Crater Populations on Lunar Rocks

Home , Chapman (crater)

1973LPSC....4.3255N geometry. Diameter "breccias" Abstract-Approximately niques data 2 made. heavily constant 0.15 loose which 1000 of measurements. (62235, lunar in yield INVESTIGATION small sion, 1972; higher surface, Crater In Four Analytical near *Permanent assuming the © published microns, contrast regolith has Ratios the and on materials scale Lunar Schneider 66075) cratered than independent crater lunar measurements size fifteen been 60016, were flux transport-laterally that of lunar is models satisfied in distributions to and previously. densities address: adapted surfaces. shown applied spall of equilibrium. results space Apollo for 61015, of largest is Planetary Max-Planck-Institut particulate et crystalline surface criteria impact of yield to all NASA FRIEDRICH to al., Crater to of to for interest 17, 66075, 61175, 16 pit of Max-Planck-Institut measured (Neukum four The depend 10,000 The Lunar nine earlier microcratering the obtained rocks: the 1972) different diameters for Proceedings Institute highest criteria Johnson (Supplement craters processes, crater expression non-production rocks, central recognizing Science microcraters on studies, interplanetary for "crystalline" populations and spall-to-pit-diameter H6RZ for the exposure crater and size and GERHARD et which, and a may of JACK Space glass-lined • caused production 4, also fiir average variety al., the Institute, Vol. were Provided a distribution INTRODUCTION Geochimica on for 69935; vertically-of densities wide and range such Fourth equilibrium Kernphysik, in lunar B. 3, filr Center, 1972; contribute the were angles, unambiguously Apollo pp. 3255 turn, rocks HAR.TUNG angle range by NEUKUM* Kernphysik, DONALD and Lunar cumulative of from 3255-3276 as Houston, pits rocks. surfaces et by matter investigated observed on appear primary lunar Morrison Cosmochimica ionization, glass on Houston, 01, 03, 15, 23, 62295, 62235, 61156, 60335, 60315, (3) 16 of of Science the (DP) ratio 3.0 populations, lunar rocks, impact Heidelberg, extent crater lunar A NASA to to surfaces up confirm A. studies. Texas minimum and in of regolith Conference equilibrium for 4.5 shown Heidelberg, an rocks to 4.5. micrometeoroids the but densities Texas of MoRRISON which surrounding Acta) 4 using lunar et for improved Astrophysics rocks 77058 D- times vaporization, only This and 60015, 10- (1) in al., to Germany different 2 value Such 77058 breccias is slope, materials the be binocular absolute extend 5 populations minimum more was crater a 1972; to in Germany. function pit 09, 60135, 60095, for an investigations 10- observed spall and densely diameter understanding rock to equilibrium the are density, Data crater Hartung 15 (4) larger microscope is zones about coefficient, g (Gault of melting, surfaces. from consistent erosional on mass System cratered the densities, on range, crater NE= and and returned a (Ds) two relatively exposure factor state. et et range 68415; 64455. AD;2, rocks may tech- ero- were 10 sizes state A, than with al., al., of (2) of to is 1973LPSC....4.3255N (Shoemaker faces determine the typical face those times ter rocks. ner discuss gated. than sented systematic (Horz (Shoemaker of 3256 interpretation whole 1972). 66075, 64455; objectives effective importantly, division Pertinent metamorphic a cases, zones, Horz Morrison presented central of is magnification given necessary rock Apollo A The Because A Two In densities mass because total variety © the processes et the into "crystalline" 69935. of contrast, are At pit. types rocks et in rocL lunar Lunar Detailed An in may of al. crater the data major measurement et of observational highest low al., outlined spall present distribution The subsequent the 16 (1971), or the in not data al. the of fifteen understanding rocks; be difference and was selected For order on significance diameter 1971) et crystalline et and the rocks. measured impact (1972) spall diameters. absolute diameter, greatly approaching highest of on a known objectives size 40x. these al., al., the this and variety and models above. Planetary "breccias" rocks: Apollo values as distribution mass to physical exposure these zone and were found features convert 1%9; 1970; discussion Under second of over-simplified distribution Morrison rocks is exposure evidence observable the papers that DP, of in of surrounding 60315, Consequently, accurately. The Apollo 16 crater studied processes on rocks observed crater properties that of absolute spall micrometeoroids. rocks the Gault, Gault, of are of Institute of were include the were following of Apollo OBSERVATIONAL objective histories each meteoroid the equilibrium 60335, microscope the et suggestive summarized microcrater "crystalline" measured zone together densities these with density. and were 14 age spall of al. pursued ratio both pit 1970). 1970) a and of the G. governing breccias diameter, (1972). crater 61156, • crater a are on central breccias 12 emphasis investigated, The information. zone rocks observed binocular Provided and crater Ds/ NEUKUM "pitless" highest is polymict as pit as rocks Apollo was of understood a subject and with mass These DP in rather 62235, judged The crater purpose diameters well in densities is their flux were pit density with Table Ds, populations the varies to defined (Morrison these was populations thereby PROCEDURES is was with lowest This microscope implications crater are by elastic et crater was than origin to selected: 62295, of process as characterize distributions was eroded 14 with the investigations placed al. the respect I. revision recorded. significantly approximately erosion meteoritic confined breccias. of high the studies. between selection identified of first to type the on as magnification NASA only by older 68415; and pit, densities improve include of on well this naked glass primary individual (McKay, crater et in objective crater as obtaining a on in a craters, degraded in a al., in as to Astrophysics precise criteria mechanisms "breccias": detailed paper for The by similar this surfaces: eye, Apollo partially Consequently, with crater size truly a the and rather material formation the the 1972). densities micrometeoroids. variety small our were study 1970). first is used without according characterization accurate rock presence being "production" igneous in a fashion fluxes is petrographic rock requires cratering paramount knowledge factor molten more 12 to 01, 09, 60135, 60095, 60015, objective qualitative The was to Hartung 60016, stimulated scale types. Data to very become recognizable basaltic over of surfaces, describe were and distributions Ds/ obtain as 4x, and than to will of highest breccias. 61015, 61175, 61015, of fresh Apollo the described System lunar DP Because a rock a et the geologic high glass-lined rates 80% and, process 3 available. be investi- values The two variety al. a of was to craters. about lower rocks highest variety man- state (1972) Ds/ by grade pre- of sur- sur- cra- and most i.e., main spall This total the on the 16 to by DP on all a 1973LPSC....4.3255N

