The week of December 5 – 11 takes us from Lunar Day 13 to Day 19. This week we will highlight the moon crater Gutenberg, located in the SE quadrant of the Field Map.

Moon Crater GutenbergGutenberg: [SE/K14; L=41°E] Gutenberg crater is not only of historical importance because of its namesake, it shows an unusual sequence of crater development. Gutenberg is a large crater (45 mi. in diameter) that is intruded upon by a smaller crater (12 mi. in diameter–Gutenberg E) on its eastern wall. So far, so good. But take a close look at the moon crater immediately adjoining it to the south (Gutenberg C). These craters have violated the usually dependable rule that newer craters are smaller than the older craters they have intruded upon. Gutenberg C is the older crater, while the larger Gutenberg is the interloper.

Another item of interest is the simple moon crater on the southwest rim (Gutenberg A). Simple craters start with rounded floors then progress to a flat floor resulting from a cascade of boulders that have rolled down the interior walls and settled at the bottom. Rim shadows on bowl-shaped floors will appear as a smooth arc. If the floor is flat because it has been partially filled in, the shadow will be truncated (i.e., the apex will be squared off).


On Tuesday the Pleiades will be 3° north of the Moon. On Wednesday Mars will be occulted by the Moon.


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
Moon Crater Gutenberg – Unusual Sequence of Moon Crater Development
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