NASA
True (left) and false-color images of Uranus as taken by Voyager 2 on Jan. 27, 1986. The false color image shows the structure of the planet's atmosphere around Uranus' polar region.
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updated 1/25/2011 3:25:14 PM ET 2011-01-25T20:25:14

Twenty-five years ago, NASA's Voyager 2 zipped past the planet Uranus on its way to Neptune. It was the first spacecraft ever to grab a close-up look at this bizarre world. Voyager 2 made its closest approach on Jan. 24, 1986, and since then we've only been able to gaze on the "ice giant" from afar.

However, Uranus might not be alone for too much longer if a group of 168 scientists from Europe and the U.S. have their way.

In a proposal submitted to the European Space Agency (ESA), a mission called Uranus Pathfinder has been short-listed to make the trek to the outer solar system, arrive in Uranian orbit and study the planet's unique chemistry, rings and its moons and investigate some of the planet's most enduring mysteries. This, in turn, will aid our knowledge of solar system history and how other star systems may form.

Chris Arridge, postdoctoral research fellow of University College London's Mullard Space Science Laboratory (MSSL) and project lead, told Discovery News that the motivation behind Uranus Pathfinder mission is to investigate a giant outer solar system planet that we know little about.

"To have a complete understanding of our solar system we must study all of its components," said Arridge. "It's like having a huge jigsaw and only having half the pieces — we need to get all those pieces to have a chance of being able to see the big picture."

Oddball Uranus
Uranus and Neptune are very different from their other gas giant cousins. Their thick clouds of atmospheric gases contain water, methane and ammonia, plus trace amounts of hydrocarbons. It is for this reason that Uranus and Neptune are often dubbed "ice giants" as they contain significant quantities of ices in their atmospheres. (In contrast, Jupiter and Saturn are composed mainly of hydrogen and helium.)

Whereas the Jovian and Saturnian systems have been studied in-depth by the Galileo and Cassini Equinox missions, the outer ice giants remain a mystery. And things don't get much more mysterious (and down-right bizarre) than oddball Uranus.

One of the most striking things about Uranus is the fact that it orbits the sun virtually on its side. The planet literally "rolls" around the solar system. During its 84-year orbit, each pole spends 42 years facing the sun and then 42 years in perpetual winter. Uranus' weather is driven by these extreme seasons.

"This strange polar orientation suggested that Uranus had been struck by a massive collision early in the history of the solar system," John Cooper, of NASA's Goddard Space Flight Center and Uranus Pathfinder scientist, told Discovery News. Cooper was part of the Voyager 2 team during the 1986 Uranus flyby.

But it doesn't stop there, not only does Uranus' axis of rotation have an extreme tilt, its magnetic poles are out of kilter too.

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"Without a doubt the biggest surprise to me of the Voyager 2 encounter was the discovery that the magnetic poles of Uranus were tilted at 60 degrees to the rotational poles," said Cooper. "On Earth, this would be like having the magnetic north pole in Houston, Texas, instead of in the Canadian Arctic."

Christopher Russell, head of UCLA's Space Physics Center in the Institute of Geophysics and Planetary Physics, agrees that one of the biggest surprises to come from the Voyager 2 flyby was the nature of the planet's magnetic field.

"Uranus' magnetic field seems in some senses more like the solar (magnetic) field — generated in an outer layer and not deep in the interior," Russell said. "Uranian studies may lead to greater understanding of the solar magnetic field."

Moons and rings
Perhaps the magnetic field similarities between Uranus and the sun are a result of a set of common processes working in both solar system bodies, Russell speculates. The only way this can be tested is if a mission, like Uranus Pathfinder, is sent to the planet to study it up close.

In addition to Uranus' weird tilt, there's the question as to why the planet generates little heat. The gas giants are known to emit some heat from processes deep within their atmospheres, but Uranus, once again, is different.

Uranus Pathfinder could find answers to these oddities deep inside planet, but there's a huge wealth of science to be gleaned from the planet's 27 moons, 10 of which were discovered by Voyager 2. For example, do the Uranian satellites interact with the planet in a similar fashion to the moons of Saturn? Is there a radiation belt trapped inside the Uranian magnetosphere, like the Van Allen Belts surrounding Earth?

"I have published a theory that radiation belt particles at Saturn may provide chemical energy to drive the ice volcanoes of the Saturn moon Enceladus, and I wonder if there might also be such volcanoes from similar moon irradiation processes at Uranus," Cooper said.

Uranian logistics
If Uranus could reveal so much, providing us with a huge piece of the solar system puzzle, why haven't we already sent a probe?

Mark Hofstadter, planetary scientist at NASA's Jet Propulsion Laboratory and U.S.-lead investigator for Uranus Pathfinder, points out that before now the logistics of such a mission have been seen as too expensive when considering the science that can be gathered.

"Being farther away makes it more difficult (read more expensive) to get there than to, say, Jupiter or Saturn," Hofstadter said. It's for this reason that missions to the inner gas giants have been preferred. But, in light of technological advancements, the cost of sending a robotic mission to Uranus now is more manageable.

"This is due to past missions answering some questions at Jupiter and Saturn, but just as importantly, recent research — both theoretical and observational — has made us appreciate that the Ice Giants are very important if we are to understand the formation and evolution of planets both in our solar system as well as around other stars," he said.

A Solar System Gold Mine
As Uranus is 1.8 billion miles from the sun — or 19 times the distance from the Earth to the sun — solar panels would be useless to power the Uranus Pathfinder spacecraft, so like the Cassini Equinox mission currently orbiting Saturn, it would need a nuclear power source.

Also, like Voyager 2 that came before it, the mission would most likely use a series of gravitational assists (or "sling shots") by other planets in the solar system to propel Uranus Pathfinder to the outer solar system. Depending on the size of the spacecraft, the mission could take anywhere between 8 to 15 years to reach its destination, says Hofstadter. The team hopes to see Uranus Pathfinder launch in 2021.

"The only way to see how the solar system works in different places is to go there, or for a planet this far away, send an unmanned probe," Arridge concludes. "Uranus sits in quite a different position in the solar system, it's far from the sun, it doesn't appear to give off much heat, it orbits the sun on its side, it appears to have a very different magnetic field and its ring system is unique."

"Uranus is a gold mine to help us understand the planets."

© 2012 Discovery Channel

Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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