1978LPSC....9.2857S three three appear of deposits excavated thermal nature unmodified small-size of ejected and account in observed longer less time nution. Abstract- rial the term crater the possible of sorting large The The ISR the than in in thermal thermal © crater crater record surface residence certain areas certain Orbital of to The materials. Lunar the formation lunar displays for Apollo following those night-time thermal data out these ejecta correlate debris, record The implications block-size radii last radii the upper Lunar of craters of that infrared and record Apollo concentrated mechanism, ejecta observed degradation time block the as from the from features which Second, 17 implications infrared of and Planetary with a are portions smallest contains information contains surrounding discussion and (D Infrared within result distributions the sizes large 17 the deposits thermal NASA-Johnson Planetary of cooler will smooth-surfaced > Scanning may of thermal rim, interactions and ejecta crater 3 pristine typically of Proc. which the be size km) these portions Institute raises secondary than both of observations smaller indicate is (Mendell, transient Scanning Lunar on rim. mare fraction. record Institute, typically first in the emplacement. signatures. is Printed around Infrared the smaller greater for observations interesting predicted contrast the WENDELL Copernican-age PETER Planet. Local between plains. lunar than Space surrounding concentrates • of in INTRODUCTION craters crater units impact gradual about small Fourth, exhibit Provided of the 3303 Sci. than Radiometer shock the thermal Radiometer impacting 1976b This United to Center, First, soil H. from selected on ejecta Conf believed 2857 implications prior terrestrial and NASA 30 what moon. the uniform MENDELL of the thermal pressures SCHULTZ large States (see cm 9th gravity mare ). primary-crater removal anomalies ray and ejecta by to further Houston, lunar might debris, cratering and (1978), The presence ejection, the Road on experiment systems impact to of Mendell, craters. impact surfaces. Of interpretations craters. night-time America signature that scaling represent (ISR) NASA for observations over comminute p. be present 1, reduce emplacement particular 2857~2883. occur craters the craters of ejecta Texas typically expected Houston, thereby a Four relations, process or thermal non-blocky craters. The Astrophysics ejecta provided larger revealed implies 1976a). within solidified temperatures the emplacement absence 77058 generate analysis characteristically mechanisms debris lack original resulting from fragmentation fraction Texas and interest that certain accounts by and on that We contrasts thermal surface Previous and, impact a simply a the consideration the of 77058 possible the size-distribution Data high-resolution examines greater interpretations in of comparable then ejecta third, surface dynamics. blocky are greater is for ejecta dynamics the enhancements extends melt. extrapolating System the proposed most and non-blocky fraction crater by may examine facies analyses of deposits Beyond commi- night- mate- locally long- ejecta out of what result to and and the of of or of to of to 1978LPSC....9.2857S 2858 wall surface face ever, dary the view, terrain. hancement, bright-rayed 1962; can more solar crater are Infrared Olbers the ters processes exhibit less ter nitude General ern contrast, edge ciated craters regions mal mal correspond nm mary Pre-Apollo Earth-based On Figure Earth-based radii cooler higher easily continuous obvious quadrant contours zones. © and enhancements area crater received illumination of the slowly crater and a closer Lunar chains with (Mendell, little A, and during far resolution These the trends Scanning floor from high for a la associated be Shorthill and than resolution from cluster chains. a to large and under or continuous as temperature examination illustrates than craters, correlated lack smaller exhibit diffuse displays measurements zones. residual lunar the particularly the observations THERMAL Kepler. its thermal previously radar ejecta Planetary their a .thermal and secondary 1976a) iegand surfaces fine-grained secondary major observed lower Radiometer that of crater If corresponding and with asymmetric eclipses. ray particles. surroundings. which Bright images the Lunar reveals hot deposit, thermal surface an with corresponds ejecta anomalies Saari, Institute impact. illumination, patch variations and large SIGNATURES thermal (Figs. rim, enhancement. spots earth-based recorded P. good remained thermal rays of diffuse Orbiter craters, craters at the H. generally The permitted 1969) deposit. impact temperatures exhibit the levels and increased the 3.8 occurs SCHULTZ 2b extensions. Figure • bright are coverage, maps strongest to Provided were and continuous with moon bright cm patches, from and to revealed signatures photograph are not large close craters but OF significantly thermal telescopic in owing A were crater 3), 3 17 and wavelengths generated overall delineation Between generally interpreted thermally smooth-surfaced LARGE shows this earth-based higher the (notably few filamentary km by blocks, most W. to contrast The secondary are including limited (Mendell, the resolution interior, numerous southeastern to MENDELL the small on enhancements and from temperatures that inner generally NASA individual resolution the LUNAR (Fig. view one nominal the from absent whether warmer enhanced Shorthill discontinuous within was of ( by larger as the to <0.5 crater rim views, lunar Astrophysics dark rays. 2), of crater rsacu, Copernicus, Aristarchus, major 1976b). blocky ISR Zisk thermal 10 CRATERS nearly typically Apollo in Aristarchus region patches the restricted one km level secondary orbital quadrant than relative halo derived arc The the surface. radius data et and comparable et is clusters, but strong geologic diameter) crater al., an regions Several confirmed. seconds al. middle corresponding of ISR in contrasts the ray in the are associated Data ejecta views near order and the (1974) the 1960; radiative from several to surrounding patterns The and thermal experiment. strong overlain radius craters under and System southeast- the three units and maria. large the that (Fig. fields deposits of to isolated the is Sinton, Apollo on closely secon- crater How- areas outer outer mare mag- asso- ther- ther- with cool high cra- sur- cra- and and pri- en- the are lb) on of In to 1978LPSC....9.2857S
@ r = ""I=
