NASA launched Europa Clipper from Cape Canaveral, Florida, at 12:06 local time, or 16:06 GMT, sending the spacecraft toward one of Jupiter's most scientifically promising moons. Hurricane Milton had forced the agency to postpone the departure and move the spacecraft indoors before engineers cleared the launch site.
Clipper was scheduled to travel 1.8 billion miles and reach Europa in 2030. It would use the gravity of Mars and Earth to gain momentum because it could not carry enough fuel to propel itself directly to Jupiter. That route would allow it to overtake the European Space Agency's JUICE mission, which launched earlier but was heading onward to Ganymede.
Europa is 628 million kilometres from Earth and slightly larger than Earth's Moon. Its water-ice crust may be as much as 25 kilometres thick, with a large saltwater ocean beneath it that could contain twice as much water as Earth. Salts, sulphur compounds and other chemicals associated with the surface fractures may also provide ingredients relevant to simple life.
The mission was designed to investigate habitability rather than directly promise a discovery of living organisms. Professor Michelle Dougherty of Imperial College London said researchers would look for liquid water, heat and organic material remaining stable over enough time for biological processes to become possible. Better knowledge of the surface could also guide a future landing site.
Earlier observations established the questions Clipper would examine. Scientists identified water ice through telescopes in the 1970s. Voyagers 1 and 2 supplied close images, while NASA's Galileo spacecraft photographed a cracked, reddish-brown surface in 1995. The Hubble Space Telescope later detected possible water plumes rising 100 miles, or 160 kilometres.
Clipper's instruments were expected to map almost the entire moon, collect dust and potentially pass through plumes. A radar instrument called Reason, tested in Antarctica, was designed to probe the ice and help chart structures resembling subduction zones, magma chambers and tectonic features.
Radiation posed a major engineering challenge. The spacecraft was expected to fly past Europa about 50 times, receiving radiation equivalent to one million X-rays during each encounter. Much of its electronics was therefore placed inside a heavily shielded vault.
An international team involving NASA, the Jet Propulsion Laboratory and Johns Hopkins Applied Physics Laboratory would oversee the mission. Once Clipper approached Europa, it would fire its engines to establish the required orbit and begin repeated flybys. The launch started a journey lasting more than five years, with the central scientific goal carefully defined: determine whether Europa's ocean, chemistry and energy sources could create a habitable environment.
