This observing season, three of Jupiter’s many storms – called white ovals – happen to resemble the face of the famous Disney character Mickey Mouse. Two ears and a big nose. Just like Mickey, they might be up to mischief.
Jupiter has lots of these white ovals and brown ones, too. They’re hurricane-like storms in the planet’s atmosphere similar to but smaller than the behemoth Great Red Spot. Most don’t have names unless they’re around a long time or expand and merge with other ovals.
The white variety are swirling vortices of cold ammonia ice clouds high in the upper atmosphere. Astronomers find them at many locations tucked within the planet’s cloud belts. Brown ovals are holes in Jupiter’s cloud deck that let us peer deeper into the warmer atmosphere below. They typically only appear within a few degrees of the 20 degree north latitude zone.
Back in the late 1930s, a bright white band of clouds appeared along Jupiter’s 30 degree south latitude zone and eventually coalesced into three separate counterclockwise spinning ovals named FA, DE and BC.
In the late 1990s the trio gradually met up merged into a single larger oval named ‘BA’ about as wide as the Earth around 2000. Five years later it developed a reddish-orange color, inspiring amateur astronomers to nickname it Red Spot Jr. The feature, now more circular than oval, still cycles around the planet to this day. Its color, like that of the Great Red Spot, is believed to come from the mixing of sulfur, carbon and phosphorus compounds sucked up from the lower atmosphere.
The Great Red Spot (GRS) is one of the biggest storms in the solar system with wind speeds up to 400 mph (650 km/hr). Currently about 1.5 Earths wide, it’s persisted for several centuries. For all we know it too resulted from a long-ago merger.
Coincidentally, you can see it late tonight across the Americas. The Spot sits squarely on the planet’s centerline around 12:30 a.m. CDT March 29 (1:30 a.m. Eastern, 10:30 p.m. Pacific). If that’s too late, you can start looking about 1-1/2 hours before these times when it will be to the east of centerline. Click HERE to find the best times for viewing the storm from your city.
Jupiter’s all weather all the time. Ovals change shape, push each other around and even merge. While you might strain to see white ovals or even Red Jr. in the telescope, make no mistake, these are big storms by earthly standards. Mickey Mouse’s ears are about one-third the width of the GRS or approximately half as big as our planet. I wouldn’t want to get close to that hurricane!