1979LPSC...10.2899S
of
of
Abstract-Basaltic
impact and
partly
geochemical A basin
lunar
occur
distribution Such represent of units
proposed
extrusions
itative
(0.06-0.09)
Mare
identify
event. impact of
Spectral map
McCord,
this
continuous
global
Mg-rich
local
Maunder.
basaltic
a and
suggests
on
re-exposed
dark
record
craters
basalts
proposal
©
photometric The
ejecta
survey
light
ancient
identification
possible
light
Lunar
stratigraphy,
of
and
of
materials.
1976;
data
Lunar
Department
smooth
KREEP
volcanic
chemistries.
has
Evidence
plains
elevations
resulting Identification
that
that
on
plains
on
of
deposits,
is
geochemical
support
and
basaltic
by
been
the
volcanism
and
consistent
mafic
dark-haloed
Johnson
the typically
pyroclastic
units,
subsequent
Planetary
ejecta
units
and
activity
Consequently,
plains
Planetary
of
masked
characteristic
between
of
units
the
units
dark-haloed
buried
mare
notably
provided
Proc.
Geology,
exhibit
of
they
deposits
clearly
interpretation
with
during
also
dark-haloed
et
covered
interpreted results
by
impact
for
Lunar
volcanics
are
Institute
smaller
Institute,
basalts
data
maria
al.,
Printed
may
ejecta
mantling
south
new
similar
may
exposed
Peter
the
generaily
Planet.
INTRODUCTION
Arizona
of
Paul
at
ancient
that
craters
1977).
by
topographic
generally
in
and
be
large
from
pre-date
impacts.
first
least
is
of
deposits
craters,
has
temporally
the
•
3303
Sc,.
ejecta
that elevations.
impact
also
Mare
re-exposed
light
Provided
as
United
the
1.5
D.
H.
State
craters
deposits
as
some
Co11}.
been
larger
the
2899
dark
the
Where
NASA
consistent
b.y.
recognized
the
debris
plains
This
Humorum
basaltic
dark
Spudis
Schultz from
States
craters
10th
dark
University,
therefore,
presence
of surface
data
confirm
of
overlapped,
impacts
than
used
such
mare
by
Studies
(1979),
process
the
Road
of
lunar
large
as
from
ejecta
halo
(Heiken
mare
demonstrating
Amenca
the
in
on
about
with
an
as
smooth
units either
lavas
p.
and
the
history.
(>
1,
the
responsible NASA
the
Copernicus,
indication
2899-2918.
deposits
by
previously
is
Tempe,
this
is
of
Houston,
basalts
lunar
100
volcanism
can
in
1
distal
ejecta
may
last
thereby
clearly
clearly
km
mafic
their
the
highland
et
(Wilhelms,
implicitly
km)
Astrophysics
orlto (Pieters correlation
Between
major
sample
be
represent
reveals
al.,
eastern
ejecta
Arizona
contain
that
of
impact
illustrated
from
relatively
have
Texas for
creating
important
have
minerals.
Langrenus,
contrasting
associated
1974;
basin-forming
plains
crater-contained
the
data
deposits
3.0
that
hemisphere.
significant
85281
a
77058
only cited
craters
been
or
last
later
and
wide
1970),
and
Data
Head, they
are
by
explicitly
the
major
low
a
3.9
This
of Theophilus,
origins.
indicators
dark-haloed
buried
implies
believed
but
diversity
contrasting
cratering
commonly
System
last
Orientale
with
AE,
fractions
impacts.
albedo
and
1974).
Orbital is
basins.
