JOURNAL OF GEOPHYSICAL
RESEARCH, VOL. 89, NO. B5, PAGES 3381-3399, MAY 10, 1984
Venus' The Nature of the Surface from Venera Panoramas
JAMESB. GARVIN, JAMESW. HEAD, MARIA T. ZUBER,AND PAUL HELFENSTEIN
Departmentof GeologicalSciences,
Brown University
Images of the surfaceof Venus obtained by the Soviet Venera 9, 10, 13, and 14 landers have been
analyzedto providea basisfor understandingthe nature of geologicprocesses
operatingthere.The four
spacecraftlanded in the Beta-Phoeberegion at median elevationsin the upland rolling plains province.
The landing points are each separatedby distancesof more than a thousandkilometers.The Venera
panoramaswere digitized and transformedinto various perspectivesin order to facilitate analysisand
comparisonwith other planetarysurfaces.Bedrockis exposedat the Venera 10, 13, and 14 sitesand is
characterizedby semicontinuous,flat polygonal to subroundedpatchesup to severalmeters in width.
The bedrocksurfaceis oftendominatedby subhorizontal
to horizontallayeredplateswith thicknesses
of
several
centimeters
andabundant
linearandpolygonal
verticai
fractui'es.
Angular
to subangular
layered
to platyblocksin the5- to 70-cmrangedominatetheVenera9 siteandoccurmuchlessfrequently
at the
other sites.Blocksappear to sharemany characteristics
with the exposedbedrockand are interpretedto
belargelyderivedfromit. Soils(particles< 1 cm)areabundantat theVenera9, 10,and 13sitesbut are
uncommon
at Venera14.Featuresindicativeof a strongeolianinfluence
(moats,dunes,windtails)are
not observed.A striking aspectof the Venera landing sitesis their extreme similarity despiteseparation
distancesof thousandsof kilometers. Several hypothesesare consideredfor the origin of the bedrock
surfaces,
andweinvestigate
in detailthehypothesis
thatbedrock
originated
fromsurface
lavaflows.In
this interpretation,the broadly platy nature of the surfaceis analogousto the rolling and undulating
natureof terrestrialpahoehoeflowscausedby the formationand deformationof a semisolidcrust.The
layeringis interpretedto be formed by a combinationof upper thermal boundary layer formation and
horizontal sheetsformed by cooling and sheafingduring flow emplacement.Vertical fracturesare attributedlargelyto joint patternsformedduringcooling.Thisinterpretation
madeon the basisof surface
morphologyis consistentwith Venera 13 and 14 geochemicalresultswhich reported high potassium
basaltand tholeiiticbasaltcompositions,respectively.If this interpretationis correct,large regionsof the
Beta-Phoebearea are likely to be characterizedby lava flows.The relative freshness
of featuresobserved
by Venera 14 suggests
that somebedrocksurfacesare geologicallyyoungor that erosionratesare low.
1.
soil.Comparisons
are thenmadewith the surfaces
of the
INTRODUCTION
Imagesobtainedby landedspacecraftand astronautson the
moon [-SurveyorInvestigationTeam, 1969; Vinegrader, 1971;
USSR Academyof Sciences,1966, 1969; Swannet al., 1972;
Muehlbergeret al., 1972], Mars [Mutch et al., 1976a,b; Garyin
et al., 1981a, hi, and Venus [Florensky et al., 1977a, b, 1982a,
b] have provided fundamentalinformation about planetary
surfaces at scales from milllimeters
to decameters. This infor-
mation providesa meansof (1) documentingthe types of geo-
moon• earth, and Mars to provide a basisfor the interpretation of the surface of Venus.
2.
