Aristillus and Autolycus moon cratersThe week of June 20-26 takes us from Day 21 to Day 27. This week we will highlight the craters Aristillus and Autolycus, located in the N.E. quadrant of the Moon and viewable after midnight on Tuesday, June 21.

Splash rays on the moonAristillus/Autolycus: [NE/F10; L=1°E] Aristillus is a well-defined complex crater, 34 miles in diameter, with a substantial ejecta blanket, terraces, and a central collection of mountain peaks. How many can you count? An examination of the floors of Aristillus and its close neighbor to the south, Autolycus, will indicate that they formed after the lava flows that filled the Imbrium basin. If you are favored by good lighting, immediately to the north of Aristillus you will be able to make out the outlines of an unnamed ghost crater which was almost entirely submerged beneath the lava flows. Notice how ejected material from the Aristillus impact covers the southern portion of this spectral image. Can you make out an unusual dark band that travels up the northeast inner slope and disappears over the rim? When we get closer to full Moon you will notice that Aristillus is at the center of a splash ray system (which means that it is less than a billion years old–a mere youngster in lunar terms!).


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
Aristillus and Autolycus: Well-Defined Complex Moon Craters

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