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Monday, 12 September 2011

Ages of Ptolemaeus Alphonsus and Arzachel craters

Photographer: Victor Lupu
Optics: Celestron C8-Newtonian telescope, plossl 20mm, 2x Barlow
Mount: CG5 (EQ5)
Device: Sony CX105 at 8x optical zoom
Total Magnification: 800x
Eyepiece Adapter: 1.25 "
Filter: No
Date: 12/05/2011
Location: Baia Mare, Romania
Processing: video capture, FastStone Image Viewer

          Alpetragius and Arzachel are on the center of the Moon. In captures above, these two craters are the ones that are in the foreground.
The photo below is an image of the area where this craters are located.

          Arzachel is one of the three craters that form a chain of craters: Ptolemaeus, Alphonsus, Arzachel. On Earth, a technique used to realize the age of geological formations is by seeing the effects of erosion of structures.Even if the force of erosion on Earth and the Moon are different, this technique can be used to know the age of geological formations on the Moon too.
One of the best places to see different craters on the Moon to see craters located next to each other, is Ptolemaeus Alphonsus and Arzachel.
         Looking at the photo below, the differences between the three craters are very obvious. Ptolemaeus has a large flat floor with no central peak , and the edge is almost nonexistent in some places. Alphonsus, has also a flat floor, but shows a central peak and crater walls are more robust. Then there is Arzachel , a good example of a complex crater, with terraced walls, and a distinct central peak.

It is evident so far in terms of age of craters, that Ptolemaeus is the oldest, Alphonsus is the middle brother and the youngest is Arzachel.
Why Ptolemaeus do not have a central  peak? After the impact, crater Ptolemaeus formed, magma beneath the crust of the Moon rose through the cracks. Magma, joined and then hardened in the crater forming a flat floor. It was gathered enough lava to completely flood the crater's central peak, but not enough to cover the walls of the crater.

Alphonus crater floor is also flooded with lava, but it was not enough to flood and central peak.
Beautiful terrace walls inside Arzachel crater have remained almost untouched, because of its young age.


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