NASA announced plans Wednesday to embark on a mammoth 20-year project to send a spacecraft to Jupiter's ice-covered moon Europa as its next flagship mission to search for life elsewhere in the solar system.
The mission, which could cost as much as $3 billion, will be managed by the Jet Propulsion Laboratory in La Canada Flintridge. It will focus on the possibility that in the gigantic ocean thought to be hidden under the moon's thick cover of ice is a habitable zone where rudimentary forms of life could exist.
The probe will launch in 2020 in tandem with another orbiter built by the European Space Agency that will focus on Jupiter's largest moon, Ganymede.
The Europa mission's primary scientific goal will be to produce a global map in preparation for a journey many years in the future that would land on the moon.
Using radar and other devices, the probe will try to verify the thickness of the ice sheet and determine the presence of the ocean covering the 2,000-mile diameter moon.
"Europa is tremendously exciting," said Jim Green, director of the Planetary Sciences Division at NASA. "It may have more water underground than the Earth."
NASA's decision to go to Europa is the culmination of years of debate, involving intense lobbying by scientists, space professionals and enthusiasts who have long been fascinated by the romantic image of watery life forms swimming under the surface ice.
"There is no question that Europa has the attractiveness that there could be an ocean below the ice," said Charles Elachi, director of JPL. "Therefore, there could be life under there."
What makes Europa so important, said Robert Pappalardo, a senior research scientist at JPL, is that "icy satellites are the most common potentially habitable environment in the outer solar system," and therefore could be common throughout the universe.
Understanding how they function, and whether they are indeed a good home for life, is key to answering the "are we alone" question.
NASA's decision came down to a contest between Europa and a return to Saturn's giant moon Titan, which had been visited by the Cassini-Huygens mission in 2005.
That joint mission by NASA and ESA uncovered evidence of vast hydrocarbon lakes and methane rainstorms on the moon.
Life as we understand it could not survive the harsh conditions on Titan, the sixth of Saturn's seven major moons. But scientists think it may serve as a model of the early Earth, before it developed into a livable world.
