Around many large craters, smaller secondary craters can be found caused by falling debris from the main crater forming process. Secondary craters can appear in clumps, sometimes in a herringbone pattern, or more unusually in a line – a crater chain. We haven’t found many crater chains in Moon Zoo. This is probably because they tend to be large features and best spotted using a wide view. Some chains have distinct separate craters while others look indistinct and decidedly fuzzy. Using the ACT-REACT Quick Tool forum regular kodemunkey found a great example of a fuzzy crater chain north of Mare Orientale.
The fuzzy “landslide” effect is due to fragments of debris from the originating impact landing one after the other very close together in a line. The impacts and ejecta have interfered with each other resulting in a string of wispy densely-spaced secondary craters.
A closer look at ACT-REACT shows that the terrain slopes upwards from left to right and that the chain is just over 1km long. The elevation graph shows the expected dips where the debris has impacted.
So where is the parent crater? Secondary craters fall radially to the original impact and up to hundreds of kilometres away. I think the most likely candidate is an unnamed fresh white crater 100 km away.
We have featured crater chains before as Image of the Week. They are fairly illusive but make striking images when you find one. And if you do find one, whether distinct or fuzzy, don’t forget to post it on the forum thread.
Previous Crater Chain Images of the Week:
The ‘Lake of Death’ (Lacus Mortis) lies in the northeastern part of the Moon, north of Mare Serenitatis, and is either an ancient crater or a basin, which has been flooded by lava. It is about 150 km in diameter with the crater Burg, which was formed less than a million years ago, situated approximately in the centre. Lacus Mortis was named by selenographer Giovanni Riccioli in 1651 but he gave no reason for its strange name.
Lacus Mortis also contains one of the few “true” faults found on the Moon and you can see it (marked with an orange arrow) in the image below starting at the southern boundary of Lacus Mortis and going north before finally turning into a rille. (See the first link under Useful Links for more images of the fault).
The western half of Lacus Mortis also contains several rilles, the main one of which is Rimae Burg which is over a 100 km in length and is a graben. Where this rille crosses the boundary between Lacus Mortis and the highlands in the southwest, there are some volcanic cones – see link #4 under Useful Links for more information.
A larger image containing feature names will be found here: LROC Context Image
Burg crater, within Lacus Mortis, is worth exploring as it has many boulder tracks and some nice landslide textures on the western crater wall. See links #2 and #3 under Useful Links for more information.
Boulder tracks within Burg crater
Landslide textures from inner wall of Burg crater, western side.
A true fault in Lacus Mortis: Lacus Mortis Fault
Boulder tracks within Burg crater: A Gathering in Lacus Mortis
Description of Burg crater: Not your average complex crater
Volcanic domes: Volcanoes in the Lake of Death
A mystery! Tidbits of Strangeness
All credit for this entry goes to forum regular kodemunkey who wrote this article:
Hello, and welcome to what will hopefully be the first of many IOTW posts from me.
I was exploring the LRO Data using the WMS Browser and I came across Maginus crater.
(Maginus crater, as seen in the WMS browser, latitude -48.992774 longitude -5.149416)
This is what Wikipedia has to say about the crater:
Maginus is an ancient lunar impact crater located in the southern highlands to the southeast of the prominent crater Tycho. It is a large formation almost three quarters the diameter of Clavius, which lies to the southwest. Just to the north of Maginus is the smaller crater Proctor, and to the southeast is Deluc.
The rim of Maginus is heavily eroded, with impact-formed incisions, and multiple overlapping craters across the eastern side. The wall is broken through in the southeast by Maginus C, a worn crater. Little remains of the original features that formed the rim of Maginus, and it no longer possesses an outer rampart. The floor is relatively flat, with a pair of low central peaks.
The thing about Maginus that interested me at the time was the unnamed crater near Maginus A, as it has a lot of NAC frame coverage. I’m certain that like me you prefer to look at areas with a lot of coverage, if only out of sheer nosiness!
The thing that first caught my eye about the crater was this large, and probably quite deep crack:
The next thing to catch my eye are these huge boulders which are blocking the flow of material down the slope.
These things are quite large, probably at least the size of a house, I wonder where they came from?
Sources and more information:
Your task, should you choose to accept it (even if you don’t ) is to try and figure out how the boulders came to be in their present positions.