Enigma of Uranus solved at last

Yahoo! News ^ | 3/10/04 | AFP - Paris

[NormsRevenge]

PARIS (AFP) -

Uranus has puzzled scientists ever since the probe Voyager 2 did a flyby in 1986 and found that its magnetic field appeared to break the planetary rulebook.

The evidence from Earth, Jupiter and Saturn determined that a planet's magnetic field should be like that of a bar magnet, with a north and south pole that runs roughly along the sphere's rotational axis.

But Uranus -- and Neptune, too, Voyager found -- are radically different.

Their magnetic fields are tipped over (the north-to-south line lies midway to the equator or even closer) and there are two north and two south poles, as if the field were produced by two bar magnets.

The reason for this, according to a new theory published on Thursday in the British journal Nature: The underlying structures of Uranus and Neptune are radically different from what was previously assumed about these cold, distant planets.

Planetary magnetic fields are created like a dynamo: beneath the planet's surface, there is an electrically conductive fluid, which is driven around by an energy source.

In the case of Earth, for instance, the planet's solid inner core is bathed in a molten iron-rich fluid, which is propelled around by the planet's rotation and by convection currents, which transfer heat from the core toward the surface.

And in Jupiter and Saturn, which are "gas giants" rather than rocky planets like Earth, the magnetic field is believed to derive from a thick layer of sub-surface hydrogen, compressed by gigantic pressures into an electric soup of protons and electrons, which revolves around a small solid core.

Where Neptune and Uranus differ, the new study says, is that even though they are gas giants, their interior structure is different from those of Jupiter and Saturn.

It suggests that these two outer planets may have only a thin layer of metallic convecting fluid.

This has a big effect on the magnetic field, limiting it to a thin "shell" just under the gassy hydrogen surface. That phenomenon may also cause the field to be tipped on its side compared to the rotational axis and also inflict the "quadrupole" effect.

The study's co-authors are Jeremy Bloxham and Sabine Stanley of Harvard University, whose computer model of the planets' interior strongly replicates the strange magnetic fields detected by Voyager 2.

Hard evidence to back it will only come from a probe to Uranus or Neptune, they admit.

No such mission is being planned for the moment, but scheduled treks by US and US-European probes to Saturn and Mercury should yield exciting new data to test the theory of how planetary magnetic fields are born, they say.

[PatrickHenry]

I've seen your name high up on a list of volunteers for a manned probe. But so far, Planet Seven is preserving its secrets.

[AndrewC]

The headline intrigues me in light of this from the article --- Hard evidence to back it will only come from a probe to Uranus or Neptune, they admit.

[RightWhale]

Seems there was a momentum transfer early in the formation of the solar system from an outside object that is long gone. The explanation of how planetary mag fields are created, and even the sun's mag field, has not been satisfactory. An iron core could generate a mag field, but an atmosphere could also. The fact that earth's planetary mag field can reverse and change strength might indicate a less stable source than the massive iron core.

[Alamo-Girl]

Thanks for the ping!

[Godzilla]

BTW, I didn't know there were rings around Uranus.

Only when you sit on the toilet too long.

[Vermont Lt]

You might want to put some prep H on those rings my friend.

[kevao]

Enigma Enema of Uranus solved at last

[SunkenCiv]

Ping!

[Swordmaker]

Unless it was hit by something REALLY BIG at one time...

It's a gas giant... hitting with something "really big" won't do much to the inherrent spin...

[Swordmaker]

Re: the headline... Headline writers are Idiots...NOTHING is solved by the "Theory" ... it just a hypothesis that needs to be tested.

[Junior]

Sure it will. A lot of that gas is denser than water because of the massive pressures involved, and there is probably a rocky-metallic core in the center. The energy of a massive-enough collision can change even the orientation of all that.

Man, talk about reviving an old thread...

[Swordmaker]

Sure it will. A lot of that gas is denser than water because of the massive pressures involved, and there is probably a rocky-metallic core in the center. The energy of a massive-enough collision can change even the orientation of all that.

I disagree... that fluid/gas would not transfer the physical directionality of the vector of the colliding body... the impact energies would most likely be dispersed in all directions. The force transfers are very inefficient in gas/fluids.

[Junior]

I disagree... that fluid/gas would not transfer the physical directionality of the vector of the colliding body... the impact energies would most likely be dispersed in all directions. The force transfers are very inefficient in gas/fluids.

We may both have been laboring under a false pretense.  It turns out Uranus isn't a gas giant in the same fashion as Jupiter or Saturn.  From Wikipedia:

Uranus is composed primarily of rocks and various ices, with only about 15% hydrogen and a little helium (in contrast to Jupiter and Saturn which are mostly hydrogen). Uranus (like Neptune) is in many ways similar to the cores of Jupiter and Saturn minus the massive liquid metallic hydrogen envelope. It appears that Uranus does not have a rocky core like Jupiter and Saturn but rather that its material is more or less uniformly distributed. Uranus' cyan color is due to the absorption of red light by atmospheric methane.

Also, it appears that scientific speculation is that Uranus' tilt might be the result of an ancient collision:

The reason for Uranus' extreme axial tilt is also not known. It is speculated that perhaps during the formation of the planet it collided with an enormous protoplanet, resulting in the skewed orientation.

Of course, like anything in science this is subject to eventual revision.

[SunkenCiv]

Note: this topic is from March 2004.

Uranus -- and Neptune, too, Voyager found -- are radically different. Their magnetic fields are tipped over (the north-to-south line lies midway to the equator or even closer) and there are two north and two south poles, as if the field were produced by two bar magnets.

Swordmaker has already posted (in 2005). This topic antedates the ping list, so...

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[Monkey Face]

What?

[dforest]

They will deny this under National Healthcare.

[SunkenCiv]

On second.

[Monkey Face]

Who?

[BenLurkin]

Enigma of Uranus solved at last — until the next “scientific” theory comes along.

[djf]

Solved at last? I’d say Uranus remains a far-away mystery and I like it that way.

Lol! That’s what I was thinking.

I’ll worry about mine.
U can worry about urs!