The big ticket items -- the Space Launch System, the Orion capsule, the Commercial Crew program -- grabbed the big bucks and the headlines, as NASA unveiled the White House's 2015 budget proposal. But some astronomers and science fans are most excited about the inclusion of a new mission: a trip to Europa, Jupiter's fourth largest moon.

While the capturing of an asteroid, a return to the moon and a trip to Mars remain the sexiest of NASA's long-term objectives, experts say a robotic mission to Europa could be the most likely to locate extraterrestrial life.

"Looking to the future, we're planning a mission to explore Jupiter's fascinating moon Europa," NASA Administrator Charles Bolden said at an event announcing the new budget on Monday.

"Without a doubt, the new commitment to Europa is the most exciting feature of the President's 2016 budget request for NASA," Casey Dreier, a blogger at The Planetary Society, wrote in the wake of the announcement.

Europa is appealing to astronomers due to the oceans hidden beneath its icy surface. Though the moon is far away from the warmth of the sun, the tidal forces exerted by Jupiter cause friction that warms Europa's innards and keeps its oceans melted and moving. Researchers believe there are likely hydrothermal vents on Europa's ocean floor, and that the moon's icy crust features plate tectonic-like behavior.

While Jupiter's moons are subjected to an overload of radiation, scientists say the Europa's thick surface of ice likely protects the water below (and any potential biosphere) from the ill effects. In fact, the radiation may be responsible for reacting with the icy crust to form nutrients that make life possible. Of course, many of these ideas are simply conjecture (even if they're based on plausible science), but only a more intimate look at Europa's icy world could settle doubts.

"Europa's ocean, to the best of our knowledge, isn't that harsh of an environment," Kevin Hand, deputy chief scientist for the Solar System Exploration division at NASA's Jet Propulsion Laboratory, explained at a media event on Monday -- according to Discovery News.

While fans of a Europa mission are no doubt hoping for a plan to plunge into the moon's oceans, the latest plans involve a flyby mission using a probe concept called the Europa Clipper. The flyby would include several low-flying orbits -- a chance for the Clipper to observe the moon's icy surface and gather data on the oceans below.

"The way we framed the Europa mission science objectives is not to specifically look for life, but to understand habitability; the ingredients for life," Hand said.

Europa missions have been stalled in the research and concept phases for years, but NASA engineers are hopeful that the new funding will make the mission official, and instigate the more specific planning phase -- a phase that would include more details on vehicle design, instrumentation and scientific teams.

"We are really looking forward to next spring when, hopefully, we'll become another flagship mission," Sara Susca, a Europa Clipper payload systems engineer, said.