March 9 - Alien Weather

Our speaker this week was Statia Cook, a Columbia Teaching Fellow and a Research Associate at the American Museum of Natural History. She is an observational astrophysicist whose research focuses on studies of the weather and climate of other planets, especially the giant planets in the outer Solar System.

Statia started by orienting us to some of the key differences between weather on the Earth and on the "gas giants" (Jupiter and Saturn) and "ice giants" (Uranus and Neptune). On the Earth, the atmosphere is very thin compared the diameter of the planet -- similar to a few layers of cling wrap on a basketball. The giant planets, by contrast, are mostly (or entirely) atmosphere, although their density and temperatures vary with depth to such a degree that the same gasses may behave differently at different layers. In addition, the Earth's weather is driven almost entirely by energy from the Sun, whereas the giant planets still retain a large amount of heat from their formation. The release of that energy can be as important as the Sun to their climate. Finally, on Earth almost all clouds are water vapor, while the various colors seen in the giant planets trace clouds with different compositions including methane and ammonia.

Next, we heard about perhaps the best know extraterrestrial weather pattern: Jupiter' Great Red Spot, a persistent storm larger than the Earth that has existed for at least 180 and possibly more than 350 years. This vortex is accompanied by many other short-lived systems in Jupiter's atmosphere, with colors varying from white to pink to red. Neptune also had a giant storm, dubbed the Great Dark Spot, although it vanished in the five years between its discovery by the Voyager 2 spacecraft and observations by the Hubble Space Telescope five years later.

Finally, Statia told us about some of her own research which include detailed maps of Neptune using submillimeter radio interferometry, a pair of storms near Neptune's south pole that seemed to circle and merge together, amateur-inspired observations of a new Dark Spot on Neptune, and seasonal climate variation of the Ice Giants.

After the talk, Statia fielded questions, followed by a presentation by yours truly on the history of evidence for dark matter.

-- David Hendel (graduate student)