IMAGING SYSTEMSAND TRANSFORMATION METHODS
Thecameras
aboard
theVenera
spacecraft
weredigital
facsimile scanningtelephotometers
[Florenskyet al., 1977b;
Keldysli,1979;Moro•, 1983;Bokshteyn
et al., 1983].The cameraswere locatedabout 90 cm above the baseof the spacecraft
logic materialson the surface,(2) understandingthe geologic and werepointed50ø downwardfrom the horizontalplaneof
The imagingsystemscansin verticalsweepsof
processes
operatingto form and modify planetary surfaces,(3) the spacecraft.
clarifying the nature of geologicfeaturesand processesinter- 40ø and views90ø to the left and right of the subcamerapoint
preted from orbital spacecraftimagesobtained at lower resolution, and (4) establishinga physicalbasisfor the understanding of the behaviorof incidentelectromagnetic
radiation (e.g.,
radar) utilized in remote sensingof planetary surfaces.The
purposeof this paper is to analyze the information collected
on the surfacein front of the spacecraft.
The camerarotates
about a fixedaxisproducingan inclinedcylindricalprojection.
This particularcameraorientationwasusedin order to allow
boththe near-fieldand the far horizonto be imagedusinga
single,fixedviewinggeometry.
This viewinggeo.rnet•y
results
by theSovietVenera9, 10,13,and14landerspacecraft
imag- in the apparentlyinclined horizon visible at the far left and
ing systemsin order to allow a systematiccomparisonwith right of the unrectifiedpanoramas(Figures 1-3). Objectsin
other planetary surfacesand to provide an improved under- the near field directly in front of the lander impact ring are
whileobjectsnearestthe horizonare
standingof the surfaceof Venus.Plate 1 displaysthe locations relativelyundistorted,
of the Venerasiteson a map of the topographyof the BetaPhoeberegion on Venus.Table 1 summarizesdetails of the
stretched
bya factorof2-3 in thehorizontal
direction.
Veneras9 andi0 wereeachequipped
withcameras
on onesideof
Venera lander missions.In order to facilitate morphologicand
morphometricanalysisof surfacefeatures,the Venera images
were transformedinto various perspectives,including those
utilized in the analysisof the martian surfaceby the Viking
landers[Garvin et al., 1983a]. The array of imagesis described
in terms of three basiccharacteristics:bedrock,fragments,and
with two similar imaging•systems,
located 180ø apart. For
Veneras13 and 14 the 180ø azimuthalCOverage
for each
camerasystemallowed small regionsof overlap in the lower
cornersof the panoramasso that, whenrectified,a continuous
Copyright 1984 by the AmericanGeophysicalUnion.
Paper number 4B0162.
0148-0227/84/004B-0162505.00
the spacecraft,
whileVeneras13 and 14 wereeachequipped
360
øviewofa narrow
portion
ofthesurface
ofVenus
can•
produced.
Veneras9 and 10 obtainedblackandwhiteimages
only, while Veneras13 and 14 obtainedblack and white and
color images•Florenskyet al., 1982a,hi. The dimensionsof
variousspacecraftpartsare listedfor scalein Table 2.
3381
3382
GARVINETAL.' VENUSSURFACE
FROMVENERA
PANORAMAS
TABLE 1. Summaryof Venera9, 10, 13,and 14 LanderMissionResults
Characteristic
Location
Venera 9
Venera 10
Venera 13
Venera 14
31.7
ø,290.8
ø
16.0
ø,291.0
ø
-7.6ø,303.5
ø
- 13.2ø,
310.1ø
Oct.22,1975
50
Oct.25, 1975
44.5
March1, 1982
100
March5, 1982
59.5
2.1+_0.4
1.5_ 0.6
1.4_ 0.3
1.0_ 0.3
4.0ø_+1.3ø
3.1ø+_0.8ø
3.0ø+_0.3ø
2.9ø- 0.7ø
0.10+_0.03
1.9
0.10+_0.03
1.9
0.15_+0.08
2.6
0.14_ 0.04
2.4
3.8
0.03-0.12
3.8
0.02-0•04
5.2
0.03-0.085
4.8
0.04-0.11
,-,90
0.4-0.7
33ø
1
728
91
0.8-1.3
27ø
1
737
89.5
0.3-0.6
'" 35ø
11
738
93.5
0.3-0.6
'" 35ø
6
743
(latitude,longitude)*
Landing
date
Surface
operation
time,•
min
Meanelevation,$
(kin > 6051)
(mean ñ s.d.)
