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Hesiodus A - The Lord of the Ring


John
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Lovely moon tonight :thumbright:

Hesiodus A is the largest of what are known as Concentric Craters - craters with a raised ring structure within their outer ramparts.

Tonight this little beauty is well illuminated. It's right next door to the much larger Hesiodus, a little to the west of Pitatus on the shoreline of the Mare Nubium.

Even though Hesiodus A is the largest of these concentric craters, it's still quite petite at 14km in diameter. Not always easy to see but tonight the light is right !

I found it nicely displayed with my 120mm refractor at 225x magnification

Many other great features to see as well of course !

Enjoy the views !

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Edited by John
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John,

The David Trang paper concluded that concentric craters were probably formed as a result of igneous intrusions into the crater floors, which is plausible. There is very little evidence however for volcanism associated with any of these craters which you might expect, with the exception of one, Firmicus C, where there is a small deposit of pyroclastic material on the ring, but then again pyroclastic vents are not uncommon over much of the lunar surface. An argument can be made for the less glamorous origin as a simultaneous rim collapse as the crater experienced extensional forces such as during uplift - and Hesiodus A has been distorted by uplift. A collapse origin for the ring explains why these rings are compositionally identical to the crater rims.  Lavoisier and Humboldt have concentric craters very similar to Hesiodus A on their floors, and these are cut by fractures that formed as the floors of the larger craters were uplifted. Younger simple craters very nearby are not cut by these fractures, showing that the concentric craters pre-date the uplift and would have been affected by the deformation, but the younger craters simple craters post-date the uplift so would not have been subject to deformation. The picture of the concentric crater at the start of the Trang article shows how the original ring was deformed by later collapses off the rim which correspond to scars on the crater wall - these 'landslips' and the original ring are indistinguishable as far as spectrum and morphology go, and there is no hint of volcanic products either in or around the crater.

Interesting topic, but I suspect volcanism is not the answer they claim.

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21 minutes ago, Barry Fitz-Gerald said:

John,

The David Trang paper concluded that concentric craters were probably formed as a result of igneous intrusions into the crater floors, which is plausible. There is very little evidence however for volcanism associated with any of these craters which you might expect, with the exception of one, Firmicus C, where there is a small deposit of pyroclastic material on the ring, but then again pyroclastic vents are not uncommon over much of the lunar surface. An argument can be made for the less glamorous origin as a simultaneous rim collapse as the crater experienced extensional forces such as during uplift - and Hesiodus A has been distorted by uplift. A collapse origin for the ring explains why these rings are compositionally identical to the crater rims.  Lavoisier and Humboldt have concentric craters very similar to Hesiodus A on their floors, and these are cut by fractures that formed as the floors of the larger craters were uplifted. Younger simple craters very nearby are not cut by these fractures, showing that the concentric craters pre-date the uplift and would have been affected by the deformation, but the younger craters simple craters post-date the uplift so would not have been subject to deformation. The picture of the concentric crater at the start of the Trang article shows how the original ring was deformed by later collapses off the rim which correspond to scars on the crater wall - these 'landslips' and the original ring are indistinguishable as far as spectrum and morphology go, and there is no hint of volcanic products either in or around the crater.

Interesting topic, but I suspect volcanism is not the answer they claim.

Thanks Barry.

Very interesting :icon_biggrin:

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