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Home , Antipodes, Birkhoff (crater), Deslandres (crater), Fermi (crater), Lacus Mortis, Lacus Somniorum

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Yu. N. and Zh. F. Rodionova Shternberg State Astronomical Institute, Moscow, U.S.S.R.

Cartographic methods are presently used ern hemisphere are 3891 million km2 or 20.0 to study not only the , but also the Moon percent, and in the 2521 and , and will soon be used for million km2 or 13.3 percent. Over the entire and other planets. These methods will remain surface of the moon, maria-type formations for some time the only possible methods for occupy 6411 million km2 or 16.9 percent of determination of many quantitative charac- the surface area. Figure la presents a dia- teristics of surface formations such as co- gram of the placement of maria-type forma- ordinates of objects in various systems, linear tions within 10-degree bands of by dimenions of formations, areas of flat sur- quadrants. Some 65 percent of all maria for- faces and higher order surfaces, volumes of mations are concentrated within of various objects, and relative indices and char- + 40° to - 10°. acteristics. Thalassoids and large craters over 100 km In the department of physics of the Moon in diameter occupy the same amount of area and planets of the Shternberg State Astro- as all of the maria taken together—16.5 per- nomical Institute (GAISH), cartometric cent. In the , large cra- work was done in order to determine the ters cover an area of 2371 million km2, and areas of the lunar maria and large craters. in the southern hemisphere 3870 million km2. The areas of the maria were determined twice The visible hemisphere contains 1906 million in 1968 using a photomap of the visible hem- km2 of these formations; the hemisphere isphere at a scale of 1:5 million (ref. 1) and contains 4344 million km2. Table 3 presents segments of a lunar globe (ref. 2), and in the distribution of large craters by hemis- 1971 using a full map of the Moon (ref. 3). pheres. Based on measurements of the areas The results of the measurements of areas of of large craters, a histogram has been con- the maria are presented in table 1, together structed of the dependence of the number oi with the data of Westfall (ref. 4) and Shoe- craters on diameter (see fig. 2a). This dis- maker and Hackmann (ref. 5). Table 2 pre- tribution can be approximated by a curve sents the areas of circular maria, measured generated by y = A e-B*. The coefficients from the peaks of the surrounding ridges, and A = +138, B = +0.45 were found by the their mean diameters calculated from the method of least squares. This curve agrees area. well with the empirical distribution of cra- The lunar surface is characterized by ters with diameters of 100 to 300 km accord- asymmetry in the locations of maria. On the ing to the criterion of Kolmogorov. Craters visible hemisphere, flows occupy an area over 300 km in diameter predominate on the of 5937 million km2 or 31.2 percent; on the reverse side, where there are 12 in this range. back side, 474 000 km2 or 2.5 percent. The Figure 2b shows that thalassoids have the northern hemisphere contains 4351 million same dimensions as do the circular maria and km2 or 22.9 percent; the southern hemisphere form a special group of formations, which has 2060 million km2 or 10.8 percent. In the west- already been noted (refs. 6 and 7). The 11

755 756 COSMOCHEMISTRY OF THE MOON AND PLANETS

Table 1.—Areas of Maria Formations Measured by Various Authors (in thousands of km.')

Shoemaker Area Hackmann Rodionova Westfall Rodionova 1961 1968 1970 1971

Visible Side

Oceanus Procellarum 2102 2147 2102 864 830 835 829 439 347 433 436 402 430 408 421 311 311 334 326 318 305 312 303 261 253 240 254 165 180 197 176 107 113 115 113 — 109 77 104 Sinus — 107 291 96 96 99 —101 73 — —65 66 66 —72 64 82 62 — 51 53 55 33 48 49 52 36 — 43 40 — 39 29 40 29 27 99 23 28 22 — 13 19 21 — 14 12 —14 14 16 — Mare Veris — 20 16 12 41 — 14 12 8 10 Mare Struve — — 4 — — — Mare Autumni — 4 3 Mare Aestatis — 4 4 1

Far Side

_ 147 148 151 65 60 54 — — 67 49 50 27 15 — — Mare Pacificus ' 20 — 13 ANTIPODES ON THE MOON 757 Table 2.—Areas of Circular Seas Measured From Surrounding Ridges

