Posted: June 27, 2006 in Astronomy & Space

Now and then I have episodes of Astronomy, here’s my latest:

Its cold in space, I mean really really cold! Despite the temperature, gravity has a knack of twisting things back and forth causing friction, heat and action.

Enceladus a small shiny icy moon of Saturn, about the size of Arizona or jolly old blighty, has been under the spotlight recently. Professors Nimmo and Pappalardo have this month published a paper in Nature, nailing their theory to the church door.

Why would a 504km in diameter ice ball 1.3 billion Km from Earth (in old money that’s 744 million miles) induce a flurry of thoughts, words, phone calls, emails and calculations in Messer Nimmo and Pappalardo?

Enceladus has a hot spot on its southern polar region. We all know that hot spots are not usually associated with Polar Regions; think Antarctica, think polar ice on Mars.

The professors think Enceladus, which has an errant Hot spot where no hot spot has any business being. There theory is that Enceladus must have changed its rotational axis.

A stable rotational globe has general characteristics such as:



This proposed change in rotational axis was due to a decrease in the density of the equatorial region of Enceladus.

Why would such a change be a reasonable proposition? I hear you cry?

Enceladus orbits Saturn within the ring system and is in a 2:1 orbital resonance with another moon Dione, this constant change in gravitational forces acts to heat the interior of Enceladus up, much like Uri Gellers spoons.

This has caused a diapir (I spelled it right-see here) this is Wikis definition:’ Diapirs commonly intrude vertically upward along fractures or zones of structural weakness through more dense overlying rocks because of density contrast between a less dense, lower rock mass and overlying denser rocks. The density contrast manifests as a force of buoyancy. The process is known as diapirism.’

Here , in this longitudinal section of Enceladus is  what they propose:




The change in axis is in the order of 30 degrees; they propose that this effect of tidal gravitational forces may have effected other moons.The possible subsurface ocean is currently venting water into space making Enceladus the Astrobiologist moon of choice for life Jim but not as we know it.




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