image by Jérôme Grenier, Paris, France
The southwest corner of Mare Tranquillitatis is one of the most fascinating areas on the Moon. It is full of diverse landforms, most of which are only elusively visible. The easy parts to see are the craters Arago near upper right), Manners (middle) and Ritter and Sabine (bottom left). Much of the rest of the scene requires low illumination as in Jérôme’s image. Most famous here are two large and rough domes, Arago Alpha (above) and Beta (left) of Arago. Two hills stick out of the top of Alpha - they may be made of more viscous lava than the body of the dome. A second class of difficult to see features here are the rilles that arc around the shore of the mare. Parts of these rilles are broad enough to be seen with a small telescope, but other parts are narrow and poorly known. 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. One of the most fascinating formations is the long mare ridge east of Arago. This wrinkle ridge is associated with Lamont, just off the eastern edge of the image. The top edge of the ridge has a curled look and the broad domed basal part is well seen. At bottom right is another somewhat elusive feature - the crater Aldrin. Finally, notice the lunar Stonehenge within the crater Ritter.
Technical Details:
4 Aug, 2007. Orion Optics (UK) OMC 12″ + barlow 2x + red 23a filter + DMK 31AF03; 500 frames stacked in Registax.
Related Links:
Rükl chart 35
Jérôme’s website
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