stages
qual-
mare
then
and
part
The
that
by
an
to to
to
in 1979LPSC...10.2899S sufficient consider impact lution third, derstanding impact 2900 ies McCord, but ference on graphically al., Dark-haloed sonable volcanic the excavated of contribution originally velocity from Oberbeck decreases denhall, Wilshire, ( osition 1976). appear dark However, this typically et <15 In Figure Dark Photometric IDENTIFICATION medium-size al., ejecta and, contribution was 1976; © type the pre-existing unit km) we Lunar provided Dark-haloed craters crater processes. to 1976). images for prior ejecta improbable 1979). following the impact vents of are Andre deposits 1976). 1 1975; discuss build-up lower P.H. with decrease are as primary et mare demonstrated certain illustrates impact and the global craters of concentrated shown al. to and most These that deposits decreasing of (Shoemaker, Because contrasts Planetary Schultz, mafic Schultz early craters by higher of by stratigraphic et basalts (1974) Whitaker topography the that of discussions, dark-haloed primary al., may ejecta of melt occurrence impact spacecraft, rapidly likely ejecta have for in preserved Langrenus stages material significance impact-derived stratigraphic and the 1978) resolution such also Fig. OF provide other deposit have Institute dilution 1976; buried been in also material to crater swarms near craters P. crater material with (1972) laboratory-scale IMPACT-EXCAVATED occur of reveal 1962; as as 1. D. horizons or suggested craters Hawke clearly can to of pits lunar it we well Dionysius Albedo topographically by with an signatures Spudis • time, oblique size, of (Hodges, the is became spacecraft dark-haloed and Provided illustrate of can as Salisbury develop address or indication primary ejecta and mafic in inversion sufficiently as deposits basaltic the resembling dark impact ejecta identified color-ratio and weakly agglutinates whereas the be in are craters contrasts that impact. certain inferred units clearly clear ejecta deposits by (Schultz, Head, ejecta 1973) deposited of first the between ejecta deposits impacts views, the melt et secondary volcanism. of believed bonded by primary craters along process symmetric from hidden old that low al., NASA the buried deposits rays and Figure images impact identified halo 1977). the ancient ponds associated by in of to typically identification portions 1976) 1968). this earth-based (Gault around fractures Copernicus excavated from on MAFIC Astrophysics secondary in crater the Copernicus. ejecta permit is to by ejecta mafic of 2 However, impact of non-mare structures, and top confirmed interpretation represent of permits stratigraphic long-term mare and dark soil, Theophilus Johnson in With et large small Copernicus were of flows layers. of (Schultz with the soil may al., (Carr, Picard MATERIALS haloes higher the cratering see deposits highland ejecta telescopic increased Data (Schultz, impact ejecta of maturity comparison impact interpreted 1968) terrains. melt such deposits (Howard indicate an The rim by et e.g., dark-haloed Pieters impact Second, 1966; (Pieters System al. excavated (Saunders and persist. horizons. color-dif- inversion generally was resulting deposits deposits wherein inferred craters. for craters H craters (1977). dilutes plains, Men- 1969) 1972, stud- reso- (i.e., And low- dep- that rea- and and un- we as et of 1979LPSC...10.2899S
~--.. - 1 .· 'j·!/,....,~,' ,{-, <•'' ,' . .·:./V' ;ii, ' . .,,: ' @ ,..Ji. •:'~·.iflfl;/!'~ ' ',,, _... • t""' ' '' :1$'"' ·;;,.,,., :·":' .·: .~,f~t ''* -~~>~-~- = ,(,_ '¥,;.' = ,;,,;••' e; • _..,,,,,_, '-::~{ _.i.,,:j,:-',:)~\ =Q. -,,.~~" "_,~_;a"'., -;.'-'~'-:,',' ,, ::si "'-~.~«! '""" ' ' [
..... ,.,,,-,, ,.-~ .... ' ~· ;'"
• '' <~· t'rl , •'. '1'· "'.'. 0 '.. -.ti:: J"t· ....< w·· c..: Q. •t,i - .r'' ,•":-':_ ::3 °"(") Q. t ., C" ~;t:,, • °" '-< •• :,:¥;i?~ .:.~ --: ; -L ~-. - :::::, ' ?' ,,(:-,. ::3 z (") > ~•-·•.-~- ~- rn ~~_i:~!-• . ::3...,_ > ,, ._ -~ :::l > ,! :::::, Cll ,.., ~~-- ~- --: 0 ..... 't< _',-~- °""'.'. "C \~ ' ' .;,,~it•',.•,:~· .._Cl '-<=- :'.>i'' (b) (") Cll ~.,,.' '••:,•~~--- ' ... 4-'. :::::, ....t') ::3 Cll c::;· 0 Fig. 1. (a) Comparison of high-illumination view (top) and color ratio map (bottom) (Whitaker, 1972) from earth-based photog- :::l a raphy showing the dark-haloed craters around Copernicus. Arrow locates the dark-haloed crater Copernicus H that has exca- rn vated blue-colored mafic material from below the ejecta deposits of Copernicus. (b) High-resolution view of Copernicus H from '-< Cll ;'" Lunar Orbiter images (LO-V -147-M). Crater form and ejecta facies are characteristic of impact craters in its size class (about t-v s 4 km in diameter). \0 c:,._ 1979LPSC...10.2899S
