Astronomical Society of Coonabarabran

South Pole Sketch-book

by Harry Roberts

The lunar "deep south" is a hard area to study with masses of craters overlapping each other. So I chose to make outline maps of the terrain over two nights in an attempt to sort out the basic features. Since I'd read about crater Newton in Hill's "Portfolio", I hoped to learn something of it too.

By the end of the session I had a rough sketch that showed some of the landforms between Moretus (just south of Clavius) and the southern horizon. "Virtual Moon" showed that libration was not favourable, and that my first sketch at the region did not show the pole itself (Fig 1). On the following night I made a second sketch of the field, hoping to learn more (Fig 2).

The sketches have east to left and south at the top, as if we hovered above the formation (for IAU rotate 180 degrees). This was the way it looked in my C8 with a star diagonal and I find it easier to interpret landforms if they are in terrestrial orientation.

Conspicuous in the centre is crater Moretus, with Short just behind it. During the 50's amateurs spent hours studying a "pit" on the top of Moretus' central peak hoping for volcanic activity.

Below left (east) of Moretus is Curtius, with Gruemberger below right. Far right (half filled with dramatic spires of shadow) is Casatus, with Klaproth below, an amazing sight! And above right of Short was a tangle of overlapping craters: the Newton complex!

Clementine imagery of this area shows Newton is a mix of five or more craters, all of very different ages (Newton is 79 km dia, the others are secondaries A, B, etc). Only under favourable libration can we see much of Newton's crater floor.

Amazingly, four steep, high peaks punctuated the horizon. They looked taller and more isolated than any I'd seen elsewhere on the Moon. All are about 4 - 5km high, and I labelled them "d", "a", "b" and "c". Consult "Modern Moon " page 127 and you will find Whitaker's 1954 hand drawn map. The peaks named M1 and M3 are my "a" and "b" respectively, I think. Wood tells us these peaks are part of the Leibnitz Range, thrown up by the South Pole Aitken impact (ibid, p 126).

Fig 2 shows how libration brings peaks "a", "b" and "c" more in line over 24 hours. Above Casatus a huge isolated massif has appeared, that can also be seen on Clementine imagery. It looks to be 4km or so high and ~90 km long: a vast formation that doesn't seem to be plotted or named in Rukl's "Atlas of the Moon" (Red arrow Fig 2).

Fig 2 also shows a "valley" curving around Newton's west rim, dotted red in the sketch; an interesting unnamed formation.

Enjoy Moon watching.

Figure 1

Figure 2