i:l-= -"'d ....= 0..., ""I g: .... .-+ ...."'= s· ...... ::t' 1:1,>..., .... (1) = 0. • g. "'d V, ""I (1) 0 1:1,> ...i:l- .-+ i:l- o· ;;' V, .... 0 =- -2" z ...,1:1,> > ...,(") rJl 1:1,> .-+ > ...,(1) > V, "'....""I 0 'C=- n..."' "' t::I (b) .... (a) rJl halo, and bright fila- Fig. I .(a) Earth-based telescopic view of Aristarchus under high solar illumination showing bright crater interior, dark "'.... (40 km in diameter) under low angle (15°) of illumination revealing flat mentary ray pattern. (b) Lunar Orbiter view of Aristarchus N LO-IV-150-H3. 00 s crater floor, terraced wall, subdued dune-like ejecta deposits, secondary craters, and ray patterns. v-, l,C) 1978LPSC....9.2857S 2860 The crater time temperature unit and with crater exhibit Profiles © highlands. characteristics. halo the temperatures surfaces around exhibit Fig. temperature photograph Lunar radius wall not exception of 2. of and only large and Contour enhanced Aristarchus display contrast from the reduce Planetary of residual contrasts. residual thermal Aristarchus the local on maps of The with the rim, the backscatter corresponds temperatures, to thermal of same Institute Beyond temperatures near IR southeastern the crater night-time P.H. beyond region. radial correlation cool enhancements, mare approximately SCHULTZ • floor to around large Provided (a) halo. which surface 96°K. from values Contour exceed annulus much quadrant. and Temperatures occurs temperatures Although Aristarchus the Aristarchus by the W. at 3 cooler crater the surrounding interval surface strongest the 128°K, MENDELL for NASA break-in-slope floor The radii other than is superposed returns are of representing extends 3°K Astrophysics and from continuous rapidly Aristarchus which the large shown and terraced the to crater correspond on the approximately crater craters decrease the Lunar of in typically base Data wall ejecta a wall nominal Fig. the rim, nearly contour in Orbiter regions System to crater along mare 4. lacks and the mare col- deposits Night- 33°K mare floor one rim the 1978LPSC....9.2857S but ter in Procellarum same with region ridges. consistent Comparison temperatures radii also stages do deposits. lapse spond, represent, certain local © surrounding not little Lunar from pits, return of time, in generally and Although some temperature mare secondary the large in and of general, the become Mare to crater cases, Planetary the emplacements. craters, correspond Aristarchus. tures the typical secondary Orbital radial to the Imbrium thermal rim. indicating locally wrinkle crater commonplace variation, block Institute mare infrared to Beyond craters thermal lower thermal size (b) ridges, signature Temperature systems, far greater surface distribution Closer • clearly observations temperatures. which removed Provided the and enhancements. decay number and view dominate in thermally bland is of isolated is one 3°K the on of characteristic resemble by of of from contrasts of case the Surface the thermal four large-size surrounding lunar warmer the surface, Bright a NASA primary a overall crater craters different major temperatures signatures mare typically ejecta blocks. than larger Astrophysics formed ejecta region, crater out impact craters, surfaces surfaces ray the residual to craters population, prior of deposits can are more thermally outer believed crater. to be Data tempera- and within of the reveals than corre- ejecta correlated variations they Oceanus System last wrinkle to At 3 bland a 2861 cra- era- the the 1978LPSC....9.2857S
2862
These ter
the
the
Olbers
general,
phy southeastern
plains material formed
Localized
The
radius
crater
crater
©
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deposits
Fig.
er
shown ejecta
enhancement radiometer
greater Lunar
thermal
A
V
on
the
3.
mosaic.
extends
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interior
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the
Detail
draped
and
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that
strong
Fig.
quadrant.
extensions
system.
(arrow
plains
(Fig.
region
map
Planetary
(see
crater
Bar
of
7a
these
to
by
and
thermal
that
thermal
scale
Fig.
B)
a
6)
and
Large
of
materials
greater
of
rim
identified
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and
exhibits
local
61:)).
Aristarchus
Comparison
containing
corresponds
the
Institute
can
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Aristarchus
night-time
(fig.
block-strewn
Arrow
southwest
P.
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distance
0.5
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by
exhibit
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5).
of
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SCHULTZ
•
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R
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Provided
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to
with
2
and associated
than
D
km,
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attributed
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lowest
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and
and
surfaces
high-resolution
5°K
the
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Olbers
R
by
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local
W. shown
deposits
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(arrow
approximate
the
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temperature
units
thermal
contour
MENDELL
the
with
NASA
(Fig.
increases
to
in
A
(see
A)
to
superimposed
Fig.
the
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in
(discussed
region
large
occur
dune-like
7).
Fig.
Astrophysics
contour
of
direct
7b.
presence
spatial
differences
Lunar
Small
Copernicus
and
6a).
near
of
in
craters
crater
inner
also
temperatures
contrast
Similar
resolution
on
dune-like
of
Orbiter
(
below).
forms
of
<0.5
lacks
Lunar
Aristarchus
ejecta
from
Data
rim.
is
impact
dune-like
restricted
thermal
and
km)
to
region
Orbit-
of
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System
facies
containing
photogra-
Thus,
the
the
Kepler.
melt
craters
in
non-
and
the
to
in
in 1978LPSC....9.2857S the northeast radius formed Olbers associated est termini material. blocky 104 1976; As (see - :::, - L&.I cc: 0.... - L&.I L&.I cc cc: ._. D Figure in °Kand residual exception 128 100 108 120 116 124 132 104 112 Schultz, 96 92 tion; occur comparable out Fig. temperatures the Guest, © from 0 A, (at \ and \ in Lunar ..., .... ,-... = = u _, = cc = = to 4. 8 The solid case side within with which 106° the 10 three superposes Thermal the u ,-...... , 3: cc _, = = cc _, temperatures. have 20 1972, IA I 1973). line, smooth-surfaced and of m but of to ejecta surrounding = = - V> = = z: u K the crater rapidly crater the resolution) Aristarchus, is the been ..... ,-... cc u f\ contours Planetary in .\ generally profiles plains 1976; in u ..,, ..... SSW 40 2A deposits Similar mare I northwest radii rim, highland decrease Orbital the interpreted direction; radial surfaces Guest, units from Institute The the extend night-time 60 to 3R I DISTANCE decay smooth-surfaced units infrared ejecta the from .... the to terrain plains the are ejecta terrain and quadrant. at Aristarchus. southeast and 1973). crater the beyond occur 4A BO rapidly crater much as • believed three I obsl!rvations around dotted Provided crater (crater units pools FROM thermal displays facies ( adjacent kilometers) greater crater interior rim along before 100 the SR line interior away I The Broken commonly CRATER radii) of similar typically to exhibit by radii. break-in-slope in ejecta ejected of distances. matching map a the reflect northwest the SSE to from (floor generally lunar 120 to 6R line I CENTER NASA western northern crater size on exhibit direction. considerable indicates deposits. craters the the display uniform impact and Locally a craters 140 exterior. 