Geographic Update From Io

We recently learned more about how Earth looks from Space Now, Galileo buzzes a volcano. Gogo Dodo writes: "The Galileo spacecraft will be flying past Jupiter's moon Io (Images here) at an altitude of 124 miles. NASA is hoping that a recently discovered volcanic plume from the volcano Tvashtar will still be there during the flyby as Galileo is set to fly through the top quarter of the volcanic plume. Additional photo of Tvashtar here."

The plume is a incidental

[CheshireCatCO]

This is one of several press-releases I've seen which have come out of NASA about the upcoming pass of Io. I find it interesting that all of them trumpet the plume-pass so highly. Admittedly, it's a "gee-whiz" part of the mission, but there is probably no much science there. As Torrence said in the article, looking at how Tvashtar has changed and making a polar pass to get information of Io's magnetic field are far more interesting scientific goals. Io is the only Galilean moon for which we don't know of the field is intrinsic or induced -- during a polar pass in October of 1999, there was a glitch and the magnetometer was not brought back online in time to do the necessary measurements.

Passing through the plume is important

[Yazeran]

Even though the Gallileo space craft is not designed to directly measure the composition of a gas cloud it passes through, then much can be learned from this pass through the volcanic plume. First of all we will learn the density of the plume (by analysing how much it slows down the space craft).
Secondly, the composition will be more clearly determined by the spectrometers on board, as more 'close up' measurements of the gasses is possible.
These data can then be used to calculate the gas emmision from the volcano, and thus we gain more insight on the volcanic porcesses on IO.

Yours Yazeran

Plan: to go to Mars one day with a hammer.

Re:Passing through the plume is important

[CheshireCatCO]

The plume's density is probably not enough to slow down the spacecraft noticably during its short pass through. Galileo is a large object, and the densities we are talking about here are very low, nanobars of pressure or lower.

I'm having difficulty imagining the spectrometers working better, either. Once a feature is fully resolved, getting closer doesn't make its surface brightness increase, so you don't win there. I'm fairly certain that the plume compositions are pretty well established now (SO2, mostly).

Still, flying through a plume does sound cool, which counts for something.

Re:Passing through the plume is important

[Yazeran]

The plume's density is probably not enough to slow down the spacecraft noticably during its short pass through. Galileo is a large object, and the densities we are talking about here are very low, nanobars of pressure or lower.
Even though, remember that this amall speed-decrease will be integrated over long time (saying that Gallileo will be slightly behind schedule in the future), probably enough so that it would be possible to calculate the density og the cloud.
as to the other, you may be right, as i don't know enough about the spectrometers on board to object.

Yours Yazeran

Plan: to go to Mars one day with a hammer

Re:Passing through the plume is important

[CheshireCatCO]

You're forgetting that Galileo is only going to be around another year or two, which isn't many more orbits. Add to that the fact that there are many small perturbations to it's orbit (leaks in the fuel, small impacts, etc), a small change due to Io's plumes would not appear out of the noise.