w -~'~ ."'i ., ' , -.,
@ t"" = "'I ::t: ,v) V'.l =Q. ,. (") "tl ;::s- ' ' .:: § N .....!'0 -- ;:: ..... 5l .....s t, • ~' ti.:: "tl c:;· 8.... Q. i. a' '< ~. g z >rJJ. > > ::t"' .§
"'....n "'t, Fig. 2. (a) Dark rim patch on 12 km-diameter crater south of Theophilus as revealed in earth-based photograph. (b) Lunar ! Orbiter photograph (LO-IV-84-H2) showing topographic low along rim where dark patch occurs. rJJ. Asymmetric ejecta deposits '< may indicate either dark substrate or impact melt. Craters thought to display melt deposits are not included in this "' survey. 3 1979LPSC...10.2899S which erage metric the which pirical different dark-haloed ter (Hasselblad, km. problem (Fig. (high-resolution exclusion ejecta craters in lighting For tions material. trasts haloed phy). due information to craters craters identification identification sible Craters dated mation (1200 The albedo As The low-resolution, their rays) absence to example, This Mare volcanic to 3b). a Exceptions is km by such © deposits exhibit typically selected contrasts techniques composition craters and on on than result this (e.g., angles Lunar that extremely surroundings, of were illuminations mare First, further diameter) restriction small And previously Australe these large as exclusion of about craters most metric, excavate of of of albedoes vent Copernicus, and photographic generally light with absolute sufficient basalts. and craters fourth, the exhibit mare underlying craters Apollo the may exceptions ponds Planetary to Occurrence avoids wide-coverage buried exist near-side (elongate variable attempts bright outweighs crater plains that basin region preceding this panoramic provides ponds include be unrecognized mare (Kuiper were but candidate Some of values albedoes of in to avoided. photography to most misidentified size photometric units. the ray Institute deposited size containing impact the determine discriminate Langrenus, only units in are and sources are classified maria to units pits a of restriction order systems likely h southern the contrasts of highlands of a limitations, few range restrict also et frames), noted. the generally along the large albedoes, of is views dark-haloed craters melt. from al., • and obvious ambiguous. basaltic excluded, of Evidence 0.12, mare Provided include could on first was numerous and the as contrasts as 0.2-0.3. fractures) (e.g., Second, examples 1967), sample are Maunder) in It beneath a even due Mariner include that strong, must possible surfaces and absolute dark-haloed generally class also order exhibit low-resolution several indicate regions believed dark-rayed lunar units. by earth-based to for Tycho) might lighter as since much impact the of unifies be the crystalline/glass The Such is ancient between superposed to moderate, ejecta to clusters well or 10 craters NASA hemisphere poor mare confirmed were in criteria summarized dark with avoid albedoes, mature dark excavated they restricted reveal and survey are to lighter ray this regions as the impact craters craters mare deposits photometric represent Astrophysics halo very deposits. excluded Zond generally do mantle telescopic materials. Lunar local of melt region earth-based and scale were significant soils and not concentrated crater smaller volcanism craters must high by with photographic crater between such is 8 partly deposits ponds photometric reveal weak in of content. patches. Orbiter, photographs. used where exhibit resolutions of a very Although albedoes be avoided. except strong the this ray large Data as large Third, views dark-haloed partly from calibration. identifiable avoids in to and new Dionysius significant photogra- data deposits, contrasts old analysis. 1 System of contrast a identify circular Excep- Impact Apollo and impact photo- on higher a where bright under infor- mafic dark- inun- units (cra- base This cov- con- 2903 pos- em- and the the 20 In 1979LPSC...10.2899S
1-v \0
@ r' = '"tl ""I :::t: § Q. V'J "t:I § ::::.... re N-- ...... ::, ;:: .:i...... '"tl 1;l ..... t,
~<' < ..... ¼•~ •• ' '\..-_. '"':11:l'" re " i : ' ' . ~', "" 0 '> it, • + ' "!:" - ',,....,,. ..£<.i >. ~: ...... - :::: "t:I !:2-: 8 "' s:re Q. C" ,, ' '-< ·"4'-: Ni~/~'f , " t ..... l • '"t { - ,. =-re ,, ,, z ,./11:. >00. > '> > "' q (a) t (b) '§. '-< Fig. 3. (a) Small craters that have excavated very dark materials from below the ejecta deposits of Manilius (Apollo 15 metric "'n... "' frame 2570). (b) The 18 km-diameter crater Dionysius that exhibits dark filamentary rays over adjacent mare plains and highland ael plains. Dark rays are believed to represent deposits of primary ejecta (Apollo 15 metric frame 2562). 00. '-< ;;-"' =
1979LPSC...10.2899S
from from
cluster cluster
craters. craters.
