[X] My Assistant

[SigurRosFan]

Found at SpaceWeather:

--- Space artist Merry Wooten anticipated the discovery two decades ago:



Wooten had a hunch that Saturn's powerful tides might cause geothermal activity on Enceladus. Her painting of the resulting ice-geysers first appeared in a planetarium show, "When Worlds Erupt," in 1986. ---

I want more. Where are other Enceladus artists?

[Bill Harris]

That escape velocity is still 900 km/h or 560 mph, which is pretty quick. Once we know more about rates and volumes we can make estimates of the pressures involved.

--Bill

[helvick]

That escape velocity is still 900 km/h or 560 mph, which is pretty quick. Once we know more about rates and volumes we can make estimates of the pressures involved.

Which if my calculations are right would be enough to loft some water ~3200m on earth if we had no atmosphere to worry about. Some back of the envelope drag calculations lead me to believe that it would be lower than ~630m once you factor that in, probably a lot less since that's almost supersonic and I can't see a column of water maintaining any sort of integrity under those forces.

In any case these are pretty mean fountains, even if Enceladus is kinda small it takes a lot of oomph to kick something up at 250m/sec.

[Bob Shaw]

Which if my calculations are right would be enough to loft some water ~3200m on earth if we had no atmosphere to worry about. Some back of the envelope drag calculations lead me to believe that it would be lower than ~630m once you factor that in, probably a lot less since that's almost supersonic and I can't see a column of water maintaining any sort of integrity under those forces.

In any case these are pretty mean fountains, even if Enceladus is kinda small it takes a lot of oomph to kick something up at 250m/sec.

If you have a mass of water being ejected upward, is there any chance of a kick being given by the water which follows the initial surge? I'm thinking of a snowball being ejected on top of a boiling fire-hose. Such a combination might cause a proportion of the material to reach escape velocity...

Bob Shaw

[helvick]

If you have a mass of water being ejected upward, is there any chance of a kick being given by the water which follows the initial surge? I'm thinking of a snowball being ejected on top of a boiling fire-hose. Such a combination might cause a proportion of the material to reach escape velocity...

I don't see how unless what is being ejected has a very high percentage of dissolved gases that can subsequently cause a solid block of ice to explode. That would add some "boost" to a percentage of the material. The dynamics of that seem a bit unlikely to me.

I've been trying to think how this would actually work. All I can come up with is that the sources are much more like rift volcanic eruptions than anything we are familiar with involving water\ice. In that case the ejecta would be some mix of mostly ice, some rapidly cooling water and the various dissolved gases.

The fact that what has been detected is seemingly a uniform "cloud" of very small particles would indicate that that is not the case.

[ugordan]

There's also one important factor to consider. Water vapor ejected from the geysers doesn't have to move some 250 m/s to get a chance of escaping. Water molecules at 0 degrees Celsius have a substantial thermal kinetic energy as well and that alone can probably overcome the escape velocity. Some back of the envelope calculations could easily come up with an average speed of a water molecule at a given temperature.

Now, how that translates into macroscopic behavior of larger ice particles I don't know (Brownian motion?). But clearly individual (gas) particles have a very fair chance of escaping into the E ring, regardless of vent exhaust velocities.

The fact the plumes look pretty colimated implies they are kicked up at an appreciable speed. Either that or the water is really pretty cold so the molecules diffuse slowly.