Meanroughness,$
deg rms
Meanreflectivity$
Modeldensity,
g/cm3
Dielectric constant
Surfacealbedo
Surface
pressure,
atm
Average
windspeed,
ms-x
Solarzenithangle
Numberof fullpanoramasõ
Surface
temperature,
K
*Error on specifiedcoordinates
is 1ø to 2ø.
•'Lengthof timeimagesweretransmitted
fromsurface.
:]:From
Pioneer
Venusmeasurements
forregions+_100kmfromlandingcoordinates.
õComplete
(whole)panoramas
(~ 180øin azimuth).
The resolutionof the imagingsystemcanbe definedas the
anglesubtended
by a singlepixelon thenear-field
surface.
For
Veneras9 and 10 the resolutionwas 0.35ø (10 mm per line
panoramas
(Figures10-13).The combination
of perspectives
provides
us with a varietyof viewsof the Venusian
surface
fromwhichto makesystematic
geologic
observations
andper-
to be madeof the sizes,shapes,and spatial
pair),whileon Veneras13 and 14 it was ,•0.18ø(4-5 mm per mitsmeasurements
linepairin thenearfield).Thiscanbecompared
to theViking orientationsof critical features.Details of the panorama translandersurveymoderesolution
of 0.12ø(,• 3 mm perlinepair) formationalgorithmsare summarizedby Garyin et al.
arebasedentirelyon straightforward
andthe high-resolution
modeof 0.04ø (,• 1 mm perlinepair) [1983a].Thealgorithms
rotation
matrix
techniques
[Devich and Weinhaus,1980,
[Mutch et al., 1972;Hucket al., 1975].
images
of thesurface
of VenusfromVenIn order to understandbetter the spatialrelationships
and !982].Photographic
morphology
of theobjects
in theVenerapanoramas,
different eras9, 10, 13,and 14wereprovidedby V. BarsukovandA. T.
perspectives
of thestandard
Venerascene(Figures1-3) were Basilevskyat the VernadskyInstitute in Moscow,and
digitizedversions
of the photographs
generated
andinterpreted.
Previous
workwithrotations
ofthe computer-compatible
by D. Chesley
of theUniversity
of MassachusVenerapanoramas[e.g., Keldysh,1979; Florenskyet al., wereproduced
1977a,c; Bokshteyn
et al., 1983] applieda "rubberstretch" ettsusingan Optronicsdigitalscanner.Eight-bit(256 gray
of each
algorithm
in orderto produce
a flat horizonor a viewfrom levels)digitizationwas used,and the brightness
above.The "rubberstretch"techniqueeffectivelystretches
the Veneraimagepixel was sampledat leastonce.All image
weredone assuminga planar Venusiansurpixelsto generate
somedesiredgeometry
(e.g.,flat horizon) transformations
face.
A
slightly
inclined
horizoncan be seenin the Viking
and doesnot involveremappingthemmathematically
into a
due to the tilt of the spacecraft
on the
specific
projection.
Our approach
is to usea varietyof known landerperspective
tilt has not been
perspectives
whichspecify
thedetailed
geometry
of theimage Venusiansurface.The degreeof spacecraft
determined.
No imageresolution
degradation
has
and minimize distortion in areas of interest. Using this accurately
McGill et al. [1983]
method,accuratequantitativemeasurements
of parameters beenappliedto any of the panoramas.
Vikinglanderimagesto Venera9 and 10resosuchasfragmentsizescanbemade.WhiletheVeneracamera- havedegraded
themto a standard
Venera
viewinggeometry
provides
minimumdistortionin the field lution(,• 1 cm)whiletransforming
For our purposes
thehighest
possible
resolution
closestto the subcamera
point,it resultsin significant
distor- perspective.
tion in the far field. The Viking lander surveymode per-
spective
provides
a viewof the surface
of Venuswith low
was desired.
3.