7R photograph I Astrophysics competent rim. even uniform quadrant wall) Oceanus Residual profile crater of levels high melt fractures Beyond The the 160 and temperature, BR Ejecta I exhibits variation temperatures temperatures between in (Schultz, crater rim night-time blocky SW larger exhibits Data nature Procellarum. of deposits 180 9A and one I direc- where the the System one wall/rim craters on lobate ejecta crater of crater 1972, high- local with 200 lOR 2863 the the the I 1978LPSC....9.2857S 2864 as and where these Schultz Hawke thermal crater-associated patches deposit Moreover, quently Aristarchus ment alies Secondary The Although are © striated Temperature tance Fig. temperature are history pools Lunar similar the smooth-surfaced and (1972, and of a contours 5. comparatively similar corresponds high primary craters the Thermal and ejecta is Head represent a secondary was units ridge. 0.7 1976) I- a:: LLJ topographic LLJ g§ LLJ residual contrasts Planetary contrast phenomenon 10 and (not more km facies (1977) profiles crater around to The noted the an lower solidified restricted craters are complex. is pool temperatures sparse. Institute and equivalent of smooth-surfaced pool confirmed referenced rim indicated the that elevation P.H. Aristarchus, than is northwest intersects may northwest believed craters around Figure such SCHULTZ impact • to radius the Provided on have to secondaries) this of pools the center. that the Olbers elevation King derived Aristarchus 9 of to the and melt. a occurred ordinate observation of compares outermost depression. correspond be Olbers by unit are w. pronounced Olbers A, and the part from The Kepler, MENDELL most clearly northwest but Tycho. NASA thermal at the of A continuous A close the are do Aristarchus, the occurs common area and and supports to not In Astrophysics superposes number abundant, thermal ejecta a of Copernicus. correlation a anomalies always likewise smooth-surfaced of continuous more in contour. Aristarchus. and a facies this occur density topographic high but extensive Data the concluded thermal most interpretation. Radial Maximum on contours. the of at between southeast hummocky System crater Olbers the of extensive emplace- dis- Conse- impact anom- study, plains maria low. that the A, of 1978LPSC....9.2857S (a) (b) crater than and Fig. Similar surface enhancement not © ' Lunar ,:. contain appear 6. 15°K ' rim . .., dune-like (solidified High-resolution I to contrast and smooth-surface to " this . •" associated drape Planetary region ' form impact with Orbital portions (b) adjacent (see view with melt) to Institute does units 0.5 infrared Fig. (bar region of having not km. regions 3, (see the scale arrow exhibit • Lunar observations in Fig. only dune-like Provided (a). Fig. A) 3, a 0.5 Orbiter pronounced Smooth-surfaced arrow thin where 6a km) is topography. by regolith veneer. of believed B V-196-H3. they the of lunar for dune-like thermal NASA are location). craters concentrated to units Lunar be Astrophysics signature form Bar associated extend Pronounced Orbiter scale exhibiting in from and corresponds depressions V-196-H2. with Data also near thermal more solid does System the 2865 1978LPSC....9.2857S 2866 © Lunar warmer this subdued striated Fig. temperatures region 7. and Comparison and than topography Planetary are blocky are regions more only ejecta zone Institute of of than shown 3 ° inner southwestern K identified deposits. 9°K warmer P. in ejecta • H. cooler Figs. Provided SCHULTZ Bar scale by than facies 6b arrow inner than thermally and by and of the corresponds C ejecta 7b. the Aristarchus. in area W. Fig. (b) NASA uniform MENDELL deposits shown (LO-V-197-H3) 3. Temperatures to Astrophysics 0.5 region (a) in (Fig. Fig. km. (LO-V-197-Hl) 3, of 6a outer arrow shows but associated Data are continuous D) System relatively 3°-6°K where shows with 1978LPSC....9.2857S hibit 3. dary clear. Nevertheless, The Fig. trasts with primary) with 3.5 5 The crater crater contribution 9 the a same on Fig. west a contours draping high hard-rock craters The (6°K © temperature distinction poorly by the Lunar distance 8. of temperatures near general radii impact low most radii the The by < have also surface. rim defined and rim Fig. a AT the 45 of from obvious thermal similar side from 3°K between km and to origin Planetary probably the < crater contrast 9 of diameter associated The the 9°K) intervals; correlate the maximum. confirms crater unit the Orbital Olbers signatures secondaries enhanced may maximum rim rim center or a because Institute greater occur. secondary crater A, rim. a infrared with contours with and to be blocky which of the a of temperatures a All Olbers desirable the Aristarchus. reveals well-defined pronounced • Consequently, than Aristarchus. anomalies is observations paucity IV-174-H2. impacted occur surface within anomalies Provided smooth-surfaced associated crater A 6°K occurs that in the exposed but on associated Locally of clusters smooth-surfaced and increases by crater the of of relatively in maximum thermal exhibit would the The lunar with highlands later higher edge by high separating unit NASA are number secondary or with craters of relatively primary from not temperatures suggest result a chains, a anomalies contrast weak notable Astrophysics much terrain the shown. near unit. less ridge of in a impacts. larger the crater anomalies This and but thinly seven thermal than low interpretive Lunar deficiency (AT may occur distributions exhibits isolated crater. unit (secondary veneered Data thermal 2/km Thermal is indicate crater Orbiter > occurs north- not anomalies The 9°K) System the increase 2 always secon- within within radii. bias. con- 2867 ex- or in 1978LPSC....9.2857S 2868 with these bright cause nmle, however, anomalies, compares Second, tion than however, spond impressions. signature rior .., 0 ,...... Figure 6 4 5 7,------© of on range. approximately three ter tion near Fig. anomalies 0 0 Lunar they halo. to Aristarchus. radius the the 10 9. crater the the increases single 20 are and Number Comparison surface. permits seven Three largest from thermal contribution radii Planetary smaller correspond primary-crater craters the 40 2R crater density from craters with 2 This crater Two remnant comparison generally NUMBER BEYOND km signature radii the 60 than Institute of crater rather of is rim. in general rim. from and nearly thermal the P. largely to DISTANCE diameter ejecta TWO Large the 80 H. 4R temperatures clusters Small probably DENSITY correspond thermal size than should single SCHULTZ • of system CRATER anomalies trends and 5 anomalies Provided an anomalies 100 in crater km multiple the reflect of exhibit this anticipated craters (from OF be map and in aria! secondary are RADII resolution. 120 6R on size proportional region by (AT THERMAL to diameter the W. (0°K at and dispersion crater shown. the the isolated an and crater balance FROM > MENDELL craters, a and 140 maria < NASA 12°) underestimated photography given but effect AT center) craters. thermal ARISTARCUS are ANOMALIES are between First, At beyond remains with < craters 160 Astrophysics BR relatively thereby diameter 6°K) to from not a clusters. distance. the given the The approximately impacting signature exhibit shown 180 exhibiting the lower shows block-size constant maximum more confirming crater L:!,. l:!,.T=--15°K temperature l:!,. generally resolution Data Craters a 200 lOR T> T=-- concentra- in than energy that pronounced and beyond Fig. System 12° 9° a diameter, a 210 cra- distribu- th~ K thermal most diffuse, by smaller further K 10 corre- visual limit. inte- but be- 12R 220 of 1978LPSC....9.2857S 4.5 croached attain km facies. (and certainly km in LA,J - :?: ...... :::::, - 0:: L.U 0.. 