that that
exhibit exhibit complex complex
includes includes
consistent consistent
represent represent
El-Baz, El-Baz,
and and
unit. unit.
type type
haloed haloed
discussed discussed
Other Other
A A
have have
L:~~i-
Kuiper Kuiper
global global
Significantly, Significantly,
the the
lmbrian lmbrian
(ASS-12-2192) (ASS-12-2192)
exhibit exhibit
Fig. Fig.
haloed haloed
Basalts Basalts
© ©
craters craters
of of
the the
Figure Figure
Lunar Lunar
1977; 1977;
numerous numerous
craters craters
stratigraphic stratigraphic
4. 4.
smooth smooth
lightened lightened
-., -.,
excavation excavation
pronounced pronounced
below. below.
with with
Mare Mare
characteristic characteristic
inventory inventory
a a
impact impact
generally generally
(1962). (1962).
wide wide
plains, plains,
and and
Whitford-Stark, Whitford-Stark,
occur occur
long-term long-term
5 5
Australe Australe
Humboldt Humboldt
range range
plains plains
shows shows
craters craters
Planetary Planetary
this this
with with
dark-haloed dark-haloed
Although Although
were were
of of
in in
dark-haloed dark-haloed
reveals reveals
history history
in in
dark-haloed dark-haloed
inferred inferred
region region
a a
emplaced emplaced
suggest suggest
and and
age, age,
albedo albedo
not not
an an
morphology morphology
lightening lightening
dark dark
Institute Institute
and and
area area
on on
around around
mapped mapped
at at
involving involving
the the
the the
that that
that that
mafic mafic
the the
Jenner Jenner
mafic mafic
least least
1979). 1979).
craters. craters.
within within
near near
plains plains
widespread widespread
moon moon partly partly
craters craters
mare mare
• •
craters, craters,
of of
a a
Provided Provided
Evidence Evidence
partly partly
unit unit
unit unit
the the
old old
as as
of of
Figure Figure
(Hartmann (Hartmann
the the
plains-filled plains-filled
near near
results results
the the
units units
materials materials
Although Although
craters craters
impact impact
maria maria
overlain overlain
elongate elongate
predates predates
indicate indicate
surface surface
the the
Humboldt Humboldt
as as
which which
may may
by by
from from
for for
mare-filled mare-filled
occurrence occurrence
a a
4 4
within within
the the
result result
also also
shows shows
craters craters
be be
ancient ancient
ejecta ejecta
by by
and and by by
have have
the the
NASA NASA
in in
crater crater
the the
basin basin
excavation excavation
considerably considerably
the the
exhibit exhibit
lighter, lighter,
deposition deposition
Lunar Lunar
and and
of of
Wood, Wood,
dark dark
Orientale Orientale deposits. deposits.
crater crater
an an
degraded degraded
been been
mare mare
(Fig (Fig
Astrophysics Astrophysics
burial burial
identified identified
Schiller Schiller
Jenner Jenner
(Fig. (Fig.
area area
ejecta ejecta
Jenner. Jenner.
Orbiter Orbiter
less less
5b). 5b).
dark-haloed dark-haloed
volcanism volcanism
mapped mapped
1971; 1971;
darker darker
Numerous Numerous
by by
of of
Australe Australe
6) 6)
near near
of of
basin, basin,
impacts impacts
mafic mafic
Fourteen Fourteen
that that
ejecta ejecta
a a
of of
deposits deposits
Mare Mare
impact impact
by by
Wilhelms Wilhelms
Data Data
buried buried
at at
photographs photographs
dark-haloed dark-haloed
Jenner Jenner
as as
contains contains
depth. depth.