@ of rocks used in this study. t"" Table I. Summary of PET descriptions = '"I Modec (%) § Rock Massb Sized Surface• Q. Rock Type" (g) Coherence• Opx Opx Plag 01. Glass Aphanitic (mm) History ;-"tl Complex .....ro= 61156 III 58 2 18 - 65 12 - - - 60315 III 788 2 55 20 15 5 - - 0.1 Simplet .... 68415 III 371 2 - 15.2 80 5 - - 0.1 Simplet 5l 318 2 70 25 3 - 0.1 ..... 60335 III - - n.., 62235 III 320 2 45 - 45 - - - 1.0 Simplet .., s ('l) 62295 III 251 2 24 - 57 - - 16 0.4 Simplet -.., 15 xx xx Simplet 'O • 69935 IV 128 2 - - - 0 "tl 2 - 40 55 - - - 0.2 ? 'O 8 61015 IV 1803 C ... 61175 I 543 I - 15 80 - - - - ? .... Q. 66075 I 347 2 - - - - - xx 0.1 Simplet s·::, 8. 1 50 45 - - - 0.5 Complext "' O" 60016 I 4307 - 0 '-< 60095 V 46 2 - - - - 97 - - Complex ::, - Complex i= g 60015 II 5574 2 - - - - 100* - ::, .., z 60135 II 138 2 - - - - 100* - - Simple .., > 57 2 - 100* - - Simplet 0 'JJ 64455 II - - - 0 ::,,;- > 00 > q"' *Large glass coatings. .§ tGood lunar surface documentation. tExcellent lunar surface documentation. "Classification according to LSPET (1972). Type I: Polymict breccia with elastic matrix. Type II: Cataclastic anorthosite. Type III: Igneous "'I")... "' and high grade metamorphic rocks. Type IV: Partially molten breccias. Type V: Genuine glass. t:I bAccording to Lunar Sample Information Catalog, Apollo 16 (1972). (1) Friable. (2) Tough. ! cAccording to LSPET (1972) Thin Section Descriptions. Mode of breccias refers to matrix only. (Opx = orthopyroxene, Cpx = 'JJ '

\.;J N Vt -..I 1973LPSC....4.3255N abundance 60015), 3258 visible. the reductions "halo" structed obtained individual representative "location" similar trated together ponding photography diameter. location tween error area. observers tions. statistical estimate, of areas made pre-existing of diameters reflects tain projectile 10,000 Production The Another pitless significant unobserved The Uncertainties A © standard Additional production bars however, studied, Because indicators zones. of These data in two Lunar via microcraters in detailed the crater surface of with of if of spall Figs. the the however, phenomenon Other the or reduction masses was based a more eventually individuals this these energy of Material populations particular craters Lunar and counting these uncertainties counting measured interest is diameters, the displayed to individual in velocities diameter investigated 1 less than pitless area also pit uncertainties features Planetary through factors, these the surface total on in zones Receiving and was distribution was counts 5% these of by than surface was pit the given. with primarily because up photos. Ds/ uncertainties i.e., surface may identical could of is thereby faces of the craters, spalled subsequent generally diameter to DP square distributions approximately is such 5. illustrated Institute and counted. the the 20%, different data reference 20% is Laboratory obtained refer over-all defined relationship. Both not be The of described effective area observed off are pitless size densities to area as a be arise converted not of into are is root given our to G. resulting of and related some INTERPRETATION actual measurement • related less the distribution by observed Provided a observers. only NEUKUM impacts craters uncertainty including are previous difficult in at from spall to RESULTS mass (LRL) by the field of represents rock, than on a impacting are various Fig. irregular the to a indicated population the pit for lighter zones the crystalline rock of single to for a 5% letters, via during i.e., cumulative distributions shown. 6. diameter et by view variety studies. sum the can these the to observed at of were al. In counts of the microfractured impacts, the face empirical An of magnifications a largest itself, evaluate. all selection T, the was in spallation be similar general, of micrometeoroids. given NASA surface such for measured surfaces B, impact Only example micrometeoroids, the Collectively, of Preliminary of shown excluded. all so N, distributions sizes. each we craters and of sources. size occupied. number a geometry, S, craters data magnification. those Astrophysics visible of excluded crater impact craters. the E, and the A was If to and individual or in micrometeoroids. underlying and distributions such abundances of presented fields conservative the smaller where the Examination a differences original in measurement the are Therefore, W, larger population A of the significant Some were the orthogonal these Ds/ experiments a occurrence of LRL which comparison listed craters and Data total agreement Assuming view destruction DP diameters combined. rock areas few than surf craters. these The correspond the orthogonal determina- is System in which period. rocks are of was between ace in 50%. they per occurred, directly number specific Table or a corres- of the of crater about photos given recon- illus- easily with high Each (e.g., large were was The unit cer- into data The be- the are of to 2 1973LPSC....4.3255N

Table 2. Cumulative frequencies of pit diameters at various magnifications on Apollo 16 rocks (µ, m). @ t""' 4x Magnification = Rock Location Ds/ Dp 500 750 100 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750b (cm2)° "'1= 60016 N 3.4 - 155 80 45 25 13 7 6 5 4 4 3 3 2 39.27 60315 T,d 3.7 46 22 14 8 4 39.27 Q. - = 600315 3.7 46 22 13 8 5 2 2 2 I I 1 19.64 -"ti T/ l'C .....= 5x Magnification "'1 600 800 1000 1200 1400 1600 '-<..... 69935 T 3.3 86 40 16 3 1 1 25.13 ::t."'.....= ..... l'C = 8x Magnification • 250 375 500 625 750 875 IOOO 1125 1250 1375 1500 1625 1750 1875 20{)()b "ti "'1 0 < 60015 N 3.4 75 32 15 5 12.76 .... l.H 60016 N 3.4 211 129 87 50 36 23 17 14.73 Q. N - l'C VI 60315 T2 3.7 56 28 14 5 4 7.85 Q. \CJ C" 61015 T 3.3 - 235 124 66 28 22 IO 14.73 '-<..... 61015 E 3.3 - 294 163 93 58 39 23 19 16 13 12 8 19.63 61175 T 3.0 - 319 196 148 89 59 38 19 18 6 6 2 2 2 2 14.73 l'C =- 62235 B 4.2 - 94 45 24 15 12 9 8 7 2 2 2 2 2 2 15.71 z 62235 w 4.2 114 76 30 13 6 3 1 9.82 rn> 62295 B 4.5 - 73 34 19 9 7 7 4 3 8.34 > 62295 s 4.5 - 20 8 6 3 1 4.91 > 68415 s 3.9 59 29 8 4 4.91 ..... "'"'1 68415 N 3.9 299 162 59 24 11 24.54 0 69935 T 3.3 352 196 85 42 24 14 6 14.73 "C '-<=- "'....t") !Ox Magnification "' 300 600 800 1200 1400 1500 1600b 0 200 400 500 700 900 1000 1100 1360

a 60016 N 3.4 47 44 40 36 17 13 11 9 5 4 3.14 rn '-< 66075 T 3.4 - 293 203 147 95 71 51 33 27 15 11 6 4 4 2 11.94 ..... 66075 N 3.4 - 240 183 135 92 71 53 40 33 21 17 11 7 7 2 11.31 "'l'C 66075 s 3.4 - 159 !08 74 47 37 30 22 16 II IO 8 7 5 2 6.28 s 66075 E 3.4 - 134 93 66 45 34 24 17 12 7 5 4 3 3 3 6.28 68415 s 3.9 65 30 18 IO 4 4.58 1973LPSC....4.3255N

