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john_s
post Mar 26 2012, 02:40 PM
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Sorry I missed your talk at LPSC, Phil, but I just checked out your abstract. Nice work! These hollows are fascinating. There seems to be a difference from the Mercury hollows, because those on Mercury are exclusively associated with impact craters, while the Moon ones are often associated with volcanic areas instead. Do you agree? I liked the suggestion at LPSC by Vaughan that the Mercury hollows were due to sublimation of some volatile "scum" that floated to the top of impact melt sheets, but I'm not sure how to apply that idea to lunar volcanic features.

John
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ngunn
post Mar 26 2012, 02:41 PM
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QUOTE (Phil Stooke @ Mar 26 2012, 01:47 PM) *
Rover target anyone?


I wouldn't volunteer to drive it for fear of triggering subsidence and being engulfed. That surface looks poorly supported to say the least.
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Floyd
post Mar 26 2012, 03:59 PM
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QUOTE (James Fincannon @ Mar 26 2012, 10:12 AM) *
They looked like plateaus to me until I looked at another image M142570512. On second thought, I am having trouble visualizing them again. Are these plateaus or indentations?


It's the lighting! We are used to light coming from above in a scene. Print out the picture and flip upside down. --Well worked fine for me for one look, but turned it and now can't get my mid to let go of plateaus regardless of angle--darn visual cortex is not under voluntary control. laugh.gif

[edit] Put the picture on my wall and went for a 20 minute walk. Brain processed image correcty when I returned..


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Phil Stooke
post Mar 26 2012, 07:25 PM
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They are depressions, for sure.

Phil



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stevesliva
post Mar 26 2012, 07:40 PM
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Would be a fun shape-from-shading image. Pretty neat.
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Phil Stooke
post Mar 26 2012, 08:22 PM
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John - I agree about the difference between Mercury and Moon hollows... though some Mercury hollows are up on the central peaks or peak rings of craters and basins, and I'm not sure if that works with the impact melt idea. Hyginus and Sosigines craters contain hollows, but none other that I've found yet.

Phil



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JohnVV
post Mar 26 2012, 08:27 PM
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QUOTE
They looked like plateaus to me

A standard optical illusion

light from the upper left corner or from the lower left
can invert the way the brain "sees" it
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ngunn
post Mar 26 2012, 08:54 PM
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The cure: Arrange for the lighting in your room to be from the same direction as the lighting in the image. Conscious control over the visual cortex is thereby reasserted.

(Sorry - I've posted this before but I couldn't find where.)
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ElkGroveDan
post Mar 27 2012, 12:23 AM
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The voids remind me of what you see when a viscous liquid tries to flow across a rough surface, like paint on concrete or water spilling across hard-packed dirt. I'm not proposing that an analog process is occurring, just pointing out that's what it looks like -- particularly the boundaries inside the hollows the way they sort of curve downward and appear to pull back.


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JohnVV
post Mar 27 2012, 04:05 AM
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The out gassing reminds me of what salt looks like on the concrete after the ice/water has evaporated
I live in the NORTH so ....(N 42.38841 )
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Phil Stooke
post Apr 24 2012, 02:14 PM
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Nice new pic from LRO for the Apollo 16 anniversary. Here's Shadow Rock (Station 13) above left of centre with footprints around it, and LRV tracks at lower right.

Phil

Attached Image


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Phil Stooke
post May 5 2012, 04:21 AM
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I have added the Apollo 16 traverse map (at the LPI website) to the above map to show how accurate it was. The plotted Station 13 was about 50 m off its real location.

Phil

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Eutectic
post May 5 2012, 06:20 PM
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QUOTE (James Fincannon @ Mar 26 2012, 09:12 AM) *
...Are these plateaus or indentations? The craters around them indicate indentations, but then the mind wants them to be plateaus....


They look more like hollows/indentations in the inverted image -- I think the bright regolith-free(?) surfaces in the original image make them look like plateaus. I can almost convince myself of subtle raised aprons around the hollows, as if the regolith were removed upward and outward. Imaging these hollows at different sun angles might be...illuminating.

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James Fincannon
post May 8 2012, 01:50 PM
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Apollo Lunar Surface Journal on Apollo Flags as seen by LRO.

Hope you don't mind tooting my own horn, but I am pleased to be able to post something in the "nasa.gov" domain (it wasn't easy) on something I hope some people find of interest. See following link:
Apollo Lunar Surface Journal Apollo Flags Link
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Phil Stooke
post May 8 2012, 02:03 PM
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Toot away James, this is great.

But I would take issue with you on one point. At Apollo 15 you say there is no clear evidence of a flag shadow, and that is true in the first frames, but not in the last three where a very dark shadow appears and moves as expected. Maybe the orientation of the flag is such that the early frames are casting a very thin shadow (i.e. the sun is in the plane of the flag in the mid-morning).

Phil



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