0:: < L.U 0 pre-Aristarchus) ters are Fig. temperatures © Also diameter, in cluster Lunar on 125• 120 115• 105- 100• 110- represent 10. by diameter vast the not Correlation mare maria majority members; and included is Planetary units. south and endogenic as 0e a of crater Orbital between pre-mare high closed e0e00 .5 I appear secondary •• of The •• : in (:) Aristarchus. 00 Institute e Fig. as • circles 0Gl (!) infrared CRATER confirms survival peak 0 features. the (!) to • 10 craters • C!l0Gl crater 1.0 I be temperatures represent interior (!) e3 K) thermal NASA ® 2.0 0Gl The (j craters and I facies It km) temperatues should KM of 0 Astrophysics crater ® • third, • • • Two • irregular contrast • the below -- clearly be diameter 2.5 are Aristarchus approximately I noted of 102°K. craters approximately in has pits Data -- that for a that pre-mare been that cra- 3.0 System the ejecta most 2869 en- 5.2 1978LPSC....9.2857S 2870 the ejecta the ing contrast surfaces temperature A the temperature where rim, Comparison exist extensive This ray lating nearby 1972, near The Figure typical from hummocky system © temperatures ejecta for Aristarchus ~ 0 w a: :::, ';;: a: a.. w Fig. w km-diameter in I- 1976). Lunar dune-like observed blocks their 140 120 crater. 130 110 100 95 beyond this 0.5 with comparison 11. 11 bright-ray blanket -- suggest zone size and with km greater Comparision also decline particular as range ~ class. The continuous ______Planetary thermal large on topography to 7 generally the (Fig. small shows in the reduce that The peak than around general km system. continuous characterizes is as lunar 10). temperature primary crater, shown of the 70 contrast Institute the on that temperature thermal to __.. maria lacks ejecta mare The P. I fine-scale the I at ...... I I temperature Aristarchus. can I less I Although I H. I in in I the I approximately south I craters lunar to I I ~7KM~ crater blocks I l profiles SCHULTZ Fig. • of I / ejecta Aristarchus. be visible decreases than I facies / : . typical . I . Provided / strong I / craters . secondary . . / . . . compared . of f I 0.7KM 11. I ..,,'\ maria morphology / diameter Aristarchus. the is of pristine /', down \ facies. and mare \ on higher and . The . . . . slightly within central . ', . \ profile Lunar temperatures by \ in \ . the . \ . W. in \ earth-based \ levels. \ \ 7 to the \ \ 0.5 \ craters \.------~ Within this \ the with \ a MENDELL km-diameter The inner ' resolution (bright-rayed) I is the resolution NASA Profiles Orbiter thermal of higher to smaller general probably size isolated resolution rapid 1.0 a rim and a smaller Astrophysics are crater range crater element of telescopic than but IV signature the decline than typical vicinity photography the craters primary crater resembles merge photography thermal the radius and radii limits (0. of the surrounding of the 7 7 of isolated Data fresh of exhibits views km system resembles and with km from crater craters (see of temperature Aristarchus. character and System craters Masting the preserved diameter) does an show the Schultz, rim 0.7 reveals resolu- craters a crater undu- rang- mare peak rim. not the its of C 1978LPSC....9.2857S tion, elevated craters. cool these relatively three rim surface, 30 and exposed of instances wavelengths. that Summary anomalies 7 m 7 appear cm) exhibits rounding believed (1974) contrasts shorter enhanced whereas be behavior Superimposing cesses lation, larger rim. that posing The Thompson Infrared The pristine cm understood for obvious blocks the wavelengths low night-time which crater features © in blocks. accompanying Apollo thermal-infrared reported to the large but Although a Lunar wavelengths pronounced whereas Fig. blocks surface to dimension. residual but but correspond non-blocky numerous correlate bright of occur thermal mare Apollo thermal within indicate radii most a observations secondary 5 et (40 Consequently, average little and is Copernicus, low ISR shows 70 POSSIBLE by al. in residual in halo craters unexpectedly believed temperatures, from km) Planetary radar and likely temperatures cm 20 a portions this the 17 reflectivity with (1974) radar contours. experiment properties craters. signatures few radar ejecta and that m to impact should radar ISR thermal craters Orbital the found gradual deposit craters in of smooth-surfaced reflection thermal record accounts temperatures. crater IMPLICATIONS probably and thermal to reflection compared rim results this reflectivities Institute the of in deposit on Consequently, be infrared radar crater be numerous and discussion the Other at particular, and of surface. of low size Aristarchus lack correspond such erosion are of ray reveals produced result 70 lows. destroyed craters a for ejecta for contrasts to ejecta data 3.8 exhibits data • radar range. pristine formation. typically observations probably patches cm pronounced occurrences Provided halo results craters less Copernicus the cm from Thus, FOR at wavelengths. of Based that can penetrate deposits craters the pools facies fits 70 reflectivities than by occurs lower signatures. the thermal the extend surface there to EJECTA and at more be size cm extends the blanketed by blocks exhibit this less the of smaller conditions on The block-strewn infrared a representing the used provides extend with lunar secondary central ejecta of thermal crater of represent on is high latter beyond than the to efficiently NASA to since contours Aristarchus maximum Aristarchus an EMPLACEMENT or radar to to only craters a This strong This depths analysis at reflectivity blocks inferred surface 30 to three deposit pronounced radius rock and class investigate temperature. Astrophysics small a contrasts 70 about 0.5 in the unexpected cm reflection class potential exceptions. craters competent ejecta radar cm reveals thermal only surfaces. crater of between crater than but block in for blocks outer by structure paucity displays between and of one craters. wavelengths diameter. associated preservation smaller Winter (3.8 the blanket anomaly and exhibit larger the radii Olbers radii a Data size crater 70 maps clue limit recorded and close The behavior Thompson uppermost cm 10 units. Most of possibility in cm relatively Superim- less from observed System one from for 20 (1970), and several (5 blocks. 3.8 reveals and typical radius, locally of A crater corre- Local could radar than with km) cm- rays The pro- and sur- and 2871 the the the cm 30 by 70 of is 1978LPSC....9.2857S
2872
on
ter
whether increases
decrease
ties ties observations
than
deposition
ejecta-size in some
primary
distribution different ing
mechanisms
the
Mosting holds Ejecta tarchus
factor mon
m),
size
km),
from
impact,
tionally, provide by cylinders
In
In
The
©
the
an
3.
