The week of October 17-23 takes us from Lunar Day 23 to Day 28. This week we will highlight Reiner Gamma and the Struve/Russel crater, visible through Saturday.

lunar swirl Reiner Gamma on the moonThe week of September 28 – October 4 takes us from Lunar Day 12 to Day 17. This week we will highlight the lunar swirl Reiner Gamma, visible throughout the week starting on Tuesday evening, and the craters Struve/Russel, visible starting Wednesday evening.

Lunar swirls on the moon are absolutely flat features that cast no shadowsReiner Gamma: [NW/J4] Lunar swirls are absolutely flat features that cast no shadows but leave enigmatic whorl-like markings on the lunar surface. No known geological process could have created them, and to heighten the mystery, instruments on Apollo spacecraft measured strong magnetic fields directly over the swirls. For the fanciful, they are eerily reminiscent of crop circles. Of the three swirls on the Moon, two have been found to be antipodal features of major impact zones and mascons. All three of the swirls on the Moon (there are two on the far side) are associated with strong magnetic anomalies.

Struve/Russel: [NW/G2] Close to the west limb you will find an oblong formation that is the result of two overlapping craters which have melted together, Struve and Russel (of Hertzsprung-Russel fame). The fact that there is no hint of a dividing wall is a curiosity. Can you see indications that within the confines of Struve/Russel the lunar surface is curved?


On Friday October 21st, the Orionid meteor shower peaks.


It is highly recommended that you get a copy of Sky and Telescope’s Field Map of the Moon, the very finest Moon map available for use at the telescope. It is available for $10.95 at and on Amazon. All features mentioned in this blog will be keyed to the grid on the Field Map and will look like this: Plato: [NW/D9]

Courtesy of Gray Photography of Corpus Christi, Texas
Lunar photos: NASA / USGS / BMDO / LROC / ASU / DLR / LOLA / Moon Globe. Used by permission

Andrew Planck
Lunar Swirl Reiner Gamma – Flat Features That Cast No Shadows

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