Table 2. (continued) @ J6x Magnification t""' = Rock Location Ds/ Dp 62.5 125 187.5 250 312.5 375 437.5 500b (cm2)° "'1= 61156 E 4.4 69 38 16 7 4 3.18 61156 w 4.4 65 42 18 8 4 0.98 =Q. 61156 T 4.4 96 90 56 32 16 9 1 3.82 -"ti 61156 s 4.4 234 97 42 19 12 6 5 3 5.00 =l'C 20xMagnification 650 700 750 800 850 950 > J()()()b "'1 50 100 150 200 250 300 350 400 450 500 550 600 900 '-<..... 60015 A" 3.4 - 318 176 103 65 36 23 12 10 7 7.62 ::t."'= 60016 N 3.4 -- 114 81 69 43 29 18 1.57 60095 A" 3.4 37 22 14 6 4 0.39 w I.S7 =l'C N 60315 T2 3.7 - 73 47 25 17 8 6 4 4 3 2 2 2 I 60315 T, 3.7 78 71 48 38 26 16 12 9 7 5 2 1 0.78 • 3.14 "ti 61015 T 3.3 -- 282 174 129 82 62 46 "'1 263 174 122 84 65 46 39 3.14 0 61015 E 3.3 -- ....< 61175 T 3.0 --- Ill 85 64 56 46 2.36 Q. 6.36 l'C 62235 B 4.2 - 155 111 78 61 44 37 34 15 Q. 62235 w 4.2 - 138 99 67 47 32 21 IO 8 7 2 2.36 C" 62295 B 4.5 126 78 54 32 23 16 14 14 5 2.36 '-< -- 62295 s 4.5 - 22 14 IO 7 4 4 3 3 I 0.78 =-l'C 64455 B 3.7 173 130 85 57 42 27 20 12 8 4 3 2 1 1 2.83 z 66075 T 3.4 -- 143 104 85 59 42 30 27 23 15 1.57 66075 3.4 --- 86 74 65 52 43 39 32 23 21 16 13 8 rn> w > 68415 s 3.9 - 105 67 35 20 13 1.33 > 68415 N 3.9 246 172 106 77 48 30 3.93 "' 69935 TF 3.3 165 63 35 20 II 8 5 4 3 2 2 I 1.42 "'1 69935 3.3 631 407 257 179 109 83 60 47 4.71 0 T - "C '-<=- 40x Magnification .... 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500 525 500b "'t") "' 0 60015 A• 3.4 - 457 305 210 161 117 85 59 45 33 3.93 a 60095 A" 3.4 53 40 21 14 9 7 4 0.70 rn 60135 A" 3.4 - 351 231 138 92 62 40 23 15 8 4 I I I I 1.37 '-< 60315 T2 3.7 - 70 48 35 31 24 18 16 12 II 0.59 "'l'C 61015 T 3.3 -- 250 180 153 125 104 81 64 58 38 37 31 1.37 s 61015 E 3.3 -- 65 52 42 36 29 0.39 61156 N 4.4 25 21 13 9 6 4 I 2.23 62235 B 4.2 -- 148 110 92 69 51 39 33 33 24 22 16 1.31 t,:')")'lc;: \ll A ") Rl ,;(I 1Q 1, ,,, 1Q ,,, ,,, Q R n ' 1973LPSC....4.3255N

62295 B 4.5 - - 97 57 44 28 20 12 5 5 0.39 66075 T 3.4 -- 123 92 75 59 52 43 37 34 25 23 19 15 14 0.59 @ 66075 s 3.4 -- 144 126 105 94 74 67 59 45 44 36 32 30 20 20 18 1.18 66075 N 3.4 --- 213 205 189 174 152 139 131 99 93 81 73 68 52 51 48 47 45 2.75 t""' 66075 E 3.4 -- 116 103 94 87 78 66 48 44 36 34 32 20 20 19 18 1.18 = 66075 w 3.4 -- 53 50 45 41 38 34 34 30 30 27 25 0.78 "'1= 68415 s 3.9 - 41 31 19 15 9 0.20 68415 N 3.9 - 89 63 37 26 21 12 0.39 =Q. 69935 T 3.3 - 299 194 122 83 64 49 0.79 -"ti 69935 Tp 3.3 127 80 37 24 15 11 6 3 1 0.52 =l'C Counts at various Magnifications "'1 50 100 150 200 300 350 400 450 500 550 600 700 800 900 IOOb '-<..... 60335 T" 3.0 67 64 50 45 29 24 17 15 8 1 1 I 1 1 1 I 3.14 ::t."'= 61175 Td 3.0 - 97 84 70 50 40 34 23 20 17 9 3.14 69935 T" 3.3 852 702 279 98 45 30 18 13 6 2 I 4.89 =l'C • •Average for entire rock ( = A). "ti "'1 bPit diameter (µ m). 0 < CSurface area per magnification and individual rock surface. ....Q. l'C dRepeated counts by different observer (see Fig. 6). Q. C" '-<

