Slashdot Mirror
The Mystery of Saturn's Atmosphere
eldavojohn writes "Scientists are being forced to rethink theories on why Saturn's upper atmospheric temperature is hotter than can be explained by absorbed sunlight. 'This unexplained "energy crisis" represents a major gap in our understanding of these planets' atmospheres,' the scientists write. 'We need to re-examine our basic assumptions about planetary atmospheres and what causes the observed heating.'"
> But, we understand ours .
If you read the article you'll find that "these planets" refers to the gas giants. It's a specific phenomenon with as-yet unknown causes, not a general problem with understanding atmospheres.
Sheesh, evil *and* a jerk. -- Jade
--Wait. Hotter than the surface but not hotter than the core. The corona is one to three million degrees kelvin, the surface is around 5800 degrees, and the core is around 13 million degrees.
FairTax baby!
But the sun (and other stars) have more mass than Jupiter and Saturn - that's why the pressure at the core was great enough to start nuclear fusion and "start" the sun at some point 5 billion years ago. Saturn and Jupiter, while they have hot cores under immense pressure and temperature (along with immense gravity), don't have high enough pressure (not enough mass) to kick the tires and start the fusion. So it may not be the same energy or processes at work, as fusion releases WAY more energy than just pressure and rotation alone. /"My God, it's full of stars" - Obligatory.
Particles in solar corona are accelerated by the magnetic field, and the process is more or less well modeled by now; gas giants do not possess that strong magnetic fields. One should note that it's the particles that originate in the core in fusion reactions and are emitted away; however, there are no fusion reactions in the cores of gas giants AFAIK, so we're talking about quasi stationary processes in the atmosphere. This difference is fundamental, and the analogy seems broken to me.
I'm not exactly sure how things like greenhouse gases filter into this problem. Saturn has a cloudtop temperature of about 90K which means that it isn't going to be emitting much heat by Stefan's law which depends on the fourth power of temperature. But then again, Saturn only receives about 1% of the sunlight intensity that we get so it is not light we are shining a bright flashlight on an icecube--it is more like we are shining an extremely dim flashlight on an icecube which amplifies the importance of changes in things like greenhouse gases and emissivity.
One of the things that we can't ignore is the affect of spontaneous radioactive decay. If Saturn is just a ball of gas then it probably won't have very many heavy elements that can decay over time (heavy supernova remnants with half-lives in the billions of years like uranium). But if Saturn has a large hidden rocky core then it is certainly reasonable for it to have significant heat generation which would be insulated by the gases. Of course this is well known since it is what keeps the Earth warm (with the crust to insulate it from space).
Sorry to be pedantic here, but there is no such thing as 'degree kelvin'. 10 degrees Celsius = 50 degrees Fahrenheit = 283.15 Kelvin. It's minor, but important to know in some circles.
One CS student VS 893 DOS games: Let's play oldies
Its interesting that you bring up newton. A 3 body system is in fact chaotic. We have good tools but the predictive power of obital mechanics falls in the same catagory. Fluid dynamics that governs the oceans (poorly understood and the dominate driver of long term climate) and the atmosphere are derived pulely from netwon laws of motion (ok a little thermodynamics as well).
Really this is a dam hard problem. Some of the claims are just to precise to be creidable. When you read the original source you find that things really arn't as simple or as certine as they "popular" versions claims.
If information wants to be free, why does my internet connection cost so much?
I don't imagine there's some mystery heat engine there... just some extra chemical activity that hasn't been accounted for.
Planetary chemical reactions generally run to completion on relatively short timescales compared to the age of the solar system. For example, if Earth were deprived of life there would be no free oxygen left in its atmosphere after a million years or so due to weathering.
Giant planets are mostly hydrogen and helium, so there isn't a lot to work with chemically. There have been suggestions that ongoing fractionation of gases, with the helium sinking to the bottom and thereby releasing its gravitational potential energy, might be a source of the giant planet's excess heat. But even that explanation is a bit marginal, as the lifetime for such fractionation is comparable to the age of the solar system.
Blasphemy is a human right. Blasphemophobia kills.
Doesn't anyone recall the Kelvin-Helmholtz mechanism? It's like people just suddenly forgot it existed.
h anism
http://en.wikipedia.org/wiki/Kelvin-Helmholtz_mec
You'll also find links to it from the Wikipedia pages on Jupiter and, you guessed it, Saturn.
Sheesh.