It's been 26 years since a NASA flyby to Neptune and the agency dropped some big news at the Outer Planets Assessment Group meeting, saying that the Jet Propulsion Laboratory(JPL) will be studying a flagship mission to Neptune or Uranus, or even both.

If the mission is approved, the resulting spacecraft will be following in the footsteps of the Mars2020 and Europa Multiple Flyby missions. According to Jim Green, NASA's Planetary Science Division Director, the proposed mission should not exceed $2 billion. Previous flagship missions include the Voyager, Galileo and Cassini.

A mission had been already proposed for Neptune in the past but Argo was grounded because the agency did not have enough stocks of plutonium to power all the spacecraft it had back then. But now that NASA has enough plutonium stores though, it's too late to meet a special 2015 to 2020 launch window that could've put Argo on Neptune within 10 years as it will be assisted by gravity from Saturn and Jupiter.

According to JPL's Candice Hansen however, NASA's Space Launch System could take away the need for gravity assists and get to Neptune or Uranus faster, hopefully beating the 50-year gap projected by scientists between the last mission to the planet and the next.

Whether or not the missions to Neptune or Uranus (or both!) will be on the table will depend on the decision of planetary scientists in charge of assessing priorities for the next decadal survey, which will also determine which projects receive funding.

Triton, Neptune's moon, is an attractive destination because no other large moon within the solar system features a retrograde orbit. Because of this, astronomers suspect that the moon is actually a captured Kuiper Belt object. Triton is almost as big as the Earth's moon, with smoke plumes arising from ice volcanoes spewing nitrogen frost.

Uranus is also a great candidate because it has five moons, all of which are big enough to be counted as dwarf planets had they orbited the Sun on their own.

Earlier in the year, the House Subcommittee on Commerce, Justice, Science, and Related agencies released a bill directing NASA to create an Ocean World Exploration Program. Unfortunately, this won't do much to ensure the agency has continuous missions to the outer solar system as nothing has been lined up after Cassini, which is set to end in 2017 and Juno, which will conclude in 2018. A flyby spacecraft to Jupiter's Europa will unlikely be ready until the mid-2020s.

Photo: Kevin Gill | Flickr

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