On January 24, 1986, NASA’s Voyager 2 spacecraft reached Uranus. It was the first and only time we have ever visited the mysterious gas giant. 30 years ago, Voyager 2 closely studied the planet for 5.5 hours as it soared within 50,600 miles.
“We knew Uranus would be different because it’s tipped on its side, and we expected surprises,” said Ed Stone, project scientist for the Voyager mission. Stone continues in his role as project scientist to this day.
Much like how Pluto is surprising scientists today, Uranus stunned 30 years ago. The up-close study of the planet revealed it to be the coldest planet known in our solar system. Yep, even colder than Neptune. How? Uranus doesn’t have an internal heat source.
Voyager 2’s data told scientists Uranus’ atmosphere is made up of 85% hydrogen and 15% helium.
One of the biggest surprises came from Uranus’ magnetic field. It was unlike anything scientists had seen before. Most planets in our solar system (Mercury, Earth, Jupiter and Saturn) have magnetic fields aligned with their rotational axis.
“Then we got to Uranus and saw that the poles were closer to the equator,” Stone said. “Neptune turned out to be similar. The magnetic field was not quite centered with the center of the planet.”
My favorite Uranus discovery? Miranda. It’s an icy moon with a very weird surface.
Giant canyons stretch across its surface that could be nearly 12 times as deep as the Grand Canyon in Arizona. Check out that massive notch at the bottom. Reminds me of the canyon notch on Pluto’s moon Charon.
One of the most unique features on Miranda are called ‘coronae.’ They are lightly cratered groups of ridges and valleys. The feature is common on Venus and is believed be formed when warm material pushes the crust upwards and then collapses in the middle. In Miranda’s case, the gravitational pull from Uranus is believed to be heating up ice in the moon’s interior.
Today, Voyager 2 is 110.988 AU from Earth, or 16,603,693,100 kilometers. Voyager 2 will fly another 3.3 AU away from Earth every year.
Suzanne Dodd, project manager for Voyager, describes what made Uranus so special. “It was my first planetary encounter and it was of a planet humanity had never seen up close before. Every new image showed more details of Uranus, and it had lots of surprises for the scientists. I hope another spacecraft will be sent to explore Uranus, to explore the planet in more detail, in my lifetime.”
Visiting Uranus again?
NASA is thinking about it. Last year, the space agency began looking into how feasible it would be to get a probe back to Uranus and Neptune. “I’ve asked the Jet Propulsion Laboratory to initiate an ice giant study,” Jim Green, NASA’s director of planetary science, said at a presentation to the Outer Planets Assessment Group.
As with anything NASA does, money is the main sticking point. Any mission would be under a $2 billion cap in 2015 dollars.
What will JPL be looking at? First, the science objectives. What exactly would any probe hope to accomplish? Then, the instruments needed to complete these objectives. This is the exciting part. Technology is much more advanced than it was when Voyager 2 reached Uranus in 1986. Remember, Voyager 2 launched in 1979. It was using tech that wasn’t much older than the Apollo era.
JPL will also be looking at how much a proposed mission will cost. $2 billion is the cap. And finally, nuclear fuel. This is nearly as important as money. NASA has a small supply of nuclear fuel, specifically plutonium-238. Probes need it to power themselves on long journeys. Thankfully, there is some good news on that front. Last month, scientists announced they have produced a powder of plutonium-238 for the first time in almost 30 years.
Did You Know: As plutonium-238 decays into uranium-234, it releases heat. This heat is converted into electricity by NASA’s Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). Perfect for deep-space missions.
Even if the JPL study likes the idea of a Uranus/Neptune mission, we are still a long ways off from seeing it. Any NASA mission to the gas giants wouldn’t launch until the late 2020s or 2030s at the earliest.
After the astounding success of the New Horizons Pluto mission, I can’t wait to see what secrets Uranus (or Neptune) still hold.