5-Day Old Moon: Burg, Hercules and Atlas
Ed. Note: Starting this month we have a new series of articles on the Moon and planets by Paul Morow, a relatively new LCAS member who is an avid lunar and planetary observer. You'll find that he has a wealth of experience to share.
The Mare Serenitatis (Sea of Serenity) is located in the Northeast Quadrant of the Moon. This entire area contains a large number of interesting and unique features to explore with a small to medium sized optical instrument. The Mare Serenitatis is an ancient lava flow that was created by an asteroid about 3.8 billion years ago. Today this mare appears smooth and nearly featureless with only a few wrinkles and small craters within its basin. The Mare Serenitatis spills into a smaller lava field Lacus Somniorum, and then further north into the even smaller Lacus Mortis. This is where we find our first crater, Burg, within the small Lacus Mortis lava flow.
Burg is the crater in Lacus Mortis (Lake of Death) that appears as the most prominent feature in this area. Burg's high terraced walls contain deep clefts that demand some attention. Burg's ejecta blanket can be seen thrown out into two main swaths heading north and south from the impact zone. In between these two swaths of material are two well-defined rilles that intersect to form a large T, known as the Rimae Burg. This 100-km rille system west of the crater Burg can show nice detail while using higher magnifications on good nights.
The spectacular pair of craters, Atlas and Hercules, can be found to the east of Burg. Their rims and walls are similar in appearance at low power, but their interiors are very different. The larger of the two is Atlas, and its rim averages about 3 km above the floor. The floor of Atlas appears rough and rille lined. A ring of small mountains can be found at the center of Atlas, instead of a single central peak. Numerous features and small craters can be detected within Atlas while using higher magnifications when the seeing permits.
Hercules appears to be the older of the two craters, due to its walls being more deteriorated than its eastern neighbor Atlas. The terraced walls of Hercules gradually fade into the dark floor. The floor appears composed of darker material and it is more heavily covered with larger craters than Atlas, another indicator of its greater age. The large bowl shaped crater, Hercules G, is the main feature within Hercules that can be easily detected at low powers. The southern walls of Hercules contain a small crater Hercules E. The floor of Hercules contains no sign of a central peak, possibly obliterated by the past crater impacts.
Equipment: 155mm f/9 refractor
Reference: Atlas Of The Moon, By Antonin Rukl (Maps 14 & 15)Published in the April 2003 issue of the NightTimes