l'C \,J =- N z °' rn> - > > "'"'1 0 "C '-<....=- "'t") "' 0 a rn '-< "' sl'C 1973LPSC....4.3255N 3262 illustrated in populations (Fig. additional obtaining observe of that to within distribution distributions Hartung summarizes -1.5 rock - Smooth The © seen 3 glass-surfaces Fig. ters 3) spall open which at Lunar at the 61156 on production a such as 1. a diameters et circles earlier statistically pit counts calculated is breccia large Cumulative size pit curve glass 3 - $ were u and N > in .. e al., obtained a Fig. diameter 1,000 (N, production diameter numerical 100 100 a represent IO 10 Planetary .1~-_,_--~-~ .I I surface, on normalized in 1972; E, also '-----'----'---_., ~-~-~--~ 10 was 1. surfaces is 60135,0 =\) DsfDp on 40 AVERAGE TOTAL 20 TOTAL 69935 the distributions following from i- Because Apollo f--40x-l T, about 3.:=\ ·, FOLD: FOLD: graphically 1. 1--40x-l production significant to found l-20x-l rocks 'l 100 S), COUNTS: = less COUNTS: the Neukum \ measure the of frequency 3.4 Institute date N+S+W was \ T). 37 53 \ conditions. as illustrated size-frequency -2 about measured A= figures are \ A 12 than 1,000 way on 351 60015, of = on investigated \ at .039 and constructed .12 of state. by crystalline its \ lunar on a distributions G. • data are 100 300 et the the 10,000 pit Provided large 14 Ds/ far (:RATER NEUKUM Apollo Dots constructed 09, 60135, 60095, al., absolute µm. statistically µm. diameter for rocks Sp We glass distributions the in values. represent to DIAMETER, size, 1972; pit Fig. complemented The (T obtain rocks, by of 16 et most surfaces. (Bloch number F, diameters crater the specimen in al. samples The 2. of indicating slope fl,ffl Morrison identical the the 10 An NASA of USED: CRATERS 60015,0 Ds,IDp PITlESS INCLUDED 20 TOTAL most suitable DsfDp particularly COUNTS: 644 TOTAL All 100 best populations and "areal actual the FOLD of et additional 55 \ AT flattens The 665 , fit µm 100 COUNTS = 0 al., craters = corresponding Astrophysics show significant fashion. a 3.4\ up • 3.7 173 of 64455. 60015 11 density \ pit \ a slope to our a 1971; et , \ materials to l 1,000 diameters freshly - typical 200 2 per a al., to 625 o on slope o previous was behavior production coefficient" These of Horz values unit µm various 10,000 µm. 1972). production of the Data spall through well fractured measured; area. Apollo and on log-log et Production diame- counts System of suited data similar which al., Figure (A), steepens The surf the surface - 16 1.0 1971; with aces area size size are for to to to 7 1973LPSC....4.3255N some follows micrometeoroid steeper which observational angle, stood slope. where where variable crater and Despite © k faces of Fig. Lunar subtle analytically ... correspond size A ... 0 ,.: z V > "' "' "' ;:: V w :e ::::, ::::, V are N(D) i rock distribution quality (Gault, 2. 1,000 1,000 impact is 100 100 straight-line N, 10 10 Cumulative .I .I distribution. distribution the the 61156,0. 10 and E, differences, is effects, of 'T' f-• 'N' general T, Planetary average the ·-,\\ 1970; angles the 100 complex. and to Note by \oo, cumulative statistical than size various S it A 1,000 considering size Neukum similarity the are = and (Gault, Based may frequency Institute impact .046 does which Crater various typical 10,000 N(D) distribution For data scaling also solid on rock populations number 1973), angle, suffers • and may of distribution example, of 10 areal .... be laboratory = Provided angles a the production CRATER 'E' 'S' 60015. constants; a/3 attributed to a Dietzel, size density \\-- be 100 the from and curves I kaD-a of at DIAMETER, \ significant on of above distribution by of Though craters 1,000 the a sample e coefficients lunar I exposure. microcraters experiments populations the given is shown 1971), small (sin /ffl1 and .10,000 an NASA rocks equation different ir" greater size this empirical 60135 time a for for assuming for 10 Astrophysics is on having of This obtained difference the 'W' different different the may specimen which crystalline than TOTAL t.,\ may shows CRYSTALLINE Ds/Dp average 100 I I effect interpretation 'W': 'N': 61156,0 'T': 'S' 'E' slope constant. \ ~· COUNTS: on be a : : = a diameter 234 25 65 96 69 be 1,000 take surfaces. 4.4 variable various 61156,0. Data I rocks, vertical represented (16x) (16x) (40x) (lb) (16x) a may may rocks. of modified impact into significantly 10,000 the System sides be be A Sur- there The D; account log-log log-log curved impact under- due angles of to a, 3263 the are as to {3, 1973LPSC....4.3255N 3264 and distribution For For For which and a an two from © 69935,0 Fig. Apollo constant Lunar is N impact ,.: :, = ... z "' Ill ... u 0 'E :, ;: "' "' Ill C C > u u .. diameters, 3. true above 1,000 1,000 Cumulative T 16 100 100 may 10 10 and F, .1 .1 l 10 ~--,----,------, breccias. '---~--~-~ ,----,----,------, '------'---~-----' only the TOTAL angle 20 40 shape D 8 40x ... 61015,0E f-40x-l 5 Planetary FOLD: be FOLD: FOLD: /Dp latter density -+--l COUNTS:a ,0 100 -l20xf- when A= t--20x-! = represented ' A D1 i2, 3.3 263 294 of size \ = 65 Note one .052 t-- .27 • we and 1,000 the 8x-l coefficients TOTAL Ill 20 40 Ds/Dp ' Institute being frequency i, 69935,TF the FOLD: FOLD: get N o distribution = 'o.\ COUNTS: D2, 10,000 0 = 2 i2 ( ( difference a r3 I 165 the 127 l1 . ) SID s~n typical or by and G. N1 N1 • - - for BIECCIA 10 distributions analogous li TOTAL ~1)•°' TOTAL a1 40 Provided 20 40 20 - NEUKUM a/3 Ds/Dp allowing 40x a2 Ds/Dp 69935,0 40x--t------l-l8x 8 8 5 CRATER (i2) (i1) surfaces 61015,0 an 20x-+---t FOLD: FOLD: FOLD: FOLD: FOLD: FOLD: FOLD: production = .. ka,D-°'2 COUNTS: ... 1 ." COUNTS:\ in SURFACES 100 -l20xf- a2. the -. = _ = = impact 0 DIAMETER, 631 299 352 T 3.3 T 3.3 areal 282 250 235 86 N2 N2 (s~n 2 SID following by 61015,0 et Ii 1,000 A= ' a (i2) (i1) expressions, of t-- al. the . . . ( density h ~ surface. 5x SID to 1 .24 I'm angle, )•°' microcraters 10,000 NASA be E l1 2 and )•a, a for relationships Also variable, 10 i1, 61015,0 TOTAL Astrophysics TOTAL 20 surfaces 20 Ds/Dp D 8 8 4 61175,0T 5 60016,0N we note /Dp FOLD: FOLD: FOLD: FOLD: FOLD: i1 20x--l obtained COUNTS: COUNTS 100 = = being A= A= T. ... get the 3.0 319 111 3.4 \0 155 211 114 69935,0 namely l-8x-l .27 t-- \ .31 identical \ \ I replaced must Data on various T, System a areal be and = valid. a(D). by i2. 1973LPSC....4.3255N postulated factor from ence angles different tion at rection Equilibrium ships destroyed data distribution the sity, the However, Another After © number is N(D), are faces Fig. Apollo 50 in Lunar are of other in confined 20 TOT 40 40 20 TOTAL which I 8 to D5/Dp sin D5/Dp FOLD, FOLD, AL 4. not a 2 shapes a of not COUNTS, by 500 COUNTS, sufficiently craters different 16 size Cumulative will = = and i1/sin 155 148 94 299 89 246 of somewhat rock 4.2 3.9 populations extreme. of available crystalline subsequent valid the the µm, pits 'i s .. 2 ::, a; 3 ;: u u 6 w Planetary range change craters 68415 to 1,000 1,000 of 100 100 i2 10 10 surf may slope, in ,------,.------,-~ some corresponding of the under average this (N, size where ace L long rocks. 1.4 more at 100 be with observed A= A= observed Institute S) degree frequency a, size present impacts. under Crater expected (e.g., these .16 and .21 exposure 1,000 Note time speculative has the angles range 62235 10,000 populations i1 the • production study to conditions. been as crater = for Provided to will distributions It 10 (B, identical 20 the 10 45°, at shown I 8 may of time, slopes CIYSTAUINE is CRATER andS. the W) one TOTAi. was be shown TOTAL Ds/Dp ecliptic impact, 100 suggested D5/Dp 131 ll4 65 59 A prospect size i2 be as DIAMETER, = COUNTS, rocks on pre-existing = COUNTS, by less extreme areal = sutFAas .21 = qualitatively 20 40 well facing. from 40 1,000 4.2 dependent 3.9 30°) distribution As lunar the distribution. FOLD, FOLD, of I"" not than density as plane, 10,000 105 41 11 microcraters i. NASA investigated. a about over is the rocks Therefore, that consequence, to Unfortunately, of that 10 differences the 62295,0 coefficients be Astrophysics the the then craters the upon -1 lo. if in 100 slope extrapolated B, constant, distribution interplanetary 8 For S range to Fig. cumulative obtained the A 1,000 the -3, = the between on an is .28 8. for shape selenographic 10,000 of changing different a a After Data assumed TOTAL above 20 various 40 TOTAL 20 TOTAL 40 20 however, 20 40 8 surf Ds/Dp difference on 4 I FOLD, and FOLD, pit FOLD,::: FOLD, •T2 • COUNTS, :,1 • s • 62235 COUNTSc COUNTS, various I normalized = System crater of production 126 97 22 20 34 ace 71 4.5 73 70 some diameters we dust sur- relation- the impact B causes will differ- have such den- time size of mo- 3265 di- be a 1973LPSC....4.3255N 3266 © Fig. surfaces different Fig. Lunar ;;- l ! i 0 !! "' i "' 0 ...... :5 ... ;:: ... ::::, ::::, g z > V V v 1.000 6. 5. 1,000 100 1,000 10 100 100 .1 10 Representative 10 10 Cumulative ,------,------,------, '-----'-----'------' .1 .I of 10 observers ,----.-----..---~ ,----.-----..-----, ~--~--~-~ c_ and TOTAL 40 10 breccia __ •OBSERVER 'N' 'S' 20 TOTAL FOLD: FOLD: BRECCIA 8 61175T Planetary COUNTS: FOU):319 FOLD: 100 J.._ r----;-110 COUNTS· 40x 144 1S9 100 __ 111 PIT 66075,0. 1 on size DIAMETER 1,000 1--20x.'"",!_ identical A examples X = frequency Institute _ .36 • ___, Note IVAR. OBSERVER TOTAL [,un] 10,000 0 \000 MAGN) surfaces. COUNTS of for the G. 2 10 • cumulative distributions : the essentially five 97 NEUKUM Provided CRATER 10.000 smallest 100 surfaces. The N 1 DIAMETER, I ! :i 0 "' 0 2: ffi 1,000 agreement 100 10 1,000 et size .1 by identical 10 ,------,------,-----, ~---~----~----~ sizes. of al. the 11m frequency microcraters •OBSERVER 10,000 TOTAL 20 40 8 BRECCIA 5 69935T NASA FOlO:BB FOl0:299 FOl0:831 FOl0:352 .,__ is areal COUNTS: 40_.._ 100 normally -20k PIT I 10 Astrophysics DIAMETER density distributions i--8:r--i -1---1 100 obtained Ds/Dp • BRECCIA 66075,0 TOTAL within (VAR. OBSERVER I ,un] 5x. 1,000 coefficients i-- MAGN.J = 1,000 COUNTS 3.4 2 20%, obtained on Data :852 10,000 various 10.000 except on System all by 1973LPSC....4.3255N the usually passing duction, number. overlap recognizing It overlapping © consistent Fig. representing large production Lunar is be through one transition, The important 7. number recognized Cumulative and equilibrium another. population data slope than Planetary production ranges some of for - and at at craters 2. 12054 frequencies about intermediate this The visually in equilibrium Institute density 0 populations crater and the curves are counted Crater 200 point 60015 figure. µ,m of because gradually populations • populations. to in microcraters 10 pit are PIT Provided normalized for transition 2 are both establish diameter In considered DIAMETER microcraters • • "' " o D V WNAR somewhat practice, one cases. 64455 60095 60015 60135 12054 12017 12073 12054 approaches on by • at • obtained resulting can GLASS the lunar stage. .. • In a to Note criteria pit • NASA be observe NEUKUM t«1RZ however, HARTUNG HO"RZ THIS [wn] with the 10 diameter rocks MATERIALS arbitrary, the the 3 The on in WORK pit most following an a Astrophysics eaie steepening relative a to production et et et variety diameters boundaries upper of al, al, al; the be reliable , a 100 1972 1971 1971 1971 which production used failure of µ, limit, m. because sections glass-surfaces > slope Data 25 is as between of µ, indicated NE(D), a steeper m. System of of craters basis state The the the we after pro- 3267 will can for by to 1973LPSC....4.3255N 3268 Horz tation the ballistic on quantity others. may distribution The microcrater sively fore, diameter> discuss density zel have superposition equilibrium diameter The 1968; Dmin 1. (1971) these loose, quantity above is be © Fig. mechanism finite Neukum the et Absolute can destroyed Lunar the Consequently, is four used sedimentation al. 8. and gives models valid reads lunar concept, be diameter Schematic formula 250 distributions (1971) populations for as 0---~- and 0 u, a: independent z a: ::::, ffi ti: w :E m z neglected, to b as can operating and Dmin an in µ,m. can regolith crater a predict NE(2(a Planetary time by ------TIME------K this constant the equilibrium pointed be Dietzel, direct be as production, = of gives In development PRODUCTION approaches form b cumulative models derived is densities. defined the defined addition, (Marcus, 1113 the though TRANSITION -2))/( surface that on Institute on approaches superposition a x crater out only a hard crater 1971) of general D. lunar transition, > of crater 'TT· by distribution. from that it D above, 2. according for of G. the the lunar An 1%4, formed is are infinity. • b< the represents density The equilibrium rocks, a superposition. Provided NEUKUM 2 the an -a)t microcraters development expression expression analytical crater better the relation and toward rocks infinite 1966, case 13 dominant may of ) by equilibrium general x The i.e., expected to subsequent population et n- EQUILIBRIUM by suited a mmin be over 1970; the Gault al. establishing expression the mmin distribution < 2 the density, Note model has model , derived for applied where 2 diameter able process NASA geologic of on expression to is Walker, largest = populations. (1970), the the for crater where describe not bm hard to gradual impacts. Astrophysics D crater equilibrium for NE(D), only destroy which considered from of can (mmax of been the crater a lunar periods Soderblom populations 1967; the crater particular transition the the for to only be 00 size Neukum equilibrium Ballistic in developed is rocks 100¾ the target CJ 0 0 ii -' IX II.I II.I ::::, 1/1 C (/) IX II.I either craters C 0 I- Chapman has development ro destruction terms obliteration destruction of a Data distribution ). distributions. target here. between well-defined time. Because a (1970), crater are neglecting crater System DP diameter, and sedimen- of with There- crater. exclu- Based which or crater crater et Diet- size and and Ds. al., we pit by on of in 1973LPSC....4.3255N The limited impact Dmax tion tion production we This rock of tion target written, the To set © in of corresponding < opposite means Fig. ufc where surface Lunar crater. establish target the oo, the range events 9. the sense relationships Schematic distribution an and crater we relation Thus, end are impact Planetary the that call 8 II.I 5 Cl > ::, not II.I II.I g u ij 0:: u. !i:i ::, :::E ..I 0:: of to will criteria the of it only the will event large the frequent would a at discussed, destroy minimum lunar Institute "D- Crater be pit equilibrium smaller for craters with 2 rock approximately probably diameters range destruction enough populations the • a crater LOG equilibrium Provided spall diameter sizes. see may b11a= target of SPALL state. require Fig. size equilibrium". distribution to destroy be can DP Ds on DIAMETER frequency crater. by of 9. close correct lunar the be The an a crater larger NASA quantitatively existing the to rocks This end De the distribution reflects the for same For size impact of Astrophysics large is a production the crater an a limited distribution size conservative the idealized craters equilibrium in event as the recorded by flattening size the Data equilibrium a to state in later pit representa- range. destroy for this System diameter distribu- assump- because may impact, a of range. lunar This 3269 the the be 1973LPSC....4.3255N