1.
2.
diameter
surface
of
and corresponding
(range),
crater
Lunar
distribution.
the
addition 30
general,
and
process
the
for
comparable
bris Near-rim
terrestrial Crater
and
increased
the Most
rim
fragmentation
of
maximum
approach
cm,
crater
or
and
empirical
a
C
Curran
with
from the
craters
maximum
ten
in may
ejecta
and
of
(within
reasonable of
in
distribution.
not
(3.8
diameter
explosions
secondary
produced
hard-rock
are as they
secondary
also
lunar
rays
(Gault
ejected
sizes
associated
smaller
the
to
Planetary
the
diameter,
and
reflect
these
the
inferred
km
(between
considered
number
et ejecta
facies
from
impact
Meaningful
block
may
must
140
observed
crater
typically
20
size
relation
and
al.
distribution
of
secondary
in
block
processes
et
in
blocks
m
m.
than
diameter) differences
the
craters analog (1977)
a
form
and
by
Institute
range,
and
targets
with
be
terrestrial
cratering. size,
fragmentation,
al.,
of
centimeters
few First,
from
with
then
Factors
craters
interior,
of
a
0.5R-3R)
satisfied:
size
final
the
distributions
the
indicates
are
age.
P.H.
maximum
secondary
in 1963;
large
relatively
is
m
large however,
showed
ejecta
statistics
simple
also
to
impacting
the
craters
interaction
an
are
will more
surface).
is
to
•
crater
not
extrapolated
ejecta
are
SCHULTZ
the
Provided
of
owing
typically
impact
unlikely
nearly
in
Explosion
infrared
impact
exhibit
a Moore,
similar,
blocks
reduce
associated
two
emplacement
as
feature target
detail
ejecta (Moore,
cratering
that
ejecta
that the
may
diameter.
fine-grained
of
block
represents
impact
large
deposit.
other
in
to
and
by
ejecta
100
craters
ballistic
by
small-size
event
the
around
among
the
only
process. the
result
observations.
thereby
1971).
below.
properties.
erosion, deposition
low-velocity
W.
facies
the
as
craters
km not size
from
processes
maximum
fragment
block
maximum with
craters.
1971).
processes
MENDELL
will
NASA
60
1
The
(D
increases
For
in
%
in
displayed
increases
ejecta
only
ejecta
may
If
m,
exhibit
large
material.
smaller
With
diameter.
fragment.
large-size
indicating
further
the
debris
>
sizes
at
subsequent
the
much
Astrophysics
question
This
whereas
on
5
Both
a
shallow
result
For
crater
may
size
sizes
fraction
craters;
(500
km)
block
block
fragments
sufficient
(Oberbeck,
Moreover,
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213
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1977).
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a 1978LPSC....9.2857S conditions explosion the producing produced a asymptotic over gests In will results velocities maximum particle between explosion detailed Experiments m nearly strength range tions Velocities 1977). and projectiles. survived ejecta emplaced crater. impact tion ment 14 less they ment to hence, given If Impact The If general, in the m size impact the than the around seven near-rim that are friable on size diameter. size from around © Ballistic around thermally infrared the of velocity total diameter above sizes. mare empirical Lunar the predicted with 0.5-5 ballistic 0.3 approximately less craters by velocities event much primary-crater is a may block greater are orders same value the at a It 58 maria smaller 2 a energy m, with an particle surface 40 than a a Extrapolation velocities which and similar. ejecta is ejecta m m be maximum signatures breccias. 40 near in smaller A which 40 sizes km impact. cool of as interesting km-diameter should transport crater. diameter and of studies Planetary than produced small-size ejecta (Fig. hard km-diameter approximately 10 the km of the of than magnitude crater. 50% size arriving 5 seem inner size, excavated 50 Orbital Consequently, formation-then km is the cumulative 62 kmls crater 12), projectile 50% bedrock less laboratory provide As This m. size smaller ejecta of Thus, block 10% distributions of of mis Institute crater). cratering this at contradictory. ejecta ejecta ejecta At if crater lunar infrared then to the than projectiles to of within (Pohl distributions the is the crater and of result in transitional two note, fragmentation an size fragments the ejecta crater from further an than (85.5 the the size 60 Ries craters 35 facies primary-crater sizes (for depend size Figure • size Aristarchus-size observations between impacts et ejecta crater one order-of-magnitude ranges Provided event mis. mis will similar if in projectile however, the (Moore, both al., are should tons mass at basalt distribution produced increases, the ejecta by fragmentation crater of suggested suggest will a impact values 12 Ejecta mass should 1977). are radii on a Hartmann will craters from scaled velocity impact range TNT into fraction thermal 0.2-2 illustrates by direct projectiles of result be distributions of compared crater radius 1971). the will produce radius. that from lunar predicted basalt a that impacting by more ejecta at arriving buried Nevertheless, range the of depth larger NASA factor and is by m function be event might velocities the in occurs. craters 32 20 signatures from size the the the Fransden distribution (1978) and the between where a the extensive Owing explosion (Gault are pre-Schooner km, between indication m of Astrophysics 22 maximum the with and than maximum of block crater within (Post, ( be a 2 a similar above. range 40 17 burst around primary-crater ejecta shock m 10 Figure of corresponding same suggest too the hard km-diameter block-size km 5 less m below to to et sizes crater 1.4-14 (1967) of fragmentation km. rim, the in is than 1974; 0.14-1.4 around maximum the large al., 100 craters A weakened may shifts diameter) ejecta distribution than of equivalent rock not mass fragment 12 particle block Data are smaller same that 50% ground decrease ejecta 1963). II larger fragmenta- size also performed m contribute too for Wisotski, 170 generally chemical to targets). distribu- System deposits fraction and 2 a ranging size impact m blocks only- scaled of shows crater larger larger large, sizes. to frag- sizes mis. than frag- sug- or The size 2873 and and 140 size the km for an of of in if 1978LPSC....9.2857S 2874 craters observed impact of are and hummocky Ejecta © As the not Lunar this and data Fig. tent impact same interactions velocity in the complex crater volcanic differences 12. from and the same; and age Particle-size craters Planetary ejecta. same Gault or and dune-like bedrock; morphology physical :::> thus, ...J 0 0 > > 2 e:( IJ.J :::, :::, ...J f- 0 l- IJ.J IJ.J z UJ Q. a:: et Pre-Schooner target in exceed between 10 al. Institute similar distributions other data (1963). (Schultz, materials properties P. approximately CRATER from Shoemaker 0.028m H. thermal target factors suggests LABORAlORY • Particle-size II 1cm PARTICLE Provided SCHULTZ Frandsen CRATER is (basalt) for a 58 the 1972, materials should are of and signatures m-diameter lunar a DlAMETER the and by (1967). complex operative. distributions 0.89m Morris 