Zeeman

The Far Side WtM of the Moon

LO LO

Southeast Far Side: Central Sector

Pre-Nectarian

Minnaert, 125 km

Nectarian

Bose, 91 km Lemaitre, 91 km Numerov, 1 13 km Zeeman, 1 90 km

Early Imbrian

Dawson, 45 km

Late Imbrian

Antoniadi, 143 km Fizeau, 1 1 1 km

This area of the South Pole-Aitken Basin has less fresh mare than the terrain to the west. The transition between the flat floor of the South Pole-Aitken Basin and the rise to the rim occurs at about 70° south latitude, passing through Zeeman. This transition of material may be the cause of the curious pattern of Zeeman's northwest rim.

Antoniadi has impacted on the rims of Minnaert and Numerov. The condition of their walls and ejecta blankets signifies that Numerov is quite a bit older than Antoniadi, and Minnaert much older than Numerov

Southeast Far Side: Central Sector, 55° S to 75° S, 135° W to 180° E/W The South Pole-Aitken Basin ^^ and the South Polar Region

Southeast Far Side: Eastern Sector

Pre-Nectarian

Lippmann, 1 60km

Nectarian

Mendel-Rydberg Basin, 630 km Petzval, 90 km

Early Imbrian

Dawson, 45 km

Late Imbrian

Eratosthenian

Hausen, 167km

The crater Hausen has impacted the eastern rim of the South Pole-Aitken Basin, throwing an unusually deep ejecta blanket onto the floor of the basin. Long before Hausen struck, the Mendel-Rydberg Basin had left its ejecta, now buried by a tongue of Orientale ejecta, which ended on the floor of Petzval.

To review the sequence, first the South Pole-Aitken Basin formed its floor, sloping up to its rim on the right side of the image. Then the impactor of the Mendel-Rydberg

Basin struck, throwing an ejecta blanket about twice the basin's radius. Petzval struck that, but so long ago, there is no sign of its own ejecta blanket. The Orientale Basin threw its tongue of ejecta across Mendel-Rydberg and the rim of the South Pole-Ait-ken basin. Finally, Hausen struck that rim and knocked some of it down the sloping floor of the South Pole-Aitken Basin. The darker area around Fizeau is where the floor levels out. The floor of Fizeau is about 2 km below the rim of Hausen.

Arrhenius

Mendel-Rydberg B

Lippmann

Watson

Hausen awson

Alekhin

Doerfel

Zeeman

Boltzmann

Southeast Far Side: Central Sector, 55° S to 75° S, 90° W to 135° W

Schrodinger B

^xZeeman

Amundsen-

.Ganswindt B

Y "Sverdrup

I GanswifidtM^lde|son

Ash brook jeniunax

Boquslawsk

Near Side

180 E/W

South Polar Cap 70° South to the South Pole

Pre-Nectarian

Amundsen-Ganswindt Basin, 355 km Boguslawsky, 97 km

Nectarian

Amundsen, 101 km Demonax, 128 km Newton, 78 km

Sikorsky-Rittenhause Basin, 310km Zeeman, 190 km

Early Imbrian

Schrodinger Basin, 320km

Late Imbrian

De Forest, 57 km Hale, 83 km Le Gentil, 128 km Schoenberger, 85 km

Eratosthenian

Moretus, 1 1 1 km

This South Polar Cap base image is an orthographic projection from the pole to 70° south latitude. It is derived from Clementine visual data from the NRL. This image, processed by USGS, is from the JPL web page. The far side is in the upper half of this image; the near side is on the lower half. The craters listed by period in the key above are all on the far side. The rim of the South Pole-Aitken Basin extends over the pole to the far side, as shown by the dashed line.