Hartmann Hartmann
basin. basin.
plains plains
as as
units, units,
dark-
System System
deposits deposits
Cayley-
is is
further further
impact impact
ejecta. ejecta.
might might
mafic mafic
dark-
more more
2905 2905
that that
and and
the the a a 1979LPSC...10.2899S
N .;,><; IO . . ,(. •:; .. , i ... ''''t.t:•:f· ' .c · 111' ,#';,,; , 60° 75° 75 ° 60° 60° 75° 75° 60° 22 5"-0 +-----'-----'----+----~---~----+- 1225° I_L_ @ ,754 '"V~ •75+ t""' I = /-- e; •50 ..... 90~-- /,<180° =Q. 225 0 270° 90° I ::si I __r-,-- -:t . [ ... 'f _L_ • 40° _l_lw [ • • a, 2908 brian impact The Mare El-Baz Mare a arranged Mare smooth © cluster plains Australe Undarum, Lunar Fig. Crisium craters and craters (1977). low-lying El-Baz, P.H. plains 7. of and with Light materials dark-haloed on (75°E, Schultz (1 The Planetary dark region 1977). and l0°E, plains non-mare plains-filled haloes. cluster western Apollo 10°N), and north region 30°S). centered Institute Plains P. craters 16 around units. and D. northeast south The Mare metric are Spudis regions • on east Provided concentrated northeast last The frame a Marginis. of Mare of degraded of Mare two most Mare including 3029. Mare by Crisium regions of the agns exhibiting Marginis within pronounced Humorum Mare basin Marginis NASA possible the occurs have identified Marginis Astrophysics areas (45°W, been (100°E, impact clusters in of numerous the (Fig. discussed basin by Mare 50°S), Data 20°N), concentrically Wilhelms occur (Wilhelms 7) System impact Spumans, occurs and on around above. near Im- and in 1979LPSC...10.2899S Orbital available The and of 4 spectrometer craters. the (1978). Imbrian-age values northeast (Andre and altic et to these with Al/Si where rich (1979b) and two Origin a is lated in generally impact crater Tsiolkovsky volcanism haloed pre-existing Dark-haloed ppm. buried Regions Pronounced this al., partly the regional light the southwest impact basalts Spumans inferred volcanism these ponds ratios intensity © Al/Si anomalous Mg/Si of 1978). within of geochemical The crater craters characteristic One et have It Lunar plains, mafic orbital masked buried less of the al., would west predating plains. craters thorium and numerous ( with ratios basalt light radioactive ejecta Smythii <500 Thorium intensity suggested impact data mafic and the Langemak Mg/Si appreciated exhibit 1979a) of mafic layer clearly on ratios of but geochemical the mafic Smythii terra appear plains by Planetary anticorrelation Smythii crater reveal (Hubbard the exhibiting km2) surfaces. deposits, thereby data also orbital composition concentrations Tsiolkovsky. has anomalies crater craters intensity pooled suggesting in units (1.0) ratios dark-haloed mare-like moon. concentrations illustrate materials that (68°E, these within the high, been that Neujmin also significant and Institute including in ground rays according plains-filled approach Mg-rich units This data. in et a the not in units exposed exhibits north diffuse l5°S) ratios old occur al., Mare the significant a from between and Mg/Si of highlands only of process A Discussion smooth • Recent track craters. apparently impact are by 1978). light Provided the lateral effective of Evidence that mare indicating similar basalts corresponding on basalts low-albedo in Necho. Australe mare to were a by the deconvolution KREEP-like intensity and dark these crater pronounced the plains corresponds Mg/Si data basalt improvements plains is these Figure craters crater quantities variations Figure where levels sequence by old reveals farside obvious for of may ejecta role The exposing a regions the reduced units Babcock lower and in and Al/Si basalts events possible ancient region halo. 8 Balmer, ratios NASA occurring with basalts 9 these have of nearby permits that (1 shows around to adjacent deposits in in ejecta anomaly of in to is of l8°E, Mg may The a on mare approximately north Astrophysics composition. excavated well-known characterized by indicated regions mare the mare (0.8) a the corresponding hidden in the also typically by cluster content. centers the mare-filled a the be photometric direct Hubbard 8°S) deposits on anomalies highlands large volcanism dark-haloed Apollo mixing to of is materials but exhibits basalts lunar locally and spatial light might Maria phase Balmer consistent near of by comparison