Area Area Thousands of km' Diameter, km Note

Mare Imbrium 958 1104 Mare Orientals 725 961 From Cordillera 356 642 From Rook Mountains Mare Nectaris 417 729 From Rupes Altai 134 413 From Pyrenaeus Mare Serenitatis 356 641 Mare Crisium 209 516 Mare Moscoviense 166 460 Mare Humorum 153 442 Mare Smythii 147 433 Mare Ingenii 93 344 Sinus Iridium 52 258 Mare Humboldtianum 51 254 Lacus Mortis 25 180

4.O*./' ^T^ ( ^ 'lO* "N. ^ no* \^ NT . ?0•/ ( to* / \ \m* f ) w o \ i V /ID* Xx ^\ a) A N-. f Xo*

b) /U2%|

Northern Southern Visible Far Hemisphere Hemisphere Hemisphere Hemisphere

Figure 1.—Distribution of maria, areas. 758 COSMOCHEMISTRY OF THE MOON AND PLANETS Table 3.—Distribution of Craters Over 100 km in Diameter by Hemispheres

Number of Craters Diameter, On Visible In Southern Entire km Hemisphere On Far In Northern Hemisphere Surface Hemisphere Hemisphere

100-120 37 46 31 52 83 120-140 26 26 20 32 52 140-160 16 15 12 19 31 160-180 5 11 7 9 16 180-200 5 10 7 8 15

200-220 5 4 4 5 9 220-240 1 4 3 2 5 240-260 2 4 3 3 6 260-280 2 2 2 — — 280-300 2 — — 2 2 300-320 _ _ 320-340 — 4 1 3 4 1 340-360 — 3 2 3 1 1 360-380 — — 1 380-400 1 1 — 1 — 400-420 _ 420^40 — — — — — 440-460 2 1 1 2 460-480 — — — — — — 480-500 — — — — — 500-520 1 ^_ 1 1 520-540 — — 540-560 — — — — — — 560-580 — — 580-600 — —1 1 1 —

formations on the back side over 300 km in diameter correspond to maria formations di- ametrically opposite on the visible side. Fig- ure 3 shows a diagram of the antipodes, listed in table 4. This diagram shows the contours of the maria on the visible side between the ± 60° parallels and their antipodes on the opposite side, arbitrarily shown in the areas diametrically opposite. The roman numerals on the map and in the table represent forma- tions on the visible side; the arabic numerals, the far side. Only Birkhoff crater (342 km diameter) fails to fall within this group. It is on a common diameter with a continental Figure 2.—Histogram of the number of craters, ac- area and the area of highest elevation on the cording to their diameters. visible side. ANTIPODES ON THE MOON 759

-100' -w -to' -«o' -ao o' »»• -40- .»•

4 ITTI5

Figure 3.—Map o/ tfee antipodes on the Moon. Maria features: 1—on the nearside; 2— on the farside; 3,4—thalassoides and craters on the farside (D > 300 km, 200 < D < 300 km, accordingly; 5—on the nearside.

Of the 11 craters 200 to 300 km in diam- 5. Mare Imbrium—1104 km eter on the far side, eight are antipodes of 6. Mare Serenitatis—641 km maria formations on the visible side, and 7. Lacus Somniorum three fall in the same continental areas as 8. Mare Crisium—516 km does Birkhoff. 9. Mare Marginis Yet another pecularity has been noted in 10. Mare Smythii—433 km the distribution of thalassoids and large cra- 11. Pasteur—251 km ters (over 200 km diameter) on the surface 12. —206 km of the Moon: most of them are located within 13. —189 km the limits of 2 mutually perpendicular circles. 14. —269 km The first circle has an inclination to the equa- 15. Mare Ingenii—344 km tor, i = + 37°16' and intersects the 16. —247 km at point n = — 81°45'. It passes through the 17. Karman—198 km following formations (see fig. 4): 18. Poincare—339 km 1. Oppenheimer—207 km diameter The primary mascons are also located along 2. —502 km this circle in Mare Imbrium, Mare Serenita- 3. Mare Orientale—961 km tis, Mare Crisium, and Mare Smythii. 4. The second circle has an inclination i = 760 COSMOCHEMISTRY OF THE MOON AND PLANETS

