Friday, January 26, 2007

Saturn Mystery


This week's issue of NATURE reports that old theories of Saturn's heat are seriously lacking. It has long been known that Saturn radiates 2.8 times as much heat as it receives from the Sun. This was supposed to be caused by the auroras observed at Saturn's poles. Some completely unknown process would then tranfer this heat to the equator. New calculations reveal that this process would in fact make the equator cooler!

"This unexplained energy crisis represents a major gap in our understanding of these planets' atmospheres," the authors wrote, "we need to re-examine our basic assumptions about planetary atmospheres and what causes the observed heating."

As first reported here last Summer, our Subaru telescope atop Mauna Kea has located a hot spot centred within 2-3 degrees of the South Pole, most visible at 17.65 microns. The hot spot, with the hottest temperatures of the surface, is well within the auroral ring. The aurora DOES NOT cause the hot spot. A closer look by the Cassini spacecraft has revealed an immense tornado-like storm at the pole. Tornadoes on Earth result from a warmer layer of atmosphere beneath a cooler upper layer. Something within Saturn is heating the lower layers of her South Pole.

Today's Cassini photo was taken by the Visual Intrared Imaging Spectrometer. Saturn's night side glows nearly as bright as day. A singularity at Saturn's centre would explain both internal heat and the planet's magnetic field. Because Saturn’s magnetic poles coincide with her geographic poles, the hot spot of a singularity would be centred at the South Pole exactly as observed.

10 Comments:

Blogger nige said...

"It has long been known that Saturn radiates 2.8 times as much heat as it receives from the Sun. This was supposed to be caused by the auroras observed at Saturn's poles."

I've never studied astronomy, unfortunately (I did one course in cosmology and general relativity).

But I remember reading in some popular book, probably published in the 80s, that there was a theory of a small amount of relatively "cold" fusion in the heavy gaseous planets like Saturn and possibly Jupiter.

You only need a very weak rate of fusion in the compressed core of the planet to release substantial amounts of energy.

For that matter, do we accurately know how much of the earth's core heat comes from latent heat from solidification of rock and how much comes from degraded radioactive decay energy, or tidal stresses induced by the moon's orbit?

12:38 PM  
Blogger nige said...

There are quite a few sources which quite threshold temperatures for fusion of hydrogen into deuterium. Actually these numbers aren't important for Saturn, as they are based on self-sustaining fusion at high power as in a small reactor or a bomb.

Statistically, at even much lower temperatures, a few nuclei will collide at much higher than average speed. That's what will drive a low level of fusion at relatively low temperatures.

The Maxwell-Boltzmann distribution shows that you get a wide range of speeds in a gas at pressure: http://en.wikipedia.org/wiki/Maxwell-Boltzmann_distribution

Even if the chance of fusion per nucleus is extremely low, Saturn is massive so there are so many atoms there could be a significant amount of fusion. To release from fusion just a couple of times the heat it receives from the sun is probably easy, because Saturn is far from the sun and doesn't receive that much energy. It needs a negligible fusion rate compared to a star.

12:53 PM  
Blogger nige said...

Can't find anything for Saturn, but see this reference:

http://adsabs.harvard.edu/abs/2000IAUS..202E..75O

Smithsonian/NASA ADS Astronomy Abstract Service

Title:
Can D-D fusion explain Jupiter's excess heat?
Authors:
Ouyed, Rachid
Affiliation:
AA(Nordita, Copenhagen, Denmark)
Publication:
Planetary Systems in the Universe, International Astronomical Union. Symposium no. 202. Manchester, England, August 2000, meeting abstract.

Abstract

We explore the possibility of Deuterium-Deuterium (D-D) fusion in the interior of Jupiter. Our interest on investigating such an energy source resulted from the recent extrapolations of D-D fusion cross-section to eV temperatures which suggest D-D fusion as a potential energy source inside Jupiter. We speculate that D could have been brought deep inside the planet by planetesimals (during the process of planet formation) and deposited through planetesimal/ices vaporization. We estimate that with a modest degree of interior stratification of D (5%-10% of the total D of the planet or 1.0-3.0× 10-4Moplus), during the early stages of the planet formation, D-D energy generation has the potential of contributing to the planet's excess heat while keeping the planet's interior stable to convection. The amount of D needed in our speculative model implies planetesimal/ices vaporization efficiency of 5-10% during Jupiter formation (core-instability scenario).

12:55 PM  
Blogger serge said...

I'm no expert but it seems to me that a singularity inside Saturn would swallow it up in a very short time period.

7:20 AM  
Blogger L. Riofrio said...

HI nige. Sources of Earth's heat are mostly conjecture. Someone named Herndon has advocated fission taking place in Earth and other planets.

Serge, Saturn's singularity would have a mass about half that of the planet Earth. If you descended to one Earth-radius (6370 km) from Saturn's centre, gravitational pull of the singularity would be half what you feel standing on Earth. Since the pressure inside Saturn is millions of atmospheres, you would have many other things pushing you around. Even at this short distance from the singularity, particles would not soon be swallowed.

5:31 PM  
Blogger Rae Ann said...

We were watching the shows about Hawking on the Science Channel the other night, and my six year old asked, "Do we have black holes in our bodies?" I thought that was kind of cute.

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