10cm 1976; 1 the surface W. projectiles always km suggest SIZE NASA MENDELL Laboratory (1969). chemical Howard, in of at emplacement diameter, 28m be primary different of Astrophysics Im that the the which explosion :s ..... impact lunar 1974; ejecta same Surveyor 894m and IOm ejecta produced surface crater crater sequence. Data Oberbeck, secondary regardless size landing facies represents in System are distributions compe- them. from sites become Models craters of 1975), The the 1978LPSC....9.2857S of comminution primary-crater ited Schultz, sizes ejecta fragment craters greater ing, (Oberbeck, fragmentation cantly the ties fragment relatively tion ness, formation sion Computer-code delay able thereby region 1968) tation sion seconds craters, First-arriving reveal may interact where size ejecta. nution than documented thereby The An Thus, impact (v rim), but and time distribution in in not following (Orphal, 4 t, estimate involving within degree © of longer-term :::::: complexly time where but velocity crater ejection than multiple-body by Additionally, at implying undergo comminution 92 1976, 1972, for Lunar with suggesting represent a energy 40 both size short-term sizes large (10 ejecta 0.3R time simple the also 1975; mis a sized. between by two may of later seconds). radii) the 0.5 decreases primary-crater the and (e.g., probably a interacting pers. ejecta of results (approaching from arrival within velocities calculations impacts comminution at emplacement Oberbeck expended simple around considerable large distorted km-diameter flow crater model Morrison Planetary impacting be the the 2R process arriving In other processes and 1978), fragmentation singly comm.). rim such important by and from emplaced long-term impacts Orbital in first time field interacting dispersions mass power Consequently, and isolated dominates. radii into secondary a of is extensive from complex a delay Institute any ejecta with per and and approximately ejecta. fractured the of and of ejecta process and of ejecta the infrared per ejecta complex two of depends In explosion suggest interaction ejecta law, produce shallow-buried crater rim), the particle. resulting as Morrison not high ejecta time fragmentation power Oberbeck, secondary a last unit curtains addition, minutes). systems in sizes a small and During • process owing ejecta mean of craters that observations N only may produce A result Provided small ejection ejection in and basalt) interaction ejecta area targets secondary-crater that oc size in 40 simple impacted target law ejecta extrapolated interacting mask and Hartmann (D contribute d- within velocity part ejecta 40 interactions km-diameter during (1974). as of 50 arri.val of the distribution ( t at near-rim craters laboratory 0 steepens 1975). - < 6 seconds secondary a ejecta. impact by arrival produces m), velocities :::::: secondary-crater on greater velocities (typical or where of explosions arrival fragmentation long 0.5 result (e.g., the the 500 flow lunar the destroy the can and to is mass However, km) also NASA Such to ejecta primary a delay (1969) relatively craters m), ejecta total later stages where N at craters for from volcanic at of be conservative distances (Guest short of can altering experiments owing per a crater and but typically is impact the craters (v ejecta different the interactions a Astrophysics most and made ejected suggest wide the time times occur. 40 :::::: curtains relatively unit noted are also same angles. primary N are crater widely same ih relatively with 250 not long km-diameter number and ash), represents low the geologic oc and ejecta of range crater not whose by area from probably to possible lack of that blocks. scaled d only abrasion, m/s arrival that ejection expected further Murray, - estimate calculating primary-crater and A primary-crater crater simply the scaled as 1.2. spaced (Gault crater (ejecta Data small the suggest blocky of 10% interactions 10% represent at to of ejecta short-term graphically secondary Impacting maximum materials) range fragment fragmen- 2R particles for a times primary, System compar- growth, commi- forma- depos- disper- disper- veloci- signifi- craters crater. range. grind- et (more thick- ejecta in 1971; from large rims, large that may 2875 of al., the the of a 5 1978LPSC....9.2857S 2876 within dynamics sizes for acting deposit keting require Ejecta ta by Increased small-size events velocities blocky events. minution. comminution fragmented within 1974) et with ejecta crater where 1974) as the and approximately constant. near In The Two The al., size-distribution the subsequent final © where within increased an the Lunar and 1973) sorting size. suggest by preceding loosely debris the observed would relatively may ejecta processes further out First, atmosphere-free ejection of heavily fraction reflect This excavation ejecta Second, crater also vis Schultz to and the debris and increase requires might deposits. system be empirical compacted three that the relation theoretical input imply processes. as impact Planetary scaling around greater uniform discussion would (Post, comminuted retained may velocity of R ejection within of the and ejection 0 increase. crater · comminuted energy the that 6 that crater small-size (Schultz, . contribute event. indicates residence 1974). of More Gault generate secondary shock data Institute fraction temperatures ejection deposits environment, a near a near-rim within treatments. However, velocity P. radii generally large scaling is rim velocities H. Possible (Wisotski, secondary-crater (1978) precisely, Otherwise, pressure observed the 1972, v(x/R) craters SCHULTZ that from • have yet the crater time ejecta to of velocities Provided (Schultz craters. rim; at ejecta relation increased small-size with suggest centered smaller processes impact the 1976), the Nevertheless, mechanisms a of (time increase ( histories and in = g, increases any <0.5 it in finite 1977) the position increasing above thicknesses rim large Vt(;) the indicates by terrestrial W. and exists increase that ejecta from crater. seismically continuous size the km) on MENDELL as gravitational comminution debris (non-zero) primary-crater and associated Gault, impact with and, a -3 NASA well such extrapolating the ejecta, with between x certain and impact include sorting within scaling crater such that Increased at by explosion crater with uprange. as a Astrophysics modifying 1975), crater craters the implication, relation and induced the the thereby processes size to sorting crater a velocity size, with ejection same must acceleration; considerations crater size. within inferred discontinuous time power-law size. crater and ejecta. These ejection ejection craters large-size can size relative result this vertical producing within Such Data late-time of of observed Consequently, could that velocities larger nearly be greater radius (McGetchin