Plinius region

365 Days of the Moon Weekly Feature Image
February 18, 2018

Click image for full resolution

Image taken through a Sky-Watcher 20-inch StarGate Dobsonian telescope with a Seibert Optics 1.5X Barlow and a Celestron Skyris 236M camera.

Out of the thousands of photos I have taken of the Moon, this one most grabs my heart. There are no spectacular craters or rays or dramatic mountains, but there is a subtle collection of historic and often unnoticed features that make this image special to me.

Do what's the deal? First off, there is that huge lunar spider at lower center. At the core of the sprawling feature is the buried impact basin Lamont, seen as the twin circular ridges at the center of the radial wrinkle ridges. This feature plays hide and seek with the observer. The ridges that form the “spider” are shallow, perhaps no more than several hundred meters high, but often more than five kilometers wide along their considerably longer length. This shallowness makes them disappear when the sun is high and shadows are absent.

To the lower left of Lamont are the side by side shadowed craters Sabine and Ritter. Even into the mid-1960's, these twin craters were considered to be an example of the volcanic origin of lunar craters. Of course, by the 1970's the erroneous 19th century concept of volcanic lunar crater origin was swept aside and the impact origin was universally accepted. But in 1964 the volcanic crater concept was still so entrenched that NASA's Ranger 8 spacecraft was targeted to pass over these twin craters to study their “volcanic” origin. The Ranger results were not conclusive, but did provided more data points contributing to the demise of the idea of volcanic lunar crater origin.

With that bit of history explained, the region below Lamont has an even bigger place in lunar history books... here lies the famed Apollo 11 Tranquility Base where Neil Armstrong planted the first human footprint on the Moon on July 20, 1969. To locate Tranquility Base, notice the three small left to right craters midway between Lamont and the linear gouge of Rima Hypatia at image bottom. These are from the left Aldrin, Collins, and Armstrong, named after the crew of Apollo 11. Tranquility Base lies just south Collins crater.

Back to ----------------- Table of Contents