Eratosthenian non-mare-like on from Data suggests occur Andre maria farside. dark-haloed buried plains gamma-ray impact The in and Langemak a contribute as resolution of early buried and northeast Undarum center 8% mare-like decrease System admixed patch masking contrast (Haines beneath basaltic high impact as region but Keith et dark- MgO units Mg- with 2909 bas- era- that iso- al. on by as of of is 1979LPSC...10.2899S 2910 ters haloed (Fig. before develop If that © ancient of Fig. Mg/Si Mg/Si with 10) 1.0 Lunar 3.9 impact which non-basaltic 8. have and corresponding P.H. AE. ratios The signatures and basalts is highland craters excavated region on • are Schultz Planetary the 110° from • • from were near rim decrease surface may Hubbard and plains. • of ..... Langemak Institute the dark extensive, Langemak P. provide Apollo in D. "veneers" and Consequently, Al/Si materials LONGITUDE Spudis • on • Keith orbital Provided containing a ratios the then • clue - .. • - - - . (1978). - - lunar ------• x-ray correlate from (20-100 115° lateral • to by farside mare Pronounced • fluorescence the the • the beneath • NASA with •••• plains distribution mixing (115°E, m observed two thick) (ASS-12-2199). Astrophysics Mg/Si Orientale • experiment. dark-haloed 9°S) is • • necessary that that distribution intensity • - - • - of - • - • - - • • • - ; ; - - • • • -e displays could basalts 120° • ejecta Data craters, Superposed anomalies •• in System mask strong • extruded deposits of order one • • dark- pre- to 1979LPSC...10.2899S @ ,,, \.-<;// :- , , ~"- Q. = '),,.,, "ti- ....('C= ,0', "'1 '-<.... r,, ....= "~:.' !=.... ('C .... • tl'j "ti ,:: "'1 0 <.... ;::: Q. ... :' lllliL ('") ('C , , '. ':' (1:) Q. C" ·,' '-< 'ci'...... ::i ('C ;::: =- ('") ;;;;· z ;::: 'J1> ..... > 21 .::i r,,> ...... (1:) "'1 '~ -t.' + N .._\0 N @ \ ., ':t·1·~· r ' ;,\'~ ... ., .• = ? .:r~~ .,C:l= .. C:l ' ::i:: V'.J Q.= (") :si s:: C:l ... (C.....= N- l::l e; ;:s '< *"4 ..... l::l... 5l =e; t, • s:: l::l... ., c;:;· ...0 Q. (C Q. -a' '<..... g z >rJ1 > > "';:;- "i 0 "0 "'I")... "' (a) (b) t:I C:l I ..... C:l Fig. 10. (a) Zond-8 photograph of dark-haloed crater on the Orientale basin ejecta deposits. (b) Lunar Orbiter view (LO-IV- non-volcanic appearance of crater. As in the crater near Tsiolkovsky (Fig. 9), dark halo craters are believed "' 188-H2) showing to indicate excavation of mare basalts buried by ejecta deposits, in this case from Orientale. 3 1979LPSC...10.2899S existing by by ing, over the vertical ters mixing ( get Before reflect burial, dilution Elevations the thin maria) units 1978). quently, haloed tion might 1966; ever, Early the (isolated ers the elevations elevations in Detailed Fig. Wilhelms, vations at Crisium masking match <100 Although 5 studies the (Scott distinction origin area more elevations lateral .4 in units. in 6. large are Schultz, reveal topographic be © km. m) a the can 3 over the preservation n the and contrast impact of mixing with .9 basalt Lunar only given basin, patches by n the and topographic revealed excluded pooled distant of and of of regions, light AE, Such mixing 1974; The localized concentrated elevations be dark-haloed thousands subsequent the mare regolith this non-basaltic that sufficiently and Pohn, easily between area of 1976). flows. craters the plains since absence subsequent limitations Mare to light Wilhelms units area within and pooled Planetary generally possibility this by and studies vertical formation the from exhibit of occurrences 1972; composition 3.0 masked plains near-rim maps Although dispersed units and However, of within Undarum, light of argument mare may sharp lateral the of basalt craters this AE small near pooled mare kilometers. layers. east of and Institute Milton, light-plains mixing suggest has dark (lmbrian/Cayley of plains highlands) by cratering be plains, of light survey, as old of in mare/highland the 6.2 of deposits El-Baz, and craters volcanic flows. surfaces been vertical considerably large re-exposure ejecta an commonly ejecta ejecta craters the mare Mare Moreover, is of and at moon plains of • 1968; km that important vertical invalid and Provided the restricted Evidence the declining materials impact whereas Since history. lmbrian/Cayley Mare can and elevations deposits above Serenitatis surfaces 1977). deposits. deposits (narrow