Messages

1

Moon Zoo Object Collections / Re: Interesting terrain

« on: February 06, 2012, 06:25:30 pm »

Ok science bods, do you know what caused these scrape marks?

http://wms.lroc.asu.edu/lroc/view_lroc/LRO-L-LROC-2-EDR-V1.0/M104725662LE

Sorry, I replied to kodemonkey, but didn't make it to the forums...

I couldn't find this exact spot in the linked NAC strip (this is why an act-react quicklink is often more useful, so that people can zoom out and get a feel for the context). But, from what I do find, I would guess that we are looking at ejecta texture (herringbone pattern) from the large crater in the bottom part of the NAC strip. 

2

Moon Zoo Object Collections / Re: Lunar Features - channels, cooling cracks, pits, domes

« on: January 04, 2012, 05:00:29 pm »

Nice!

3

Moon Zoo Object Collections / Re: Ray Crater exclusion zone

« on: December 27, 2011, 04:22:43 am »

Thanks folks. Best Christmas present EVAAAAAR!!!

And the two-toned ejecta one definitely counts placidstorm.

4

Moon Zoo Object Collections / Re: Dark Halo Craters

« on: December 15, 2011, 03:39:53 pm »

The "black stuff" is a mystery!

I don't think we know what it is. It may turn out to be like the dark-haloed craters; sometimes it's exogenic, other times it's endogenic. I think that is one of the reasons they want you looking for it, so that question can be addressed.

5

Moon Zoo Object Collections / Re: Crater Questions

« on: December 15, 2011, 03:24:00 pm »

This is Rhaeticus A, unlike some of the other craters in the series, such as crater B, there is no ejecta in or around it. Is the crater deeper due to its age, or is it a trick of perspective?

...or, is it because some rilles empty into it?

Rhaeticus A is what we call a partially flooded crater. Both it's inside and outside have been flooded with lava. This covers over the ejecta (which is why you don't see it) and makes the crater shallower than it would be otherwise (because part of the inside is filled with lava). The flooding of the inside may be related to the rille you see coming from the upper right. But, it also may have been flooded from the inside. It's hard to tell at this point.

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Moon Zoo Object Collections / Re: Dark Halo Craters

« on: December 15, 2011, 03:14:55 pm »

Great series of dark-haloed craters, Placidstorm (from post #158 onwards)!

The thing to remember is that there are two types of dark-haloed craters: endogenic and exogenic. Endogenic ones are "from inside"; they are formed by volcanism and the dark halo is thought to be composed of tiny volcanic glass beads. Exogenic ones are "from outside"; they are formed by impact craters and the dark halo is thought to be dark material (probably basalt) that gets excavated from beneath the surface. So, the exogenic craters tend to be nice circles, while the endogenic ones can be any shape. Posts #160 and #162  are endogenic. The rest are exogenic.

Keep it up!

7

Moon Zoo Object Collections / Re: Interesting terrain

« on: December 15, 2011, 03:04:47 pm »

I think we need a new collection of "wedge patterned ejecta." 
I thought we had one.....somewhere.
I'll go look.

I, for one, think it would be a great idea to have such a thread.
By the way, this wedge shape in the ejecta is called an "ejecta exclusion zone".

8

Image of the Week / Re: Monday 5 December 2011 - "Textured" Crater

« on: December 06, 2011, 06:18:19 pm »

Beautiful example of ejecta scouring, where the horizontal momentum of impact ejecta creates this "combed" texture.

9

Projects and Objects Examples / Re: TLP Project - Black Stuff

« on: November 15, 2011, 04:13:39 am »

The only thing I can think of that would be that reflective on the lunar surface is a glass-like material similar perhaps to this Apollo sample below:


http://forum.moonzoo.org/index.php?topic=264.msg6052#msg6052

This could fall in line with my view that there is a brittle surface layer of material around the rim of the crater, now adding the possibility of it being impact melt glass.  So perhaps an impact melt splash can also be partially liquified glass.

Hi Tom128,

This is exactly what scientist think the dark material in and around some craters (like the one I replied to just above) probably is; dark, impact melt splashed on the rim of the crater during formation and in some cases drained back into the crater's interior.

However, such glass will look very dark to the camera, not shiny and reflective.

10

Projects and Objects Examples / Re: TLP Project - Black Stuff

« on: November 15, 2011, 04:04:43 am »

Kodemunkey's black stuff find is quite extraordinary and I have added some additional photographs.  The crater is 5 km in diameter and is located on the lunar farside.   Center  lat 8 N and  long 182.96
http://wms.lroc.asu.edu/lroc_browse/view/M125733619  It really is a beauty!

The black stuff on the rim and interior of this one has actually been documented as being impact melt.  Check out this paper. See figure 3 (you should be able to look at the figures by clicking the figures tab).

11

Moon Zoo Object Collections / Re: Crater chains

« on: October 21, 2011, 06:49:40 pm »

No, that is definitely a secondary crater chain. Basically, a clump of material gets ejected from a crater, the different pieces land along the same trajectory line, but at slightly different times (and therefore distances) creating this string of densely-spaced secondary craters. Many large craters will have several such chains and clumps around them.

12

Cafe Copernicus / Re: CHAT

« on: October 21, 2011, 06:46:02 pm »

LOL! 

13

Image of the Week / Re: And the answer is....

« on: October 21, 2011, 02:33:24 pm »

Well done astrostu - I was VERY impressed you spotted a difference using the first 2 criteria.
You get to keep your degree, your PhD and an Expert Mercury Spotter's badge!

W00t!  I'm actually relieved because (others don't know this) I made my case to you in a LONG-a-$ private message to you and when I got done, I was all, "I really hope I get it right, otherwise I'm going to look like an idiot having gone through all this justification and getting it wrong!"

So I'm both happy and relieved.   Though I maintain, this was NOT an easy comparison.  I still think that even if Jules had posted crescents of Mercury (without Caloris) and the lunar far side, the votes would still be somewhat split.

I'd be curious to hear your reasoning astrostu. As far as I am concerned, none of the criteria are actually useful in distinguishing between the planets in these two images.
 - both images have a lot of plains-like areas
 - there are no undegraded ejecta deposits in the Moon image, so there is nothing to compare to
 - both images display tectonic features about equally
 - and albedo contrast is not demonstrated in any of these images.

As I said originally, this was very hard.

14

Cafe Copernicus / Re: CHAT

« on: October 21, 2011, 02:18:31 pm »

And I thought it was just me....

15

Moon Zoo Object Collections / Re: Interesting terrain

« on: October 21, 2011, 02:03:23 pm »

Boulder tracks, or stress marks in rock?




ID: AMZ1000adx
Latitude: 22.9534°
Longitude: 313.138°
Sun Angle: -83.77°
Scale: 1.42 meters / pixel
Zoom Level: 3

or both? if so where did the boulder come from

http://www.moonzoo.org/examine/AMZ1000adx

These are cooling cracks in impact melt from Aristarchus crater.