Author Topic: Monday 23rd April 2012 - Notched Cavities or INA-like?  (Read 4680 times)

Geoff

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Monday 23rd April 2012 - Notched Cavities or INA-like?
« on: April 23, 2012, 06:39:54 am »
User placidstorm posted some Ina-like formations in the Dark Halo Craters thread in December 2011.

I think these look more like “notched cavities” than INA-like formations - see end of posting for references to these features.
These cavities appear to be associated with lava which covers a lava tube or rille, part of which later collapses leaving depressions. I don’t know if that’s what has happened here but this whole region is full of interesting features.

The LPOD Lunar Photo of the Day for 10 August 2007 mentions this area:
Quote from: lpod
A feature, previously unknown to me, is the degraded linear rille segment that extends westward from between Arago Beta and Manners. A similar short but more subtle rille is nearly perpendicular to the Sosigenes Rilles between Beta and Sosigenes A. These two rilles must relate to structures that are now covered by the Tranquillitatis lavas - perhaps whatever is under Lamont. Linear collapse troughs just north of Sosigenes A is evidence for a buried lava tube, another feature from the past of this mare area.


An overview of the features that placidstorm found. This area is in Mare Tranquillitatis north of Sosigenes A crater at approximate coordinates, latitude = 8.1 longitude = 19.0.
Left image: M177508146LE  Right image: M177508146RE






Closeup of one of the “bays”.

The image below gives some context to this feature - the area inside the orange oval is the approximate site of the images above. It shows that there is a rille running underneath the feature and this could help explain how the “notched cavities” were formed. The “feature” crossing the rille is a secondary crater chain.
The Lunar Networks article referenced below the image is well worth a read but does contain a mistake where it refers to “linear rille system in the northeast Mare Tranquillitatis” it should say “southwest”.


Full two kilometer width segment of LROC NAC frame M146858595LE as shown on Lunar Networks 16 Sep 2011
[NASA/GSFC/Arizona State University]


More information about INA features will be found here: TLP Project - INA-like Features and here: INA Images
“Notched Cavities” are discussed here: TLP Project - Notched Cavities in Lava

kodemunkey

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #1 on: April 23, 2012, 08:57:18 am »
That's an interesting find, i think i'll have to spend a bit of time looking around there.

jules

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #2 on: April 23, 2012, 12:23:28 pm »
Interesting stuff. I can see the resemblance to the Ina formation - there are some similarities in appearance at least.

kodemunkey

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #3 on: April 23, 2012, 12:26:12 pm »
Any ideas as to how deep this feature is, or if Ina is at a smilar depth?

Geoff

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #4 on: April 23, 2012, 12:38:02 pm »
Any ideas as to how deep this feature is, or if Ina is at a smilar depth?

This area is a bit confusing as it lies on top of a rille and is bisected by a secondary impact crater! I need to learn how to use the new ACT-REACT tool and see if it shows it any better.

kodemunkey

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #5 on: April 23, 2012, 12:41:15 pm »
I find act react's image mosaic to be too confusing, so i use the WMS tool. I found this while looking in Sosigenes A, which i think is nearby to the area of interest:



What are they?

http://wms.lroc.asu.edu/lroc/view_lroc/LRO-L-LROC-2-EDR-V1.0/M122088757RE

jules

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #6 on: April 23, 2012, 12:55:51 pm »
The ACT-REACT topology line-tool doesn't seem to work on sub-km features. I did try it out on some of the small cavities but with no success. I've attached a slice through the longest cavity which is around 1.5 km long.

kodemunkey

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #7 on: April 23, 2012, 01:07:27 pm »
Does that match Ina?

Geoff

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #8 on: April 23, 2012, 01:27:28 pm »
Just found an article that is relevant to this discussion -

from the 43rd Lunar and Planetary Science Conference: Lunar Meniscus Hollows

which discusses the formation of Ina-like features.

kodemunkey

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #9 on: April 23, 2012, 01:33:45 pm »
Interesting read.

jules

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #10 on: April 23, 2012, 06:45:40 pm »
...which places these cavities/hollows and Ina in the same category. That makes sense to me. This makes Ina a large (and spectacular) well defined example.

jules

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #11 on: April 23, 2012, 07:03:24 pm »
Here's Ina (attachment): Ina is 3km long and the graph shows the depression very nicely.

kodemunkey

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #12 on: April 23, 2012, 07:55:06 pm »
So is Ina just a layer of the moon's surface which in most other impacts just gets turned into ejecta in most cases?

jules

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Re: Monday 23rd April 2012 - Notched Cavities or INA-like?
« Reply #13 on: April 23, 2012, 08:28:45 pm »
I suppose - in a way - yes but Ina isn't just one "layer" though as it comprises 2 distinct materials. It's also not a crater so wasn't formed by an impact. There are several theories but somehow the rough terrain has been uncovered and is lower than the "bubbles" of lava.