ancient lunar processes mixing in Howard derived (as this units buried reveal light the occur mixing the for in by as basins Plains) is Spumans). and contrast for more lmbrian/Cayley lunar landing the to near-surface revealed Mare Ancient appears eastern the role last localized decreased. basaltic of that comparing plains or in unit, from of ancient a This and buried at intramare in NASA exhibit reference (Eggleton units few is discontinuous the and major subsequent surface widespread of lower as clusters, Australe are largely Masursky, sites its the was observation units. kilometers; plains lateral mapped to hemisphere same basalts craters wide units mare Astrophysics currently mafic However, unrecognizable. pools, thickness, a phases Apollo dominate elevations (Rhodes, used Deeply second pooled units process contacts and Figure sphere a volcanism variations inferred region elevations not and light mixing units function resulted by extruded craters the than to 1968; Schaber, are of missions, dark all other predominates, consequently, various is concentration argue plains Data effective with mare buried pooled as basalt is 11 emplaced its 1977; that (around impact believed included may implied (Whitaker, from relative Olson illustrated suggested compares halo) owing in depth of in irregular System also the as Conse- against closely exhibit basalts lateral Horz, reflect eleva- flood- 1972). scale. work- mafic dark- how- mare 29 cra- thin that ele- and tar- ex- the by to as to of to in I 3 1979LPSC...10.2899S 2914 both hibit exhibit graphic units. plains of Thus elevations © a light Fig. 62, able (e.g., according nimetered of Crisium according to tained that Lunar represent secondary the the volcanism. Fig. data 63), non-uniform 11. Lunar P.H. plains Mare total uniform mare - 0 <[ > z and Distribution Mare (LAC 11 in cannot to areas to 4.0 80 5.0r 6.0 3 9.o---~~----,;,__------mapped Topographic Crisium) Schultz Planetary shows units .o----l0--2-0--3-0--4-0--50 the location mapped and volcanic concentration Undarum 61), corresponding • elevations elevations Southern and •···· ·~...... generally area ELEVATION mare • and of and that but in units /.-<~---- light ...... Institute elevations ·· of south-central Orthophotomap the only ... (LAC units P. the units . contained POOLED / of in PERCENT plains . . D. Southern ·- Highlands. characteristic plains appropriate closed published to IMBRIAN be 62), Spudis or near relatively • - exhibit of units Provided used DISTRIBUTION ~- / pooled in that Palus maria _:_ highlands :-:-. the SURFACES 7.8 Highlands .. mare : exhibit geologic _ OF series unit. PLAINS MARIA to highlands - uniform they - - similar (e.g., / km Somni plains :- TOTAL by exclude surfaces Mare in - - - of - (SC) similar the that mare-filled represent the maps. - (LAC units. the (LAC elevations (SC) NASA elevations. - is regions and regions AREA directly :::.• not open elevations, OF Elevation Imbrian the 77, eastern 43), within a Astrophysics useful craters). do 78). of ( maria. possibility debris-covered the ±200 not Mare reflect hemisphere Plains Plains 1 data the diagnostic _j_ Consequently, highlands Undarum Mare Mare near Crisium near Spumans/ include thereby m) Both Spumans In are highlands are are are the Data a from crater-con- open referenced that suggesting given separated classified indicator south (E). distribution System (LAC maria avail- the volcanic Pla- region, of do topo- light not 1979LPSC...10.2899S Lunar than the basalts evidence, earlier canism impact volcanic believed KREEP In al., al., time typical tion, thoroughly thereafter, clasts highland occurred identified gests intermediate Mauro time, tween mare originally Concluding expect eries cias in We matrix saltic relation and previously Imbrium The Ryder early the timing propose 1977), strengthens 1976) is about of that suggests numerous textured volcanism. possibly sample strongly © complemented relationship period 4.1 breccias returned from minor highland melts breccias heavy commenced with Lunar history volcanism was and samples present product on impact. ancient from emplaced about that and believed. and prior lunar destroyed 3.9 remarks the a that Taylor between dark evidence and immediately and bombardment phase that lithic earlier planetary AE. is suggest duration orbit 4.25 display