Unusual crater - formed by impact into a viscous target?

[Toban]

Hi guys!

Please check this out:
http://www.moonzoo.org/examine/AMZ30000bw
Out of the crater at the bottom... is this "old" lava?! Was the impact so deep, that this has "opened" the ground a long time ago?! I think there is no liquid under the moon surface... so maybe it is very old or it's not lava...

Please take a look! Maybe it is important 

Thanks! 

[jules]

Here's the pic Toban.

Interesting. Could it be another one of these?

[Geoff]

and the coordinates are:

ID: AMZ30000bw
Latitude: 49.2394°
Longitude: 3.63271°

[jules]

Just bumping this up as Toban and I are intrugued by this crater. I wondered if it might be another impact into a viscous target like this from the Crater Questions thread.

The crater at left centre looks interesting - not sure if this is a "bench" crater or something else:


ID: AMZ1002gu5
Latitude: 23.3268°
Longitude: 312.925°

This one makes me think that you had am impact into a not-completely-solidified melt sheet. Here's a link to a paper that shows what happens when you impact a viscous target, as opposed to a solid target (specifically, go to page 1657 and look at Figure 5b). If you look around the rim of the big impact crater in the original LROC strip, you can see some more examples of these kinds of craters.

[jules]

This is the LROC strip Toban's crater is on M104497175LE. Look just top of centre above what I think might be a sinuous rille - it is quite big. It may just be a very large eroded crater.

[Toban]

The "eroded"-idea doesn`t fit, I guess, cause there is a clearly boundary of the "inner ring". The ring fits exact in the crater by keeping a explicit level. Eroded sands, I think, would fill the crater not so balanced and ringlike. Maybe the rills are formed by the cooling-down of a liquid.
Just look at the LROC strip (best to see at the right side of the crater). There are two boundaries: of the former crater ("mound"-like, brightly) and of the ring (more darkly). In the top left, you can see stones lying in crater-boundary and "stopped" by the ring. Rocks are mostly in the crater-boundary and pretty sparse in the ring.
And the craters in the crater are very smooth and softly, so maybe it is another material in the crater. Or it is a sign of erosion   I don`t know...
 

[jules]

I've had another look and I really don't know what is going on here! Unusual and puzzling feature. I think we need a team member to take a peek.

[jules]

Just bumping this up and posting Toban's image again. Curious crater.

ID: AMZ30000bw
Latitude: 49.2394°
Longitude: 3.63271°

[IreneAnt]

Just bumping this up and posting Toban's image again. Curious crater.

ID: AMZ30000bw
Latitude: 49.2394°
Longitude: 3.63271°

Hi All,

This too looks like an impact into viscous material. There is a range of crater morphologies that can result, depending on the viscosity of the target material (plus other things like energy of the impact, crater size, etc.).

Earlier, I gave a link to a paper on the experimental results of impacts into a viscous target. Fig. 5b of that paper shows a crater whose central peak and rim topography are very subdued because of the viscosity of the target.

However, different conditions will produce different morphologies. Another paper (Figure 4b) shows a crater that looks much more like the one above, with no central peak and barely any topography at the rim.

Hope this helps....

[jules]

Thanks Irene! That does help a lot. Well done Toban for spotting it.
There will be lots more out there and now we have place to post them.

[Geoff]

From inside King crater on the farside:


Strip: M115529715LE

This area appears to be a lava flood plain with other viscous impacts nearby and is about a quarter of the way down the strip.

[Toban]

I count more then 3 "viscous"-craters.
I think, that these craters are from impacts in the king crater during the cooling down phase of it.
The whole king crater is full of typical "freezing - strips" (see the LROC strip).
It is obivous to see, that the king crater has a molten past (the crater is big enough to believe easily, that the "king impact" could melt the ground).
The ground of the king crater in this "freezing - time" is viscous and easy to liquefy.
Maybe that is the reason, why "small impacts" could create a crater, which liquefy the ground... they are cheating! 
 

[Toban]

oh, i think, NASA has found "viscous craters" in a "liquid target" too:
http://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lroc-20101102-bowditch.html
[A difference is, that they talk about "bowditch", "bathtube" or "depression" and we used words like "ring" or "crater". And we mainly analyzed the craters in the lava terraces; they look at the terrace itself.]

[IreneAnt]

oh, i think, NASA has found "viscous craters" in a "liquid target" too:
http://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lroc-20101102-bowditch.html
[A difference is, that they talk about "bowditch", "bathtube" or "depression" and we used words like "ring" or "crater". And we mainly analyzed the craters in the lava terraces; they look at the terrace itself.]

Hi Toban,
   I'm not clear as to how this is related to craters in a viscous target? The NASA link talks about a small depression in a highland area. This particular depression is called Bowditch (this is its proper name and not a general name for all such features). At some point, this depression was filled with lava. Then, either because some lava drained out, or because the lava deflated as it cooled, the top of the lava subsided to where it is today. But, the lava left evidence of its former higher level, just like a ring of dirt in a bathtub leaves evidence of the original water level in the tub. So, this feature is nothing like a crater that was formed in a viscous target.  And I don't see any evidence here of subsequent "viscous" craters that may have formed on this lava.
    I hope this clears up any confusion you may have had. If not, please feel free to tell me more about what you are thinking.

[Toban]

you are right. I see I have not the right words to discribe what i mean and so I wrote it to fast and not in detail.
I try it again
For example the good LROC image from Geoff; I think, you can see in the king crater the same hints for a lava-sea as in the NASA image. So I wanted to show, that we talk about the same thing only a little bit different; a cooling lava-sea is a viscous target.
So, there are more hints for lava-seas instead of a bowditch; there a "rings" and unusual "viscous" craters in there: Maybe there are these unusual craters in the old lava-terrace from the NASA-picture too. That would be interesting...