The week of January 4-10 takes us from Lunar Day 21 to 27. This week we will highlight Hadley Rille, viewable at midnight on Monday.
Rima Hadley: [NE/G10] This feature formed as lava from a nearby volcanic vent flowed onto the plains of Palus Putredinus1. The lava cut a deep channel that is wide enough to be seen today in amateur telescopes. It is 75 miles long, one mile wide, and 1,300 feet deep. The sickle-shaped volcanic vent from which the lava spewed can be briefly glimpsed each month. It lies perpendicular to the southwest end of the rille. (Look for it when the terminator is very close, as will be the case Monday evening.)
Astronauts made important discoveries at Hadley Rille. Scientists wanted to get better information on the depth of the Imbrium basin and its age and composition. Hadley Rille afforded the Apollo 15 astronauts an opportunity to examine a deep cross section of the basin. They brought back rock samples that proved that the Apennines were formed as a direct result of the impact that blasted out Mare Imbrium 3.9 billion years ago.
Monday evening should afford a good opportunity to view Hadley Rille. Its width of only one mile would subtend an angle of less than one arc-second, but lines are easier to see than points. You would normally need a 5-inch telescope and good conditions to see this feature. What size instrument can you see it with?
1 Which may be roughly translated as “the Marsh of Great Stinkiness.” (What a vacation spot!)
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 www.skyandtelescope.com 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
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