Scientists with the Outer Planet Atmospheres Legacy (OPAL) program are studying pictures of Uranus and Neptune sent by the Hubble telescope during the period where these ice giants are closet to Earth. These unique new images give us a weather report from more than a billion miles away. The "changing of the seasons" is a new area of study, as Uranus takes 84 of our years to orbit the sun. This image shows that the normally blue planet is covered in white at its north pole.
The large white cap strewn over the north pole of Uranus is particularly dramatic. The likely cause of this feature has to do with the planet’s unique tilt, which causes sunlight to shine directly onto the north polar regions for an extended period of time during the summer. It’s currently mid-summer at Uranus’ north pole, resulting in the protracted white cap.
“The November 2018 image of Uranus occurs at a time 10 years after the equinox, when the northern hemisphere was just emerging into spring sunlight after spending decades in polar winter,” Leigh Fletcher, an astronomer at the University of Leicester, told Gizmodo. “Back in 2007, there didn’t appear to be anything like this polar cap over the springtime pole. But as time progressed, a reflective band—whitish against Uranus’ blue hues—began to appear encircling the north pole. And now, 10 years on, that band has turned into a thick polar cap of aerosols that’s hiding the deeper polar region from view.”
While we think of white on a planet's pole as ice and snow, this white area is the mist from a vast storm. But it's not the only thing going on. The OPAL program is also analyzing other storms on both Uranus and Neptune, which you can read about at Gizmodo.
(Image credit: NASA, ESA, A. Simon/NASA Goddard Space Flight Center, and M.H. Wong and A. Hsu/University of California, Berkeley)