follows

3270

where sion

increasing

coefficient,

Dsl

to coefficient equilibrium,

limits

ratios

with

specimen through of

slope,

number

cients, values

rocks, slope.

cal density

A few

ity Apollo

1 the tween these, the

cm.

not

measured

applied

The

Such

e:ff

range

model

with

cases,

defined

order

quite

These

the

between

3.5

ective

and

For

ratio

rocks

Lunar

if of

constant

12,

analytically

absolute

coefficient

and

the

the scale

comparison

Thus,

measured

will

observational areal

A(Ameas).

0.7-1

even

degree

perhaps

case the as

varies

gives

especially

14,

the

simplifying

constant

and

to compare

distributions

accuracy on

1.5

and

was

with

larger

destruction

lines

values

not

where

greatest

and

for

equilibrium

terms

density

measure

2.7

one

Planetary

though

slope,

value

reached

not

different

significantly

indicated

and

numerical

given

being

probably

and

other

value

densities

Ds/Dp

derived

rock

This

microfracturing

the

between

for

only

rocks

the

coefficients,

measured

DP/

the

4.5 a

the

data

our

diameter

cases,

Institute

expected

quantity

on line

breccias,

may

ratio

earlier.

range,

Ds/Dpratios

equilibrium.

from

corresponding

production

areal

equilibrium

3. above

crater

values

not

measurements,

equilibrium

the

from Aana1.

calculations

for

intersected

influence

shown

the

furthermore

have

analytically

mind,

occurs.

being

log-log

=2(a-2)

crater

rock

•

value

DP>250

for

densities

relationship:

various

was

NE=ADs

suggest

for

there

Provided

NEUKUM

given

are

0.15.

