Taruntius: [NE/J14] Located on the north shore of Fertility, Taruntius is a wonderful example of a floor-fractured crater (FFC). Take a close look at it. Once you are familiar with the appearance of “normal” craters you will notice right away that Taruntius has an unusually shallow basin. This is because hot magma underneath pushed upward with such force that the entire floor rose a little over a mile to its present level!
Also notice the surrounding material that was ejected from the impact (the secondary craters) and the small crater Cameron that resulted from an object that hit precisely on the northwest rim. (Although Cameron looks small, it is nearly seven times larger than Meteor Crater in Arizona!) Cameron is a simple crater. Can you tell if it is bowl-shaped or does it have a flat floor?1
1Simple 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).
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