ejection) possibilities small distribution Impacts System (Wisotski, expressed increased from velocities velocities increases an decay and position account sorting impact impact all ejecta (Post, inter- block R; blan- com- ejec- non- (lb) (la) k, and the the by Vt, of of a 1978LPSC....9.2857S with If decrease ejection constant strength, This reflects exhibit root manner, portional crater given crater begin sures crease increases should O'Keefe, Because where projectile scaling, mately When impact gravity Equation The From © crater scaling indicates engulf to size, Lunar radius. X1 impact vi preceding in be equal. velocity, scaling the velocities R Eq. prevent follow is peak strength is is however, = ejection to 1977). less radius expected. ex: size. probably the neglected, energy (1) the implies and rp a the (la), E 1 As Therefore, larger 113 shock rapidly that velocity, projectile somewhere and can power-law impact Planetary Ejection the · From material energy. (rp) 6 qualitative a • is the (see velocity required Consequently, be x crater first gravitational a that ratio 2 dictated to fraction pressures valid crater ratio understood Orbital = than the Gault velocity the approximation, Institute the target radius Fourth-root velocities rp with the of size attenuation preceding 2 at description between of , crater to -=--· does description size the infrared projectile the by flow the of and insufficient the excavate varies and represents and rp/R rp/R2 medium, the target scaled peak increases • forces same vf vf, projectile for near in radius velocities Provided Wedekind, _E R r 2 must observations ejection the excavation E physical considerations, = 1 as scaling, two = shock out rates size-also properties = is projectile (rp rim scaled influence a can the cube -- rP E eventually Eo.os33 (R) (R velocities (x2/R2) (x1/R1) the v? certain 1 2 to different 114 an as R2 and by /R /R ejection is position . 1 are 3 be size. pressures a velocities the )0.192 is terms increasing fraction 1 2 the energy Large-size root proportional of however, )3 position certain 1977). shown easily crater projectile 3 expected 3 lunar cube NASA radii mass (e.g., related the Consequently, and from from decrease energy velocities therefore, where craters derived velocity, shown root If crater with are Astrophysics explicitly. becomes are with (volume) fourth-root strength). indicates leaving the gravity impact to to assumed of closely impacts density to increasing peak increasing E be to to flow target energy from projectile becomes 113 Vt, larger zero be: comparable -is of the scaling craters of The shock with which that Data field related, the to with partial relationships. (Ahrens material crater. exhibits but (E directly ratio shock be crater excavation crater System crater 113 increasing and, relations. pressures increases size probably the this ), approxi- gravity Cube- which an of and pres- same for final with size. zero pro- in 2877 size and size the (2) (5) (4) (3) in- a a 1978LPSC....9.2857S 2878 or for ties Consequently, craters It size largely cence, the fewer of cleation size pressure from where history velocity different power-law these velocity), has ejected if velocities 6% at crater. fraction the 16% impact crater. the but impact namically Shockey should crater Figure As flaws velocities hypervelocity longer also fractional grown © is of distribution at earth the of ejecta crater flaws Lunar a ejection the thereby such depends produced For Figure at and craters. at controlling sites the should influence of growth (sediments) history be input scaled 13 then approximately 200 100 decelerated may the final decay to et the (basalts). cylindrical and scales will the noted crater size compares exceeding defined al. approx.imately ejected mis stress crater 13 most ejection velocity as total producing be Planetary reflect ejected on the The has positions impact ejection within is increases, of by impacts (1973) suggests the the within corresponds that a ejecta a factor. velocities been of hypervelocity duration, ejecta high-velocity radii. by very controlling also The volume stress maximum airborne the the applied crater the ejection increases the the volume. 200 velocities inherent Institute and 0.5 corresponds velocity (Gault will well within smaller will poor largest degree Moreover, that material projectile mass surface ejecta target P. m/s. amplitude km half Curran to growth H. represents be the behaved produce peak to most debris. representation velocities include excavation For SCHULTZ shock and factor; • and flaws as the ejected The its fragments of suggests greater a leaving at medium. ejecta fragment impacts Provided at ejected R very stress, final shock-induced ellipsoidal Heitowit, ejecta crater. impact the et 0 arrive a and the - to volume 6 in decreases. The pressure range , (i.e., al. smaller higher for and Fig. 16%. the the fraction small same at implicit radius. the the no for could by that from stress (1977) absolute diameter W. observed at The different velocities sizes. will velocity As material, 13 hemisphere relatively of the compaction, crack crater different closer (mass) Thus, MENDELL velocities fraction 1963; of position crater reveals for nearly and derived fragment NASA be greater the be At duration, relation probably For the Because note propagation fragmentation. a produced different. crater at subsequent size such and Ahrens somewhere scaled crater materials, leaving given of a growth exceeding targets Astrophysics ejecta 100 little 200 the that size that given within from the for of material projectile/target defined between velocities sizes crater this up progressive is and mis fractures leaves the ranges dispersion material is excavation larger stress ejecta and explosion leaving with more and at to material, the part volume small-size two the represent than the and attenuation greater this 200 between radii. O'Keefe, by Data when no ejected scaling a the craters. amplitude to of inherent representative fragment on large inherent identical crack stage the begin m/s targets the compaction, much the the local System shift Moreover, in the represents craters the craters the distances transient ejection and ejecta ejection number primary relation 6% a proper- aerody- at has coales- Debris moon, 1977). at shock shock of crater larger larger rates flaw- with such flaw size size and and will nu- left the (6) on at is 1978LPSC....9.2857S 57%-69% from corresponding different Fig. umes volumes (upper © Lunar 13. crater relative value). reflects Calculated size O >- e I- () 0 > w -, ...J z w w of and rim) 1oom/ ejecta to (top). sols been 10'%,_ to The approximation total Planetary for /s this 0.1 ejected will ballistic a ejection Given 111111111111111111111111111111111111111111111111111 ejecta ~RANGE Orbital ejection 40 VOLUME EJECTED _____ 40%-55% 29%-44% 57%-69% 20%-35% 9%-20% 6%-16% land Va'= km • FRACTION Institute an at volume range beyond excavation velocities infrared CRATER i-0 velocities ejection velocity of 200 lOOR transient SOR 10R 6R 2R 3R (scaled (mass) .., two 0.2 m/s • observations _____ 10 40 20 is at velocity, 1 Provided 0,.5 5 -,A-M~E~T~E~R diameter equal crater also .