A(Aana1.)

we a

variation

crater

determined

density

given

distribution

also

Ds/Dp=

the

proximity

surface

Table

plot and

rock

equilibrium

may

state,

transition

This

rock,

the

DP/

equilibrium

some

rocks,

µ,m.

(Dp)°'-

that

must

considerable

must

by et

areal

obtained

vary

derived

shown

cratering

populations

al.

crater-diameter

classify the

based

but

coefficient,

However,

the

can

may

4.5

cases i.e.,

materials.

expect

Agreement

density

reading

NASA

with

the

surfaces

on by

(crystalline

having

treat

dependent

distributions

known.

may on

define

and

two

using

minimum

Ameas.l

Figs.

surfaces

drawing

areal

event

exposure

Astrophysics

different

compared

deviation.

the

extended

coefficient,

::s;

surfaces

Ameas.

glass-lined

also

measured

2 - a

Thus

this

20%.

variation

are

Aana1.

problem

crater

may

is equilibrium

standard

simply

through

reality

vary

coordinate

fair,

3.0

with

rocks)

analytical

slope,

equilibrium

the

which

Thus,

values time

line

exceeds

equilibrium

the

with

the

with

and

Data

density

With

for

however,

less

Ameas.l

areal

pits

densities

areal

from

the

because 2

the

quantity

production

cumulative

-region

within

For

System

have

one

values

measured

Although

-2

than

may also

the shown

slope,

average

expres-

analyti-

density

1.5.

Aana1.

coeffi-

Ds/Dp

given

slope

lunar

qual-

areal

2 - a

deal

The

Ds.

in a

and

For

the

2.7

be- for

in 1973LPSC....4.3255N there the zone which be our decrease densities expected photograph © model, of Lunar appears a rock the in on which and the more different to retains Table to Planetary and "Crystalline" 60315 62235 61156 62235 68415,lS 12006 68415,lN 62295 12038 12051 12021 12017 "Breccia" 12063,106 12047 12053,37 61175T 61015 61015 60016 66075 66075 66075 66075 14053 69935 66075 14318 14306 14321 14303,13 12073 14305, effective explain *Average tNot be assumes areal recent Rock the 3. (III) (I) (II) (II) (I) (I) T W W central B another (I) (B,) (I) T B T T E N N E W S (D,) determined; Comparison density types idealized Institute all for event destruction Crater the effects coefficients of glass all unknown measured Ds/Dp Apollo rocks. 4.5* 4.5* 4.5* 4.5* 4.5* 4.5* 4.5* 4.2 4.4 4.5* 3.6 3.7 4.5 4.2 3.9 4.5 3.9 3.4t 4.5 3.0 3.3 3.5 3.4 3.5 3.4 3.3 3.4 3.4 3.4 3.3 3.4 3.4 would • populations typical sketch of Provided pits. and measured 12 radius on value have The in give crystalline parameter Apollo Ameas. Ds 0.12 0.19 0.13 0.11 0.12 0.12 0.13 0.18 0.24 0.17 0.14 .6 0.17 0.16 0.28 0.21 0.21 0.16 0.39 0.64 0.44 0.21 0.40 0.15 0.18 0.31 0.27 .7 0.20 0.27 0.27 0.36 0.24 0.35 0.33 .6 0.20 0.36 0.38 by on Fig. for parameters is and destroyed are the lunar exact the 2 14, 12, breccias. 10. NASA calculated unknown rocks. Aanal. 0.15 0.15 0.15 0.15 0.15 0.15 0.18 0.15 0.18 0.15 0.15 0.16 0.15 0.16 0.17 0.19 0.19 0.20 0.20 0.20 0.22 0.20 0.15 0.20 0.20 0.20 0.20 0.20 diameter rocks One which values and Astrophysics might 16 a causing rocks. nearby maximum governs Ameas. Auna!. for at of 0.7 0.8 0.8 0.7 0.9 0.9 0.8 0.9 0.9 1.3 3.2 2.3 2.7 2.1 1.2 1.1 1.3 1.3 1.3 1.9 1.1 1.2 1.4 1.8 1.8 1.4 1.4 1.4 1.9 1.2 1.7 1.8 expect present. destruction, equilibrium such older Data the that an System Therefore, ease pit. apparent the cannot crater Thus, spall with 3271 1973LPSC....4.3255N 3272 population equilibrium. one densities tions faces long not period, better surfaces surfaces densities cratered craters deviates These Examples ways "equilibrium" ous may nificantly may 2. If, 3. tumble must © interpretations. to be tual population. spall ing Fig. proximity be with N,E,T,S,W), Lunar Constant Extent display criteria than however, this until surfaces considered in drawn: central from have 10. at of zones may postulate-based on greater the of this 20%. category: with repeatedly, all. and drastically Close-up It different they of of varying be are, (dashed lower the production (Width will pit surface more may, many Planetary crater As n- (somewhat the of a as locations Nevertheless, the also than same of the 2 well less to 62295 high indicated photograph surface densities of of slope. events circles) craters course, is 62235 establish highest surfaces crater density frame finally number course, different Ds. 1000 favorable i.e., crater documented Institute as and size younger) (surfaces distributions, demonstrating on are Note 50%, As approximately (surfaces that µ,m, with densities valid than earlier, reach of must indicated exposure for density an densities. of of still "equilibrium" the (black also rock though exposure G. • spall they different the additional exposure the the only craters Provided all lack either be NEUKUM B,S) the equilibrium. 66075,0 zone dots) rock T using the more optimum same the that for possess in observed if relative geometry and 1 by as of We suggest We of cm.) and one the is be remain uncertainty the the individual other exposure geometries, by a better displays the extending considered et added geometries likely W), rock criterion, general in effective For transition the measured can 60315 al. conditions. big paucity at the solid and comparison NASA and crater This surfaces; are demonstrate accuracy arguments-that can constant. least it production angles. identical (surfaces the rule 66075 destruction is to that faces of different Ds/Dp angle to in the stage associated Astrophysics potentially the will represent actual, that state one small the spall they The the extent a value. (surfaces center. following may only are However, sketch still of If surface is such while events as following zone crater can diameter more T1 the that from indicated or exposure well rocks an accumulate Note result of after depicting and transition with be surfaces Data absolute equilibrium correspond only such crater within diameters as the the one which the T,S,N,E,W). densities judged conclusions eroded, operat- T2). 61156 during System in it the close the n- n- rocks rocks when another, the must ac- ambigu- reaches popula- 2 2 crater crater crater are is state. slope slope more to (sur- this sig- not did be- on al- be all to in 1973LPSC....4.3255N

tion 62235 66075 equilibrium.

limited 66075

events of

66075 sess equilibrium. original

frequency

cially with

Table are ues

surfaces,

60315

61015 61175 62235

60016

62295

66075 68415

69935

Rock

Maximum

Criterion

given

for

given

indicates

"equilibrium"

different

for

Lunar

Erosional

Table

Evaluation

"glass"

T,N,E,S,W

rock-surface

Locations

and N, E,

given

the

for

T1,

the

T,E

rock N,

B,S

value

and

may

Surfaces

criterion

The

Apollo presence

comparison

quality

measured

physical

the

rock

surfaces

Planetary

differ

state

62295

only

Ameas.