moon from and 4.4 single interpretation to mineral ( volcanic only A volcanics suggests dark-haloed derived In ~3.9 Planetary based polymict halo between extrusions the (1976) clasts This small AE as around that addition, Identification AE (Spudis, of by the than by KREEP prior for as pryoxene volcanic the start craters AE) mare postulated (Schonfeld impact of on mare size clasts. the moon (Schaeffer contrary has a ancient from percentage mare in have activity Institute 4.2 following on existence mare mixing breccias. to types its of an (i.e., this possess identification body. basalt led impact the of 1978; AE Ryder ~4.2 volcanism of and as mare that phase Apollo reviewed volcanism processes a Because units, KREEP volcanism time many mare and the moon unit indicative of pre-Imbrian to of to • (Ryder has component mare The affinities, and AE. have Provided Hawke Evidence and early the volcanism. have ancient of orbital Thus, mare suggestions et craters of plagioclase chemistry that but (Head, volcanism 17 been investigators may Meyer, pre-Imbrian overlap al. The the Apollo basalt. a been Hussain, 40 boulder associated and (Taylor, lunar was active and commenced, of subsequently variety Ar- has basalt (1977) became any and of display by lithic as x-ray for mare volcanic available indicate compositions mare age) Taylor, radiometrically 39 1976), the ancient in a complex volcanism 1972) The Ar in ancient KREEP program, Head, volcanic (Walker for well-preserved ( impact clasts NASA of clasts chemistry have ~4.0 basalt and volcanic 1973), 1975). were ages a basalts deeply with sample mare integration to on simplicity wide with and excavated KREEP evidence 1976). volcanic gamma-ray based mare conclude AE) Astrophysics 1978) the discussed buried in in presumed for as clasts was derived major et rocks to mare An certain basalt is diversity the that probably some the moon regimes ingrained. evidence one that these al., volcanism have more and mainly and postulated dated earlier basalt in highland possibility by are Apollo from basin (e.g., deposits. units of dating would mafic have flows. morphology 1972) that Apollo in texture; rocks notions ended postdates KREEPy rocks complex impact anomaly these Data to distinct in are pre-Imbrian further on overlapped these for formation. (Dowty Warner have may chemistry chemistry mare period All materials from and System 16 logically younger In isotopic such. ancient discov- fall to shortly 14 ejecta about of these lunar light- mare brec- addi- from been have than be 2915 sug- vol- cor- was Fra the be- the ba- an as of as et et a 1979LPSC...10.2899S 2916 bedrock. deposits Andre Andre should from low suggests craters ginis, trolled basaltic relatively basin craters vating basalts distribution may Acknowledgments-We S. much Association istration. data. B. Mare 4. 3. 2. A 1. R. Merrill © maria. global facies appreciated. grenus, Topographic Analogous partly iting sistent exhibit Orbital Taylor, Dark-haloed suggesting the C. C. suggest Lunar In north Crisium dark basaltic be analogous near and G., This surfaces G., press from Apollo that This of P.H. under dark-haloed and soon viewed Wolfe survey from E. account Wolfe However, the mare and with paper of materials analogous Langemak. geochemical Theophilus, from Proc. J. that Whitaker, large the proposal dark-haloed The Contract inundation J. Schultz Balmer, Planetary after that R. orbital re-exposure R. pre-dating large constitutes available orbital Papike, basalts to impact Lunar early farside proposed as data of Lunar W., gratefully W., craters for the emplacement the the the soil dark-haloed below large Adler impact D. Copernican and and No. x-ray elevations. reveal Planet. x-ray the is and eds.), Institute and buried These craters formation overlapped E. craters Copernicus) units data supported the Alder P. NSR spectral analogous and the Planetary observed I., recognize fluorescence Wilhelms, expanses buried south D. p. Tsiolkovsky experiment Lunar of craters Sci. and and indicate that Imbrium that 09-501-001 volcanism occurrences 1-12, mafic I. basins. Spudis REFERENCES • basaltic occur Clark Conf. (1978) Lanier impact Provided and and data. of pooled of Institute basalts may the Pergamon, and by during wide to in units sequence of data. 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