South Polar Cap

The southern rim of the South Pole-Aitken Basin (dashed line) extends beyond the South Pole into the near side of the Moon. The Schrodinger Basin has a nearly complete single inner ring. As is typical of such rings, it has a radius of approximately half the radius of the outer rim. Its smaller companion Zeeman shows no evidence of an inner ring or central peak. Drygalski,even smaller,has a central peak as do Short, Demonax, and others in this size range. It is interesting that, at least in this particular area, there is a transition from central peak to a totally flat floor to a single inner ring as the diameters grow from 149 to 190 to 320 km. The impact of Drygalski on Ashbrook shows the power of the expanding crater. Drygalski has broken through the rim of Ashbrook and the velocity imparted to the material of both rims carries it onto the floor of Ashbrook.

The lighting angle is constant with azimuth around the pole. The depth of craters outside the rim of the South Pole-Aitken Basin is greater than that of those within it, as indicated by the greater degree of shadowing. Craters in ejecta are relatively deeper than those that are formed within basin floors.

Poincare

Schröding Amundse^UJ

- • ■' ^TSr^iHST'' ^Minnaert Flat r . ! JM floor -'Antoniadi

- rJj umerov

SPA Rim \ Pole

90 E

120 E

L04-008M

The Lunar Orbiter 4 spacecraft was nearly over the South Pole when it took this photo, looking to the South Pole-Aitken basin. Note the strong troughs radiating from Schrodinger (the tip of one of these grooves is shown in L04-005H3). Dashed lines show the estimated rims of the South Pole-Aitken Basin and the Near Side Megabasin and the edge of the flat floor of the South Pole-Aitken Basin. In both cases, the rim slopes are so low and the rims are so eroded that they are not apparent in this photo.

Distance: 2753.15 km

Pre-Nectarian

Jeans, 79km Minnaert, 125 km Planck, 314km Poincare, 31 9km

Nectarian

Amundsen, 101 km Numerov, 1 1 3 km Zeeman, 1 90 km

Late Imbrian

Antoniadi, 143 km Hale, 83 km Schoenberger, 85 km

Early Imbrian

Schrödinger Basin, 320km

Eratosthenian

Moretus, 1 1 1 km

_LOS-021H

L05-021M

It helps to stand on your head to understand this photo. The spacecraft was over the southwestern near side; the camera captured Zeeman and Schrodinger by shooting over the South Pole. The South Pole-Aitken Basin extends beyond Zeeman and Schrodinger through Numerov and Antoniadi. A very nice view of Schrodinger and the South Pole is in L05-021H.

Distance: 3917.49 km

Pre-Nectarian

Lippmann, 1 60km

Nectarian

Numerov, 1 13 km Petzval, 90 km Zeeman, 190 km

Early Imbrian

Mendel, 138 km Schrödinger Basin, 320km

Late Imbrian

Antoniadi, 143 km Fizeau, 1 1 1 km

Marconi

Keeler.

ieavisidi

Beijerinck

Aitken

Gagarin levi-Civita,

Paracelsus

Barbier fl

PaviovV^AVe0

MARE (Thomson] INGENIÎ"

MARE (Thomson] INGENIÎ"

L02-075M

The large crater Gagarin has had its floor resurfaced in very ancient times, according to crater counts on its surface. Also the sector of its rim that faces the South Pole-Aitken Basin is lower than the far rim. It is just speculation,but could it have been formed before the South Pole-Aitken Basin and been partly buried by the ejecta blanket of the South Pole-Aitken Basin?

Distance: 1542.58 km

Pre-Nectarian

Cyrano, 80 km Gagarin, 265 km Heaviside, 165 km Ingenii Basin, 560km Jules Verne, 143 km Vertragt, 187 km Zwicki, 150 km

Nectarian

Chaplygin, 1 37km Pavlov, 148 km Stratton, 70 km

Early Imbrian

Keeler, 1 60 km Marconi, 73 km

Late Imbrian

Aitken, 86 km Geiger, 34 km Holetschek, 38 km

Eratosthenian

Plante, 37km

L02-033M

The Keeler-Heaviside Basin is clearly very old. Although the terrain of its floor is a little softened, it is still nearly covered with craters of rather large size (including Heaviside) that are themselves heavily cratered. Keeler is a relatively recent arrival. Icarus is quite near the Korolev Basin (Nectarian, 440 km), on the edge of that basin's ejecta blanket.

