Astronomie - Astronomers have spotted a new type of storm on Saturn


The tempests are larger than other squalls but smaller than massive Great White Spots


Until now, astronomers have only seen Saturn ravaged by small storms that last days or enormous Great White Spots that last months (a Great White Spot that raged in 2010 and 2011 pictured). Now, astronomers have identified a third, midsize kind of storm activity on the gas giant.

Saturn saw some weird weather last year.

Telescope images have revealed a newfound type of storm activity that raged near Saturn’s North Pole in 2018, researchers report online October 21 in Nature Astronomy.

Until now, astronomers had seen only two kinds of Saturnian storms: relatively small storms about 2,000 kilometers across that appear as bright clouds for a few days and Great White Spots that are 10 times as large and last for months (SN: 4/14/15). The newly spotted weather disturbance was a series of four midsize storms. Each was several thousand kilometers across and lasted between about 1.5 weeks and about seven months.

Saturnian storms are thought to originate in water clouds hundreds of kilometers below the planet’s visible upper cloud cover. Studying such storms can offer a window into deep atmospheric goings-on that aren’t directly observable, says Agustín Sánchez-Lavega, who studies planetary atmospheres at the University of the Basque Country in Bilbao, Spain.

Sánchez-Lavega and colleagues analyzed hundreds of telescope images taken by amateur astronomers, as well as pictures from by the Calar Alto Observatory in Spain and NASA’s Hubble Space Telescope. From late March to late October 2018, four unusual bright spots appeared in Saturn’s atmosphere near the North Pole, between the latitudes of 67° N and 74° N.

Computer simulations indicate that each midsize storm required about 10 times as much energy as a small storm to get going, but only about one-hundredth the energy required to brew up a Great White Spot.

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