Something’s afoot at Neptune’s South Pole. Back in July 2007, astronomers took a series of infrared pictures of Neptune using the 10 metre W.M. Keck II telescope on Mauna Kea, Hawaii.
Astronomers have long been aware of a bright spot at Neptune’s south pole. The feature first showed up in pictures taken during the Voyager spacecraft flyby and it has been spotted on various occasions since then using ground-based instruments.
So what happened in July 2007 puzzled them: the spot divided into two and then recombined a few days later.
Today, Statia Luszcz-Cook at the University of California Berkeley and a couple of buddies, say they now know what’s going on. The white spots, they say, are probably methane clouds caught in a powerful vortex of winds at the south pole.
The reason they can tell is because a similar phenomena exists at Saturn’s south pole and this has been extensively studied thanks to the marvellous images being sent back by Casini.
Although the hurricane on Neptune isn’t directly visible, Luscz-Cook and co have studied the dynamics of clouds caught in Saturn’s vortex and say the behaviour of the Neptunian clouds is remarkably similar.
These hurricanes have other interesting features. Although their scale is huge–they are thousands of kilometres wide–extraterrestrial hurricanes are remarkably similar to the ones that form on Earth. “The structure of Saturn’s south polar vortex possesses similarities with terrestrial hurricanes, such as a well-formed central eye, concentric eyewalls and a surrounding ring of strong convection,” say the team.
They also point out that the spots on Neptune are “consistent with clouds formed by the upwelling and condensation of methane gas.” Which is another way of saying that it rains methane on Neptune.
The weather on Earth isn’t as unique as we might imagine.
Ref: arxiv.org/abs/1003.3240: Seeing Double at Neptune’s South Pole