Distance: 1454.85 km

Key, features outside of the South Pole-Aitken Basin

Pre-Nectarian

Cyrano, 80 km Heaviside, 1 65 km Keeler-Heaviside Basin, 780 km Racah, 63 km

Nectarian

Coriolis, 78 km Dewar, 50 km Stratton, 70 km Vening Meinesz, 87km

Early Imbrian

Daedalus, 93 km Keeler, 160 km

Late Imbrian

Aitken, 86 km

160lI 180 BW

160lI 180 BW

L05-065M

This photo shows the western South Pole-Aitken Basin. Note the shallowness of the large craters and basins on the floor of the South Pole-Aitken Basin such as Poincare. Van de Graaff is not an elongated crater; it is an overlapping pair of craters. Since neither of its craters appears to have impacted the wall of the other, the two impacts may have been virtually simultaneous, a pair of fellow travelers arriving within at most minutes of one another.

Distance: 1331.39 km

Pre-Nectarian

Abbe, 66 km Boyle, 57 km Hess, 88 km Leibnitz, 245 km Lyman, 84km Oresme, 76 km

Poincare Basin, 340 km Von Karman, 180km

Nectarian

Hopmannn, 88km Leeuwenhoek, 125 km Van De Graaff, 104 km

Early Imbrian

Alder, 77 km

Eratosthenian

Birkeland, 82 km Finsen, 72 km

L05-043M

This photo shows the central portion of the South Pole-Aitken Basin. The terminator is near the 160°West meridian of longitude. The center of the South Pole-Aitken Basin (54.2°South and 168.7°West) is within crater Bose. The Apollo Basin lies just to the northeast of Oppenheimer. Oppenheimer is judged to be Nectarian in age because it retains the terraces on its rim, yet is heavily cratered.

Distance: 1334.59 km

Pre-Nectarian

Abbe, 66 km Cabannnes, 80km Hess, 88 km Leibnitz, 245 km Minnaert, 125 km Nishna, 65 km Von Karman, 180km

Nectarian

Bellingshausen, 63 km Bhabha, 64 km Bose, 91 km Oppenheimer, 208 km

Early Imbrian

Alder, 77 km

Late Imbrian

Maksutov, 83 km

Eratosthenian

Finsen, 72 km

This high-resolution frame shows the floor of the Australe Basin, with its craters partly flooded with mare, thinning toward the main ring of the basin (Amr). Only the central depressions of the craters near the rim are flooded, where the sloping floor of the Australe Basin rises. The tip of Vallis Schrödinger (VS) is resolved here into a chain of secondary craters. Yet note that the far rim of the crater at its tip has also been grooved and debris from that rim has been thrown on the floor of the crater. Although this destruction has been attributed to a horizontal projectile, it may have been caused by secondaries traveling in a higher trajectory, about 45°, and so they would have both vertical and horizontal components of momentum. The horizontal component could produce effects similar to those of a projectile at a low angle. Scale can be determined from the diameter of pre-Nectarian Jeans (J, 79 km).

SPA rim/

SPA rim/

L04-005H2 Sun Elevation: 8.6° Distance: 3512.53 km

Hale (H, 81 km) is young, judging by the degree of detail that is preserved in its terraced wall and the complex structure of its inner ring. Its floor, rim, and ejecta blanket are nearly free of subsequent cratering. However, its rays have completely faded, and so it appears to be Eratosthenian. An arc of the rim of the South Pole-Aitken Basin (2500 km) runs near Hale (see L04-008M). The large-scale ridges and troughs in the lower right come from the Schrodinger Basin. The finer striations at right angles to the pattern from the Schrodinger Basin are probably from the near side crater Demonax (128 km).