Aanal.

(>1)

various

observational

Morrison

crater

X X X X X

X X X

X X

for

All

surface

concluded

has

drastically

surfaces

rocks,

properties

equilibrium

other

statistical

COMPARISON

Here

Institute occur

areal

surface.

this

original

criteria

been

with

Crater

tumbling)

60016

populations.

History

Simple

for

(no

category

these

values.

their

the

are

overlap

68415

with

larger

61015

Low

interpretations

Rounded

densely

Surface

surfaces

the

populations

cratered

interpretation.

62235

with

four

Data

different

the

optical

percent

We are:

maximum

crater

cratered

the far

criteria

and

System

and

uncratered

T T2:

likely

likely likely

yes

doubtful doubtful

find,

Equilibrium

60315

may

cratering

surfaces

doubtful

doubtful,

limiting

that

inspec-

sizes.

Wand

values

rocks

Apollo

espe-

pos-

and and

val-

3273

are

for

the

T1,

no 1973LPSC....4.3255N 3274 production production 60016 granular intergranular we close herency Similarly state. 62295. (Shoemaker cratering sities et OBSERVED LITH REGO- al. None have © ence attributed coefficients only lunar Fig. loose We than to (1972); and Lunar In general, (PET), coherency equilibrium 11. concluded of production 68415 experiments of surface find regolith breccias. provided state. 61175 the GLASS Comparison the and et to coherence but .10 no for areal al., exposure and whereas materials. areal Planetary are 10 MAXIMUM simple Other glass all are however, populations density 1970; indicated. (PET), 61156 that Ds/ and are do densities in of polymict age, populations Only not DP relationship but CRYSTALLINE 62295 .15 these loose highest Institute Soderblom, coefficients greater are physical but 15 rock necessarily is Also their the crystalline have the same. "crystalline" populations sand is the exceeds highest properties, areal .20 AREAL shown G. breccias a • been crater than 20 crater crystalline Provided for properties NEUKUM with density (Gault, between mean the densities (1970). 1970; are investigated. various densities rocks Regarding the density or similar density saturation .30 with DENSITY coefficients a rocks are et by limiting 1970) Oberbeck combination highest lunar 30 are areal al. seem the rock of in only plotted. values coefficients .40 observed coefficients NASA For very rocks. (denoted the AREAL percent or SATURATION approachable the density (metaclastic) 40 to frequency observed approaching comparison, moderate rocks. Note similar have higher and .50 of These Astrophysics COEFFICIENTS may values both. 50 DENSITY the values Quaide, "Regolith" for .60 lower be differences are to For are areal The to densities systematic defined °lo date range .70 considered the coefficients intergranular 62295 much with nearly (GAULT, areal example, FREQUENCY the for (MORRISON maximum .80.901.0 Data COEFFICIENT density et on LIMITING lunar 1%8) RANGE by because of populations tough al, various may equilibrium density lower in in differ- System Gault the same. Morrison 1972) terms for Fig. regolith be and 1970) also values rocks inter- than den- 11). co- for of in 1973LPSC....4.3255N I I These that ballistic crater be crater frequency sity starting such equilibrium gests This rocks rounding size for Acknowledgment-The at Gault Chapman Bloch yields equilibrium exposure consistent diameter limit A= require Criteria Conf., crater Smithsonian the due Crater Counts Four The Our © crater paper distributions. 0.15 for microcraters D. M. Lunar target is equilibrium, Lunar size for low size satisfied Geochim. simulations, to E. R., results at wide with separate C. sedimentation surfaces and criteria ratios constitutes (equivalent and the age, (1970) populations R., different Fechtig present frequencies distribution Science densities obliteration with on after and materials. has implications. state. Astrophys. the Pollack range mass cumulative four rock confirm Planetary no Saturation been Cosmochim. all our production passing H., to discussions. Institute, of Some and are (4) greater Lunar not research removal J. of glass four exposure Gentner distinguish properties, in measurements. varying achieved, B., to the the Observ. destroyed The areal are evolve particularly loose are: fully Radio on that differences Institute and Science and 14% meteoroid criteria through equilibrium erosional surfaces which than Crater the Acta, reported higher lunar W., (1) Sagan density destruction may equilibrium understood. state Sci. Spec. materials exposure geometry in saturation) most Neukum absolute 4.5 is (3) Institute Suppl. between or populations • 5, terms operated C. by indicate rocks. and here CONCLUSIONS density Rep. a Provided and flux there an 273-291. REFERENCES have a (1%8) at effective state in coefficients transition the combination extended 2, crater G., was the the conditions 268. in reach were Contribution of are geometry Vol. crater exists by The of yielded superposition An the by and of done production These equilibrium. cumulative for largest crater shape of on by explained USRA the superposition analysis a 3, density, early Schneider mechanisms equilibrium unambiguously craters lunar the application surface, populations while pp. densities, a stage. for - surfaces in of minimum NASA differences reliable solar 2639-2652. 2 under rocks No. on impact of of excess the the slope on NE= the E. by and both. the size first 150. system. Astrophysics i.e., distributions Only NASA of (1971a) Mariner diameters lunar (2) cratering the for studied. crater statistics author for of same is A· frequency of equilibrium areal individual MIT in evidence These a populations the the fact the may contract the Proc. crater Meteorite constant shown equilibrium. D-;/. rocks 4 Press. was density densities rock dominant cumulative photography on theoretical analytical that be Data Second measured, different a For for the obliteration observed Visiting NSR demonstrates for events. attributed distributions to suggest impact erosion lunar System cumulative production crater spall-to-pit coefficient extensive from be 09-051-001. Lunar at process This Scientist of surface: craters, model crater larger views lower in Mars. den- may sug- that two and 3275 Sci. an in to is

1973LPSC....4.3255N

Neukum Neukum

Oberbeck Oberbeck

3276 3276

Soderblom Soderblom

Walker Walker

Marcus Marcus

Lunar Lunar

Shoemaker Shoemaker

Horz Horz

Morrison Morrison

Schnelder Schnelder

Horz Horz

McKay McKay

Gault Gault

Hartung Hartung

Marcus Marcus

Gault Gault

Marcus Marcus

Shoemaker Shoemaker

gamon. gamon.

Lunar Lunar

of of

under under

Proc. Proc.

Press. Press.

The The

75, 75,

75, 75, Observations Observations

distribution distribution

Proc. Proc.

chemical chemical

460-472. 460-472.

samples. samples.

Icarus Icarus

Lunar Lunar

craters craters

microcrater microcrater

Geophys. Geophys.

Amer. Amer.

Third Third

165-177. 165-177.

D. D.

Third Third

Heidelberg. Heidelberg.

H., H.,

F., F.,

4977-4984. 4977-4984.

pp. pp.

F., F.,

D. D.

Sample Sample

Lunar Lunar

Apollo Apollo

A. A.

A. A. Lunar Lunar

D. D.

E. E.

Lunar Lunar

Third Third

meteoroid meteoroid

craters craters

G. G.

Carrier Carrier

J. J.

(editor (editor

G., G.,

Sci. Sci.

E., E.,

Goddard Goddard

9, 9,

E. E.

Hartung Hartung

formed formed

2655-2661. 2655-2661.