Table 4.—Table of Antipodes on the Moon

Visible Hemisphere Far Hemisphere

I Oceanus Procellarium 1 Tsiolkovskiy a)—189 km,00 la —250 km, Ib Pasteur—251 km, Ic Gagarin

II Mare Imbrium 2a Mare Ingenii(u—344 km, 2b Leibnitz a)—247 km 2c Karman a)—198 km III Mare Serenitatis 3 Apollo a>—502 km Ilia Lacus Somniorum IV Mare Frigoris 4 Planck—332 km, Poincare "'—339 km V Mare Tranquillitatis 5 —450 km VI Mare Fecunditatis 6 Hertzspring C1>—586 km VII Mare Nectaris 7 Mach—196 km VIII Mare Crisium X Mare Marginis 10 Mare Orientale <0 XI Mare Smythii XII Mare Australe 12 Lorentz—340 km XIV Mare Humorum 14 Mare Moscoviense

NOTES: (1) Basins with bottom partially covered by lava. (2) Diameter of basins in kilometers based on outer edge.

- 52°44' and a = 124°50/ and passes ard—206 km, Swartzchild—214 km, located through: on the third circle, passing along meridians -46°, 134° and perpendicular to the contem- 1. Birkhoff—342 km porary equator, on which are located such 2. Landau—226 km large formations as: Korolev—450 km, 3. Lorentz—340 km —586 km, Oceanus Procellarum, 4. Gerard Q—217 km Sinus Medii, Mare Tranquillitatis, Mare Fe- 5. Oceanus Procellarum cunditatis, and Al-Khwarizmi discovered by 6. Mare Humorum—442 km Farouk El-Baz (ref. 8). We should also note 7. Palus Epidemiarum the meridional placement (along ± 90°) of 8. Mare Nubium such formations as: the Mare Humboldtia- 9. —218 km num, Mare Marginis, Mare Smythii, Mare 10. Mare Australe Australe, Mare Orientale, and Lorentz. 11. —205 km This distribution of large formations indi- 12. Mare Moscoviense—460 km cates the great importance of continued study 13. —228 km of various characteristics along these belts 14. D'Alembert—227 km. (determination of crustal thickness, tectonic, This circle passes through the mascon in age, and other peculiarities). Mare Humorum. Large formations not included in the two main circles include: Planck—332 km, Schro- References dinger—342 km. —295 km, the thalas- soid near Schiller on the visible side (coordi- 1. Photographic Map of the Visible Hemisphere of nates at center 56°S, 46°W)—367 km, Schick- the Moon; 1:5 Million Scale, Nauka Press, 1967. ANTIPODES ON THE MOON 761

J Mare Oriental •:; I

•v.v mascons (mass 20-10 lunar mass) ;.;.;.; mascons (mass 10-10 lunar mass) :::: mascons (mass 5-10" lunar mass) AAAi thalassoids Urge craters D > 300 km O craters 200 < D < 300 km

Figure 4.—Diagram of maria, thalassoides, and craters (D > 200 km).

2. RODIONOVA, ZH. F., Measurement of the Areas of 1961, p. 72. the Lunar Maria and Thalassoids. Astron. 6. PSKOVSKIY, Yu. P., Global Study of the Moon. Tsirk., No. 538, 1969. Priroda, No. 4, 1968. 3. Full Map of the Moon; 1:5 Million Scale, Nauka 7. of the Reverse Side of the Moon, Part II, Press, 1969. Vol. 215, 1967. 4. WESTFALL, J. F., The Areas of the Lunar Low- 8. EL-BAZ, FAROUK, AL-KHWARIZMI : A New-Found lands. Strolling Astronomer, Nos. 7 and 8, 1970. Basin on the Lunar Far Side. Science, Vol. 180, 5. SHOEMAKER, E. M., AND R. J. HACKMANN, Ad- June 1973, p. 1173. vances in the Astronomical Sciences, Vol. 8,