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Galileo's Moons: 4 at 400, Serious Satellite Video
DrShank
post Oct 20 2009, 12:41 PM
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I have posted 4 new videos on http://stereomoons.blogspot.com
They show each of the 4 Galilean satellites from a topographic perspective.
Each moon is very different in character and this is reflected in the content of the videos.
These are added to the growing collection which started with the Saturnian, Uranian and Neptunian
satellites and add to several already released for Europa. These are also featured in the blog
and the videos themselves are posted on YouTube - http://www.youtube.com/galsat400 -
as part of the ongoing celebration of Galileo's 400 year anniversary. More will be added
over then next few week. I attach some stills from these animations, the details for
which can be found at blogspot!

paul

Tohil Mons Rising over Io
Agenor Linea: Europa's Race Track
Arbela Sulcus: Cutting Ganymede
Callisto's Scars: Asgard Basin
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ngunn
post Oct 30 2009, 02:21 PM
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I've thoroughly enjoyed viewing these images and movies. I'd like to ask a very basic question in the 'probably been answered before but I can't find it' category. How much vertical exaggeration are you using here? Is it a constant factor for all the images? I'm trying to find out what are the actual gradients on Tohil Mons (for example). I've looked in quite a number of places but haven't been able to find a side view or cross section with scales given or an actual slope estimate anywhere. I did find one schematic cross section on p 322(EDIT just looked again and can't find it. Maybe I got the page number wrong. I notice you get a different selection of pages every time you open that link.) here:

http://www.google.com/url?sa=t&source=...agglO4SP0YXAFCg

but I don't know if that's at a one-to-one scale either.

Which is Tohil most like?
This:
http://newsimg.bbc.co.uk/media/images/4502...chan_lg_466.jpg
or this:
http://www.nps.gov/bibe/parkmgmt/images/horses-1945_1.jpg
or this:
http://www.planetski.eu/images/site/k2_5_400.jpg ?
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DrShank
post Nov 2 2009, 02:48 PM
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Greetings,
sorry for the slow response. I was pondering the matter. The exaggeration is different for each and is selected to enhance the topography without letting it look "spiky". The renderer uses jpg files, which convert the real values. To estimate the exaggeration
i would have to translate the jpg values and I havent been able to do that yet. That can be crudely estimated if you know the scales of the images. Tohil Mons for example is about 100 km wide (and 200-250 km long) and 8-to-9 km at its highest. This is not
very steep, which should help answer your second question. It may look alpine close to the summit, but most of it not that steep.
For the icy moons, the maximum relief seen anywhere is only 2 km. To get a view with strong relief, I really have to boost the exaggeration. Eyeballing suggests exag. of 10 to 20.
paul


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ngunn
post Nov 2 2009, 05:11 PM
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Thanks Paul- everything helps when it comes to making that imagined view-out-of-the-window come into clearer focus.

Something was nagging in my memory, and after a bit of searching I relocated this very helpful article:
http://gishbar.blogspot.com/2009/01/boosaule-montes.html

OK, it's a different mountain but it does quote an actual slope value of 40 degrees - the first such I have been able to turn up anywhere - and cites the source of that information:
http://dx.doi.org/10.1029/2000JE001408

It's a small world, eh? smile.gif

Unfortunately I can only access the abstract there.
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ngunn
post Nov 2 2009, 06:59 PM
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And some further digging found this:
http://astrogeology.usgs.gov/Projects/ISPR...isprs_mar03.pdf
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DrShank
post Nov 4 2009, 02:24 PM
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QUOTE (ngunn @ Nov 2 2009, 01:59 PM) *



digging up my old postings, eh? There is a lot of information in the Io topography that has not yet been looked at.
the data is complex, has lots of noise, etc, and Ill be bringing on someone new to help me with that. Slopes can indeed be
locally steep and that is one thing we will be looking at. but they can also be shallow, given that many mountains are
undergoing erosion or slumping. stay tuned for more. . . .


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