The South Pole is at the rim of Shackleton (Sk, 19 km). Even within the terminator, the floors of some of these craters are in shadow. Because the Moon's axis is only 1.5° from a right angle to the Earth's path around the Sun, some of these crater floors are never struck by sunlight and must be extremely cold. Instruments on the Prospector spacecraft have detected hydrogen concentrations here, in a form that must be stable. Is it ice or simply hydrogen? The rim of the Amundsen-Ganswindt Basin (AG, 355 km) is very near the pole, running from the south rim of Amundsen (A, 101 km) beyond Ganswindt (G, 74 km).

Shoemaker (Sm, 50.9 km) is in the shadow that is left of the South Pole. It was named after Gene Shoemaker, pivotal investigator of the geology of impact craters and the founder of the USGS Astrogeology Branch. A portion of Gene's ashes, aboard the Lunar Prospector spacecraft, was sent to impact this crater at the end of its mission.

LO5-021H

Sun Elevation: 3.1°

Distance: 3917.49 km

As shown in LO5-021M, this photo was shot over the South Pole (or under, if you like). Consequently, this oblique view of Schrödinger (S, 312 km), over the pole, has its south rim above its north rim and its east rim left of its west rim. This view is a mosaic of parts of the LO5-021H subframes. This oblique view of Schrödinger clearly shows its internal ring. Note also that its floor, inner ring, and rim are relatively free of subsequent craters, an indication of a young age. Crater counts indicate that it is of the Early Imbrian Period.

Zeeman (Z, 142 km) ) is older than Schrödinger; the ejecta blanket of Schrödinger dominates the ejecta field of Zeeman.

LO2-075H1 Elevation: 19.26° Distance: 1542.58 km

Geiger (G, 34 km) has a fresh, sharp look in comparison Imbrian, these secondaries cannot have come from any with its Nectarian neighbor Aminski (A, 26 km) and an basin. They could have come from Aitken, also Late Imbrian.

ejecta blanket that does not have any sizable craters except The "swoosh" is a development artifact. a few secondaries. Since Geiger has been classified as Late

Cyrano (C, 80 km) is quite deep. The resurfaced floor must its rim and the condition of its impact blanket indicates a have only a thin layer of mare basalt. The heavy cratering of pre-Nectarian impact.

This is our best look at Mare Ingenii (MI), filling the main Although O'Day has been classified as Copernican, its rays ring of the Ingenii Basin (IB, 560 km). The young crater have faded, except on the dark mare, and it may someday be peaked on the rim of the Ingenii Basin is O'Day (OD, 71 km). reclassified as Eratosthenian.

L02-033H1

Elevation: 20.20°

Distance: 1454.84 km

L02-033H1

Elevation: 20.20°

Distance: 1454.84 km c

O IA

Dark mare basalt has seeped into the very old unnamed cra- The mare must be very thin here, just barely resurfacing ter near the top of this image, above Daedelus U (DU, 20 km). parts of the crater floor.

"O

L02-033H2

Elevation: 20.20°

Distance: 1454.84 km

L02-033H2

Elevation: 20.20°

Distance: 1454.84 km

The striations (st) here are coming from Aitken (see the the rims and floor of Aitken Y (AY, 35 km) and Daedalus R next page). These radial patterns of ejecta have marked (DR, 41 km).

L02-033H3

Elevation: 20.20°

Distance: 1454.84 km c

O IA

L02-033H3

Elevation: 20.20°

Distance: 1454.84 km

Aitken (A, 135 km) is very deep, a result of its impactor strik- its wall, ejecta blanket, and far field (previous page). Yet it has ing the fractured, porous ejecta in the rim of the South Pole- received significant cratering on its rim and ejecta blanket. It Aitken Basin. Aitken shows excellent detail in the terraces of is assigned to the Late Imbrian Period.

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