiation bombarding the top of the moon's ice shell.
Hydrothermal vents on ocean floor
In the deepest, darkest parts of Earth's oceans, hyrdothermal vents release heat from the planet's core. These vents are often teeming with life—no sunlight required.
Talking points for space advocates
Europa Clipper will try to determine if Europa's subsurface ocean could support life
The spacecraft will search for signs the ocean has 3 ingredients for life as we know it:
Energy (from hydrothermal vents or metabolism-driving molecules created by Jupiter's radiation)
Light elements like carbon, sulfur, nitrogen, and phosphorus that form complex molecules together
It could launch as early as 2025 and arrive as early as 2028
A Europa mission was The Planetary Society's top advocacy priority from 2013 until the mission was safely funded
Jupiter’s intense radiation means the Europa Clipper spacecraft must be radiation-hardened avoid orbiting Europa directly, while a probe at Saturn would not have those constraints. However, there is enough sunlight at Jupiter for a spacecraft to use solar power, which lowers costs and reduces complexity. Every spacecraft to visit Saturn so far has used nuclear fuel for energy.
Europa Clipper is a huge spacecraft packed with 10 science instruments to scan Europa from above and directly sample the moon's tenuous atmosphere. Its solar panels span 22.3meters, longer than a basketball court.
NASA / JHUAPL
Europa Clipper Science Instruments
Europa Clipper is a huge spacecraft packed with 10 science instruments to scan Europa from above and directly sample the moon's tenuous atmosphere.
Among other things, the instruments will:
Map the ice (REASON) and determine the depth and salinity of the ocean (ECM)
Map the surface in color (EIS) and thermal-image “hot spots” where the ocean may be seeping up through the ice shell (E-THEMIS)
Directly sample Europa's atmosphere (MASPEX, SUDA, PIMS), including possible ocean water, surface particles shot into space by Jupiter's radiation
Jupiter's magnetic field traps high-energy particles from our Sun and speeds them up like a giant particle accelerator, creating a dangerous radiation environment for any spacecraft that dares to fly through it. For this reason, Europa Clipper won't orbit Europa directly. It will stay in a long orbit around Jupiter, occasionally diving through the radiation to collect data from Europa before fleeing the scene. This strategy will allow Europa Clipper to stay at Jupiter for years rather than days or months.
NASA / JHUAPL
Europa Clipper on Basketball Court
Across its solar panels, Europa Clipper measures 22.3 meters (73.2 feet). The spacecraft's central core is 4.6 meters (15.1 feet) high.
If NASA can avoid the Congressional SLS requirement, Europa Clipper could launch as soon as 2023 on a less-expensive commercial rocket like the SpaceX Falcon Heavy or United Launch Alliance Delta IV Heavy. A commercial rocket would force Europa Clipper to rely on gravity assists at Venus and Earth for an extra boost, and it would not arrive until 2030, given a 2023 launch.
Does Europa Clipper include a lander?
No. NASA has proposed a separate lander mission that would spend a month on Europa’s surface, feeding samples into instruments designed to detect organic materials. The mission has not been formally approved. It's possible the Europa Clipper mission will bring CubeSats along to conduct additional science investigations, but those missions have yet to be designed and approved.