Uranus Bizarre Weather Revealed
October 17, 2012

New Images Show Uranus Like Never Before

[ Watch the Video: What is Uranus? ]

Lee Rannals for redOrbit.com - Your Universe Online

Uranus is coming into more focus than ever with a new technique developed by astronomers and applied at the Keck Observatory.

Astronomers reported at the American Astronomical Society's Division for Planetary Sciences meeting that they have taken high-resolution infrared images of Uranus, revealing detail of the planet's bizarre weather.

The latest details of the seventh planet from the Sun provide the best look to date at Uranus' complex and enigmatic weather.

Uranus' deep blue-green atmosphere is thick with hydrogen, helium and methane, according to the latest research.

The astronomers said that winds on the planet blow mainly east to west at speeds of up to 560 miles per hour, despite the small amounts of energy available to drive them.

Uranus' atmosphere is almost equal to Neptune's as the coldest in our solar system with cloud-top temperatures nearing minus 360 degrees Fahrenheit.

Larry Sromovsky, a University of Wisconsin-Madison planetary scientist who led the new study using the Keck II telescope, said that large weather systems behave bizarrely on Uranus.

"Some of these weather systems," Sromovsky said, "stay at fixed latitudes and undergo large variations in activity. Others are seen to drift toward the planet's equator while undergoing great changes in size and shape. Better measures of the wind fields that surround these massive weather systems are the key to unraveling their mysteries."

The team used new infrared techniques to detect smaller, more widely distributed weather features, which helps scientists trace the planet's pattern of winds.

"We're seeing some new things that before were buried in the noise," said Sromovsky, a senior staff scientist at UW-Madison's Space Science and Engineering Center.

AURA's Heidi Hammel, a co-investigator on the new observations and an expert on the atmospheres of the solar system's outer planets, said her first reaction to the images was "wow."

"These images reveal an astonishing amount of complexity in Uranus' atmosphere. We knew the planet was active, but until now much of the activity was masked by noise in our data," Hammel said.

The primary mechanism driving Uranus' weather is the solar energy, because there is no detectable internal energy source, according to the researchers.

"But the Sun is 900 times weaker there than on Earth because it is 30 times further from the Sun, so you don't have the same intensity of solar energy driving the system," Sromovsky said. "Thus the atmosphere of Uranus must operate as a very efficient machine with very little dissipation. Yet the weather variations we see seem to defy that requirement."

He said the new images are the most detailed views of Uranus yet, and that no other telescope could come close to producing these results.

The astronomers used Keck II to capture images that, when combined, increase the signal-to-noise ratio and tease out weather features that are otherwise obscured.

The team was able to obtain exposures of the planet that provide a clear view of Uranus' cloud features in just two nights.

"The main objective was to find a larger number of cloud features by detecting those that were previously too subtle to be seen, so we could better define atmospheric motions," Sromovsky noted.

After analyzing the images, the team found a scalloped band of clouds just south of Uranus' equator, and a swarm of small convective features in the north polar regions of the planet.

"This is a very asymmetric situation," Sromovsky added. "There is certainly something different going on in those two polar regions."

He said that Uranus is changing, and that they do not expect things at the north pole to stay the way they are now.

The scalloped band of clouds near the planet's equator may indicate atmospheric instability of wind shear.

"This is new and we don't fully understand what it means," Sromovsky concluded. "We haven't seen it anywhere else on Uranus."