• -- :,,,,' ,,/ different OF ejected cavity to DIAMETER ,,' ,, ,,' ,,' ,, ,, , ,, ,, ,,' ,, excavation ,, to shown. ,,' ,,' ,,' ,, radii ,, , ,, CRATER ,, ,, ,, ,,' ,,' graph or as crater ,, ,,' ,,' ,, by ,,' ,, at ,, , of ,,' ,,' ,,' positions , an , greater from ..,.,... ,, ,,' ,,' greater the ,,' ,, ,,' ,, 0.4 lunar For ,,' , ,, ellipsoid ,, .,, also 11 and ,, ,, ,,' ,, , NASA ;•' crater radius , __ ,,' example, (KM) ,, than craters shows that , velocities. RADIUS (bottom) 0.6 ... center (lower from Astrophysics this 200 __ the graph material m/s. the (one value) approximate 0.8 within Range ,.._.,. crater suggests crater 1.0 or must in craters Data cylinder ejected center) radius have that vol- System of 2879 1978LPSC....9.2857S 2880 by probably from tion Delta suggest action then During crater for will ent flaw imately rim ejecta final deposit increased considerable different the the nution before similar. ejecta excavated at ejecta. may greater coming pacted) of blanketing composed controlled of modify ejecta ( <10 Shock-fragmented In This least Curran the very crater rim, ejecta from © initially ( have size undergo summary, is Curran size a cm), shows Lunar before within deposit may associated target. material flow. simple sheared This that the model the distances and 10 comparable Residence small ejecta small impact distributions related for ejecta formation distribution those times from debris of by et and of the stage regolith result material and the shock-fragmented possibility a et impact comminution the small al. Rather ejection considerable the joints size Because size power-law that pronounced does resulting ejecta 20 al., and Planetary exits upward a 1 a configuration the observed between fraction to (1977). transient of from around with final in seconds, primary times ejecta size the was l km and layer radial locally increases, 977). surface and and not small-size initially the debris it size and of of increased deposit. the inherent flaw diameter fragments seems emplaced suggests along other ejecta Institute crater within The subjected the preclude volcanic suggest craters resultant that 40 description (see distributions For around possibly crater motion, comminution. rim, occurs crater P.H. whereas increase excavated sizes also over incipient moves and measured of weaknesses consistent Schultz, the either basalts, thereby are debris Moreover, it debris systems larger flaw-size SCHULTZ residence ejecta crater • less that before may that travels for ejecta 122 representative ejecta, as within an the crater Provided experimental also to greater the ash. radially the in a most do than and appreciable large ejecta initially target. seconds. impact significant a may change ejection ejecta highly such for target implying impacting the will 1972, expected of and ejecta ejection. same Although may along not volcanic with As wall distribution the reflects in times. crater large 30 small-size by naturally comminution. small-size shock W. have be outward flaws crater may the excavate comprise 1976). process the craters interactive undergoes km result ejecta (Gault the contributing their MENDELL the size recombined Hartmann of craters longer of craters upper NASA residence rays Such to to are be in Models pressures conduits the time. wall preserved the relatively diameter the distribution ejecta be form size occurring diameter in from fraction ejecta (more reduced of of generally et represent ejecta incipient a large Astrophysics a significant a initial of small. accelerating target may residence further al., history the owing comminution Interactions compaction system distribution To the of secondary the times (1978) mass and to (perhaps than and as be material size 1968; is impact fraction spectral first large flaw from enlarging and to point the (Schultz, increased, materials breccia. significantly less to for impacts flaw-size comminution contributes increased for of near two between blocks fraction times order, size carried near-rim Data points Orphal, two a size primary primary-crater fraction than of crater pre-Schooner mechanism craters. 30 and loosely as minutes) that between signature by the distribution impact is System processes: crater within However, fragments described by km 1978). or the are probably 5 distribu- grinding out the some with approx- may departs commi- original growth cm. groups simply 1977). differ- ejecta to of crater crater near- small Near com- time that and and and the the the the are At in- be of of is 1978LPSC....9.2857S secondary Acknowledgments- W. emplaced of chus ing Curran ciation This signatures to Ahrens Gault low-rim Frandsen impact Gault Gault Gault Guest eds.), on 63 earth tigations. p. Technical rock. oid gravitational Baltimore. Shock 2873-2894. Merrill, The The Although be the L. 2. 4. 3. 1. the paper 1057-1087. pp. the displays impact. Quaide. D. D. D. J.E. D. concentrated under D. T. Fragmentation effects Comminution interactions. Increased Blanketing media. © observed Proc. characteristically p. thermal Metamorphism fraction melt. E., moon. E. E., A. and side Lunar J. R., eds.), 639-656. constitutes (1973) Project Information. after and craters, Shoemaker are and D. Quaide Contract NASA Shockey 6th Wedekind The In acceleration. all of similar of Pergamon, (1967) In Heitowit p. O'Keefe consistent and Impact Hypervelocity Stratigraphy the of mechanisms ejecta Lunar 1231-1244. Impact record The gravity thermal fraction Plowshare Pergamon, W. TND-1767. of Planetary small-size the No. and D. around crater Project of E. authors L. and J. ejecta units of and J. Lunar A., E. of Natural Oribital NSR and M. emplacement. and (1977) N.Y. crater In D. of scaling primary-crater Explosion D. Planetary non-blocky primary-crater Seaman features. with and of Impact of Pergamon, where Pre-Schooner II, Pre-Schooner Final Explosion (1977) Oberbeck N.Y. with 09-051-001 (1963) Impact and and gratefully two Institute 39 deposits ejecta small Materials ejecta probably Experimental Moore infrared CONCLUDING rays pp. the Planetary Contract within similar L. and and Equations craters Partition Cratering smooth-surfaced Institute Symp., from and interpretation size H.J. can V. REFERENCES Cratering Explosion with N.Y. acknowledge • with increased observations (B. by ejecta Austin Provided R. Olbers the dune-like contribute pre-impact Institute be (1963) Report, ejecta p. and M. a the ejecta is also (1968) of increasing hypervelocity Postshot of (D. lunar operated small-size 419-456. explained energy French state National M. (D. 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