A Fresh Glimpse Of Uranus Shows It Has A Swirling Polar Vortex

Scientists at NASA's Jet Propulsion Laboratory have been researching data gathered by the Very Large Array and have developed the new findings. The scientists discovered that the air moving around the North Pole is likely to be warmer and dryer - a definite indicator of a major storm - by analyzing radio waves released by Uranus.

With the exception of Mercury, which has no significant atmosphere, cyclones (or anti-cyclones, which revolve in the opposite direction to the planet's orbit) have now been observed near the poles of every planet in our Solar System.

The Very Large Array, a grouping of 28 radio telescopes situated in the arid desert of New Mexico, which is able to see past the clouds of the ice giant and examine what's going on below, allowed for the observation.

Additionally, modern astronomers who are based on Earth are in a fortunate situation since Uranus is well visible from where it is now orbiting. Uranus spends the last several decades in a position when its poles were not directed toward Earth. Uranus completes its orbit around the Sun in around 84 Earth years. However, the ice behemoth has been ideally positioned for scientists to obtain an excellent view since about 2015.

"These findings provide us a lot more information about Uranus's history. It's a lot more dynamic than you might imagine, according to main research author Alex Akins of NASA's Jet Propulsion Laboratory in Southern California. It's not simply a simple blue ball of gas, though. There is a lot going on underneath the hood.

In 1986, as the Voyager-2 spacecraft flew by Uranus, it saw a number of amazing occurrences, including a whirling pattern that seemed to be the planet's methane clouds spinning at its south pole.

While this looked to be clear evidence of a polar cyclone, Voyager infrared scans revealed no temperature changes, indicating it was something else. However, recent study suggests that Voyager may have witnessed a polar cyclone decades ago. Something far weirder might be going on.

"Does the warm core we observed represent the same high-speed circulation as seen by Voyager?" Akins went on to say. "Or do stacked cyclones exist in Uranus' atmosphere?" The fact that we're still learning such basic facts about Uranus' atmosphere makes me want to learn more about this enigmatic planet." The findings have been published in the journal Geophysical Research Letters.

Uranus' obliquity provides unique chances for polar observation, which can help us better understand polar circulation dynamics on big planets. Our present knowledge of Uranus' polar circulation (we define the pole as being more than 60° latitude) shows that net subsidence is the defining feature of vertical motion. This pattern is deduced from emission and reflection contrasts in multi-wavelength data (de Pater et al., 1989, 1991; Hofstadter & Butler, 2003; Roman et al., 2020; Sromovsky et al., 2019), which show absorbing gas depletion near the poles down to tens of bars.

The most recent updates to the polar zonal wind profiles, which are ostensibly calculated at 1.5 bar, were made by Karkoschka (2015) in southern latitudes using Voyager 2 photos and Sromovsky et al. (2015) at northern latitudes using Keck data. There appears to be substantial asymmetry in the northern and southern pole zonal wind profiles, with mean zonal wind speeds decrementing monotonically from a high of 250 m/s at 60° to near-zero at 90° (Karkoschka, 1998; Sromovsky & Fry, 2005; Sromovsky et al., 2015). Due to this asymmetry and analysis of Voyager gravity data, it is believed that upper tropospheric zonal wind speeds are vertically limited worldwide and should decrease with altitude. For a recent study, see Fletcher et al. (2020).

New characteristics have appeared in photos of Uranus that further confuse this bigger picture as new observations and analytic techniques stretch the limits of spatial resolution and sensitivity. Complex polar phenomena, such as a plethora of compact brilliant spots in the northern hemisphere that may be the result of small-scale vertical convection working to counteract net subsidence, have been recorded at the CH4 weather level, for instance (Sromovsky et al., 2012, 2015).