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Charting Massive Winds On Gas Giants Of The Outer Solar System

May 17, 2013
Image Caption: Image from the Voyager II flyby of Neptune in August 1989. Credit: NASA

John P. Millis, Ph.D. for redOrbit.com – Your Universe Online

Predicting the weather is difficult. With varying pressures, planetary rotation and various other factors, weather systems on Earth border on chaos. But, believe it or not, predicting the weather on the third rock from the sun is rather straightforward compared to predicting the atmospheric motions of the gas giants that lay beyond the asteroid belt.

The primary reason is that, unlike Earth, the Jovian worlds do not have solid surfaces, rather they are layer upon layer of fluid gas and semi-liquid, all suspended above an Earth sized metallic core. Deciphering the true atmospheric motions above the “surface” layer, wherever that may be, is non-trivial.

Modeling the cloud patterns, and understanding what motivates them, is dependent on what lies below the atmosphere. Are interactions near the core percolating to the surface, driving the observed motion? Or could the wind systems be intrinsically tied to processes just below the surface?

Now, new research is placing limits on the atmospheric motions of the outer most planets in our solar system: Uranus and Neptune. It turns out, to begin understanding the underlying structure and dynamics of these worlds, the first step is to model the atmospheric gas layer. To do this, a research team led by Dr. Yohai Kaspi of the Weizmann Institute´s Environmental Sciences and Energy Research Department, observed variations in the planets´ wind pressure and density, and used this to create a map of the gravitational influence across the atmosphere.

Essentially, Kaspi and his colleagues from the University of Arizona and Tel Aviv University (TAU), were able to find where the sub-atmospheric layers of the planets were contributing “extra” gravitational energy to the atmosphere, in a similar way that a plane approaching a mountain will feel an additional tug from its gravity.

Comparing the observed wind patterns on Uranus and Neptune to simulated “ideal” systems, the team was able to deduce that the weather layer of these planets is no more than 620 miles in depth — a tiny fraction of the overall planets´ size.

To confirm their findings, a probe would need to be sent to the planets to investigate their atmospheric layers. While no such mission is currently planned for Uranus and Neptune, the Jupiter probe Juno will reach the King of the Planets in 2016. The team plan to use the data obtained by Juno, combined with their model to similarly construct a model for Jupiter´s weather layer.

While there is still much work to do, this is an important first step in beginning to finally probe the various layers of our Solar System´s largest worlds.

A paper on the work is published in the journal Nature.


Source: John P. Millis, Ph.D. for redOrbit.com - Your Universe Online



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