D. D.

V. V.

E., E.,

H. H.

L. L.

H. H.

S. S.

H. H.

NASA-SP. NASA-SP.

B., B.,

E. E.

description. description.

and and

E. E.

(1971) (1971)

446-465. 446-465.

Res. Res.

(1973) (1973)

Horz Horz

Schneider Schneider

A., A.,

R. R.

Science Science

Conf., Conf.,

A. A.

(1970) (1970)

statistics statistics

of of

Storzer Storzer

Lunar Lunar

(1966) (1966)

(1964) (1964)

M., M.,

Preliminary Preliminary

M., M.,

Sci. Sci.

and and

(1%7) (1%7)

Horz Horz

11 11

Dietzel Dietzel

of of

and and

C. C.

W. W.

(1970) (1970)

McKay McKay

76, 76,

74, 74,

impacting impacting

in in

Lunar Lunar

Untersuchungen Untersuchungen

Batson Batson

F., F.,

J. J.

E. E.

Hait Hait

Conf., Conf.,

Conf, Conf,

the the

and and

Planetary Planetary

J. J.

Displaced Displaced

D., D.,

dense dense

Quaide Quaide

Geochim. Geochim.

exposure exposure

6081-6119. 6081-6119.

Microcraters Microcraters

5770-5798. 5770-5798.

Comparison Comparison

A A

B., B.,

F., F.,

Sci. Sci.

N., N.,

Arceneaux), Arceneaux),

and and

Statistics Statistics

Institute, Institute,

D., D.,

In In

A A

Young Young

lunar lunar

and and

E., E.,

H. H.

stochastic stochastic

solar solar

M. M.

Science Science

Sci. Sci.

and and

D. D.

Geochim. Geochim.

model model

Geochim. Geochim.

and and

press. press.

R. R.

Conf., Conf.,

and and

Hartung Hartung

(1971) (1971)

Examination Examination

crystalline crystalline

Mehl Mehl

H., H.,

bodies. bodies.

solar solar

S., S.,

W. W.

M., M.,

Conf, Conf,

Gault Gault

wind wind

regolith regolith

Gault Gault

mass, mass,

Waters Waters

Institute Institute

ages ages

J. J.

Fechtig Fechtig

Cosmochim. Cosmochim.

Swann Swann

Moore Moore

Houston. Houston.

L. L.

for for

of of

179, 179,

W., W.,

Geochim. Geochim.

Holt Holt

A., A.,

flare flare

On On

of of

in in

model model

pp. pp.

(1968) (1968)

bombardment. bombardment.

J.B. J.B.

iiber iiber

impact impact

Cosmochim. Cosmochim.

lunar lunar

Geochim. Geochim.

derived derived

Icarus Icarus

D. D.

equilibrium equilibrium

depth, depth,

the the

Duke Duke

Storzer Storzer

lunar lunar

23-34. 23-34.

H. H.

rocks. rocks.

and and

A. A.

particle particle

G. G.

22-23. 22-23.

H. H.

H.J., H.J.,

E. E.

Team Team

Einschlagskrater Einschlagskrater

• •

development development

G. G.

(1972) (1972)

impact impact

of of

E., E.,

C. C.

Genetic Genetic

A., A.,

(1972) (1972)

Provided Provided

(1971) (1971)

the the

C. C.

samples. samples.

7, 7,

crater crater

Cosmochim. Cosmochim.

diameter, diameter,

from from

the the

Acta, Acta,

NEUKUM NEUKUM

(1970) (1970)

Morris Morris

D., D.,

The The

and and

Schleicher Schleicher

Cosmochim. Cosmochim.

M., M.,

233-243. 233-243.

Claitors. Claitors.

(1972) (1972)

tracks. tracks.

earth earth

Effects Effects

formation formation

Acta, Acta,

erosion erosion

size size

Wagner Wagner

Lunar Lunar

Exposure Exposure

Micrometeorite Micrometeorite

crater crater

Nagle Nagle

Moon Moon

Heiken Heiken

implications implications

accumulation accumulation

Suppl. Suppl.

Earth Earth

Origin Origin

E. E.

Proc. Proc.

by by

distributions distributions

The The

from from

In In

of of

and and

Suppl. Suppl.

et et

C., C.,

of of

the the

J. J.

to to applied

statistics and and statistics

microcraters microcraters

Acta, Acta,

the the

D. D.

6, 6,

The The

Planet. Planet.

al. al.

G. G.

3, 3,

Apollo Apollo

auf auf

G. G.

microcratering microcratering

G., G., of of

Rennilson Rennilson

effects effects

28th 28th

and and

Acta, Acta,

the the

32-44. 32-44.

ages ages

L., L.,

NASA NASA

Vol. Vol.

crater crater

A., A.,

3, 3,

H. H.

Apollo Apollo

the the

dem dem

and and

of of

Suppl. Suppl.

survival survival

television television

Vol. Vol.

Schaber Schaber

Annual Annual

Fechtig Fechtig

(1972) (1972)

on on

Suppl. Suppl.

Sci. Sci.

of of

lunar lunar

16 16

3, 3,

lunar lunar

craters craters

of of

for for

Fryxell Fryxell

Mond. Mond.

the the

population population

Astrophysics Astrophysics

pp. pp.

3, 3,

Apollo Apollo

the the

lunar lunar

15 15

J. J.

oblique oblique

Lett. Lett.

and and

lunar lunar

3, 3,

lunar lunar

pp. pp.

solar solar

regolith regolith

Microcraters Microcraters

J., J.,

regolith regolith

Lunar Lunar

of of

1, 1,

Mtg. Mtg.

2793-2810. 2793-2810.

R. R.

lunar lunar

Vol. Vol.

H., H.,

on on

Doctor's Doctor's

on on

2713-2734. 2713-2734.

camera camera

2735-2753. 2735-2753.

samples: samples: Vol. Vol.

R. R.

and and

interplanetary interplanetary

lunar lunar

12, 12,

L., L.,

craters. craters.

15 15

flare flare

surface. surface.

the the

and and

(1972) (1972)

Electron Electron

lunar lunar

trajectories trajectories

3, 3,

on on

Whitaker Whitaker

Samples, Samples,

surface surface

59-66. 59-66.

3, 3,

samples samples

Sutton Sutton

of of

thickness thickness

pp. pp.

lunar lunar

craters, craters,

pp. pp.

tracks. tracks.

Bloch Bloch

the the

Data Data

on on

Tranquillity Tranquillity

thesis, thesis,

Petrographic Petrographic

rock rock

Apollo Apollo

MIT MIT

J. J.

2767-2791. 2767-2791.

J. J.

2399-2412. 2399-2412.

moon moon

on on

MIT MIT

Surveyor Surveyor

R. R.

surface. surface.

Geophys. Geophys.

Microsc. Microsc.

exposed exposed

System System

by by

M. M.

pp. pp.

lunar lunar

E. E.

Proc. Proc.

2. 2.

Press. Press. surfaces. surfaces.

1. 1.

L., L.,

dust. dust.

for for

University University

variations. variations.

Press. Press.

16 16

with with

means means

R. R.

Icarus Icarus

A. A.

415-419, 415-419,

Dahlem Dahlem

impact impact

special special

rocks. rocks.

(1972) (1972)

(1969) (1969)

Third Third

Proc. Proc.

Base. Base.

MIT MIT

7. 7.

time time

Per-

Soc. Soc.

Res. Res.

to to

and and

of of

5, 5,

3, 3,

J. J.

J. J. a a