Another celestial body has been added to NASA's bucket list with the space agency officially asking the US Congress for US$30 million for the first mission aimed at exploring Jupiter’s moon Europa. Part of the FY 2015 NASA Planetary Science budget, it would fund further development of an unmanned probe to study places in the Solar System other than Earth and Mars where life may exist.

Though NASA has made studies of missions to Europa before, these have been conceptual, while the new budget request now asks for double last year's appropriations to fund the build up to an actual mission. Though smaller than the Moon, many scientists believe that Europa has a subsurface ocean beneath its ice crust. Europa's ocean may be twice the volume than of all the seas of Earth, and some scientists believe it to be the most likely place in the Solar System where life may exist – if only on the microbial level.

NASA is interested in learning more about this potential ocean, the composition of the brown areas on the moon's surface, and the geological forces forming the ice crust. In NASA's budget request, the mission was called one of the "two highest priority flagships" along with the Mars Astrobiology Explorer-Cacher.

Possible flyby paths of the Europa Clipper (Image: NASA/JPL-Caltech)

If the Europa mission gets the green light from Congress, NASA says that it will be similar to the conceptual Europa Clipper, which the Jet Propulsion Laboratory (JPL) in Pasadena, California has been working on. This would not be an orbital mission, but one with the probe orbiting Jupiter with occasional visits to Ganymede and Callisto to use their gravity to shift the spacecraft's orbit to send it back to Europa. NASA says that such flybys can achieve 80 percent of the science that an orbiter could for half the cost.

Exact details for the mission have yet to be nailed down, but at this time NASA says that the probe would be solar powered using current technology, and hardened against radiation with the electronics sealed in a shielded vault located between the propellant tanks. Instruments would include radar to penetrate the ice, infrared spectrometer, topographic camera, and an ion and neutral mass spectrometer.

Possible mission objectives of the Europa Clipper (Image: NASA/JPL-Caltech)

If the mission follows the Europa Clipper study, the new probe could fly sometime in the early 2020s with a travel time to Jupiter of six and a half years as it builds up speed using flybys of Venus and Earth. Arriving in orbit around Jupiter with a two-hour main engine burn, It would then execute 45 flybys of Europa over a three-month period, passing at an altitude of 16 to 1,675 miles (25 to 2,700 km). At the end of the nominal and any extended missions, the probe would be targeted at the Jovian moon Ganymede for a controlled impact to avoid biological contamination of Europa in the event of an accidental crash.

If the mission is funded, NASA's next step will be to determine the mission requirements, architecture, planetary protection requirements, identification of risks and their mitigation, cost and schedule estimates, and payload accommodations. In addition, planning would focus on current studies of the plumes discovered jetting from the region of Europa's south pole to determine how these might affect the mission's objectives.

Source: NASA (PDF)

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