Meet Me on Neptune, or Maybe Uranus

It’s tough to believe that it’s been over 50 years since the Voyager 2 left Earth and began its trek into the outer Solar System. It’s almost even crazier to think it takes 50 years to get out to the outer Solar System – goes to show how far away those Gas and Ice Giant Planets are from Earth.

Well, we’ve got some astronomy-awesome news which might come as a big surprise. In case you haven’t been closely following the recent announcements by The Outer Planets Assessment Group (OPAG), a study has begun by the Jet Propulsion Laboratory (JPL) to investigate the possibility of a mission to Neptune or Uranus.

Visiting the Outer Solar System:

You might remember Argo, the last proposed outer Solar System mission, back in 2008, when OPAG was working with Arizona State University to determine the feasibility of visiting the outer Solar System.

Unfortunately, the mission was called off because NASA lacked the funding and quantity of plutonium necessary to propel the spacecraft that far out there.

Despite NASA currently having the funding and available inventories of plutonium for purchase, they’ve missed the critical launch window between the years 2015 and 2020. Even if the mission started back up tomorrow, they wouldn’t be able to make up lost time and wouldn’t benefit from the route needed for gravitational propulsion assist, which this unique window of time provided. Think of gravitational propulsion assist as free energy from sling shot-ing yourself from one planet’s gravitational pull to another.

Where Do Things Stand Today?

Well, NASA will use all of the information from these studies to determine which projects will qualify for future funding, hopefully prioritizing a mission to somewhere in the outer Solar System.

So, let’s say that NASA decides they want to send a spacecraft into the outer Solar System, it’s safe to say that they’re already eyeing a few specific destinations.



Photo by Kevin Gill, https://flic.kr/p/vH1sX1


Neptune’s main moon Triton seems like a very good candidate. The many moons of Uranus are also potential places to visit, along with several other smaller moons which have surface and sub-surface oceans or bodies or water.

Hello Triton:

Triton, Neptune’s largest moon (of Neptune’s 13 moons) is a likely and highly anticipated destination because of its retrograde orbit. This is a peculiar feature that isn’t shared by any other large moon in the entire solar system.

Retrograde Orbit: is when a moon orbits its planet in the opposite direction of its planet’s rotation.

Scientist believe Triton has a retrograde orbit because it was once part of the Kuiper belt, later stolen away and now orbiting Neptune.



“Triton moon mosaic Voyager 2 (large)” by NASA / Jet Propulsion Lab / U.S. Geological Survey – http://goo.gl/QBvCEJ. Licensed under Public Domain via Commons – https://goo.gl/CC2Ejm


Triton is also awesome because its surface is mostly made up of frozen Nitrogen (N), a water-ice crust, an icy mantle with a big ol’ core made of rock and metal.

Triton is also geologically active, which has geysers that erupt Nitrogen into the atmosphere. It’s like the outer Solar System’s version of Old Faithful.

Where Else Might We Go?

Well, others are speculating that the moons of Uranus are plausible candidates.

Uranus has 27 known satellites, but 5 major moons; Miranda, Ariel, Umbriel, Titania and Oberon. Even if you were to add up all the mass of the 5 moons of Uranus, they’d be less than half the mass of Triton (wah wah wah).



“Uranian moon montage” by NASA/JPL – http://goo.gl/oyGWK9. Licensed under Public Domain via Commons – https://goo.gl/dHkvgf


These moons are pretty cool, literally. They’re composed of roughly half ice and half rock. It’s speculated that the ice includes ammonia and carbon dioxide, making these ice-rock conglomerates pretty special.

So What Should We Expect?

Back in 2008, OPAG predicted an outer Solar System visit around or after the year 2040. Thank goodness they were cautiously conservative in their estimates.

Earlier this year, a subcommittee of the House of Representatives pushed for a bill that would have NASA explore an outer Solar System “Ocean World”, which could possibly include: Europa, Enceladus, Ganymede, Triton, Dione, Pluto, and Ceres.

This bill would be to fund a mission to an outer Solar System moon which are thought to have sub-surface oceans and/or other forms of water on their surfaces or sub-surfaces.



Photo by Siyavula Education, https://flic.kr/p/mGcxAh


If this bill is passed and NASA begins this project, we’re very likely to see a mission to the outer Solar System, potentially including Neptune and/or Uranus, very soon. Much sooner than 2040, at least.

Recently, Planetary Sciences Chief Jim Green said during a meeting with the Outer Planets Assessment Group, that the Jet Propulsion Laboratory is drafting up a flagship mission to one or both ice giant planets, Neptune or Uranus.

Sounds like the missions will need to be less than $2 billion, which hopefully will be enough for NASA to get this mission off the ground, pun intended.



Featured Images:
“Uranus as seen by NASA’s Voyager 2” by NASA – http://goo.gl/YtN0vX. Licensed under Public Domain via Commons – https://goo.gl/80bSLc
“Neptune Full” by NASA – JPL image. Licensed under Public Domain via Commons – https://goo.gl/mXxy12

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