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The Jura and a Missing Rim

May 27, 2004

Image Credit: Giorgio Mengoli

The Jura and a Missing Rim

The Jura Mts are part of the rim of the Sinus Iridum impact crater. There is probably a fault along the Imbrium side of the crater that down-dropped the missing rim, and then later Imbrium lavas covered it. About 50 years ago Harold Urey proposed that Sinus Iridum marked ground zero for the projectile that formed Imbrium - it would have been an oblique impact with the grand explosion occurring near the center of Imbrium. That is wrong - Sinus Iridum was formed after Imbrium. Urey, the chemist, didn't understand geologic superposition - Iridum is formed on top of Imbrium, therefore it had to have formed afterwards. The location of the northern rim of the Imbrium impact basin is controversial because it is so poorly defined. Some people put it under Plato and Sinus Iridum, some place it in Mare Frigoris and others say it is north of there. I prefer the Plato arc because of what I called the tyranny of the circle in The Modern Moon. Basins are closely circular in outline, so if there is little to no evidence for the rim, put it on the circle inferred from the Carpathians and Apennines. And that circle passes under Plato and Sinus Iridum.

Technical Details:
Cassegrain 210mm. and HX516 ccd. Mouseover to see crater names.

Related Links:
Giorgio's Website
An Imbrium-Centered View

Tomorrow's LPOD: Whence the Bessel Ray?


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