OBSERVATIONS
distortionin the far fieldand generates
a flat horizonl'Mutch
Utilizingthe originaland transformed
Veneraimages(Figet al., 1972;Huck et al., 1975].We have producedViking
hasbeencompiledon the
landersurveymodeperspectives
of all the Venerapanoramas ures1-13), a seriesof observations
surface characteristics of Venus at the four sites. Surface obser[Garvinet al., 1983a](Figures4-9).
In addition,an orthographic
projectionknownas the polar vationswere subdividedinto three categoriesrelatedto bed-
gnomonic
[DeetzandAdams,1945]hasbeenusedfor the rock,fragments,and fines/soils.
near-fieldsectionsimmediatelyadjacentto the lander ring
Bedrock is defined as continuous, coherent material un-
(Figures
10-13).Thisprojection
furnishes
a viewfromdirectly derlyingsoilsand blocks.Eachpanoramawasexaminedto
abovethe surfaceand providescorrectspatialorientationof determinethe shapeand extentof the areascoveredby bedof bedrockoutcrops
in thenearfieldand
geologic
features
of interest(i.e.,especially
in thelandernear rock,thetopography
field).Thisprojection
hasbeenutilizedwith certainViking on the horizon, the bedrock surfacetexture, structure,and
landerimages[LevinthaiandJones,1980],and we havepro- relativealbedo,and the natureof any layeringevidentin the
aredefinedasdiscrete
blocksor particles
ducedpolargnomonic
versions
of thenearfieldsof theVenera bedrock.Fragments
GARVIN ET AL..' VENUS SURFACE FROM VENERA PANORAMAS
BEHEPR-
13;
OISPAõOTKA
3383
cccP'
UiKC
Fig. 1. Venera 13 landingsitepanorama,sideA (penetrometerside),in originalperspective
prior to transformation.See
Table 2 for details of spacecraftscale.
with diametersgreater than 1 cm. The areal distribution of
fragmentsand their shapes,sizes,surfacetextures,fracture
patterns,structure,and relative albedo were noted.Fragmental material with grain sizesless than 1 cm is classifiedas
fines/soil.The areal distribution,relativealbedo,and presence
or absenceon the spacecraftof this material was studied.Finally, the relationship between bedrock, fragments, and
fines/soilwas examined.The basic observationsare summarized in Table 3. Previous analysesof the Venera sitescan be
found in the work by Florenskyet al. [ 1977a,b, c, d, 1982a,b,
1983a, b, c-I.
Venera
9
There is no unambiguousbedrockunit visiblein the Venera
9 panorama(Figures 3 and 4), althoughthere are a few farfield features and some apparently highly buried fragments
suggestive
of a bedrockcomponent.Fragmentsdominatethe
Venera9 scene,from small particlesat the limits of resolution
to 0.7-m bouldersin the near field and perhapslarger ones in
the far field. More than 50% of the region is littered with
angular to subangularblocks,many of which are platy or
tabular. A significantnumber of theseblocksare polygonalin
outline, and many display planar fractures. Some of the
intermediate-sizefragments(<30 cm) appear to be layered,
while othershave an apparentlyfluted surface.Dark spotsin
severalof the more compactblocksappearto representcircular to subcircular cavities, possibly containing soil. Various
degreesof burial are suggested
by the fragmentorientations.A
possiblefillet can be observedin one of the highly inclined
fragmentsin the near field; sucha featurecouldbe due to fine
materialsdisplacedby the turbulentgasflow from the free-fall
descentof the spacecraft.A few of the lower-albedoblocks
appearto be highlyinclinedrelativeto the planeof the surface
and could be buried to a significantextent. Other fragments
are clearlyperchedon the soil or on other rocks.A somewhat
BEHEP-.-Ft.
!4
imbricate relationshipis suggestedby the spatial distribution
of many of the fragments.The most fundamentalobservations
with regard to the fragmentpopulationat Venera 9 are that
(1) many fragmentsare angularto subangularand havepolygonal outlines and planar fractures,(2) there is a variety of
surface textures representedon the blocks: ridges, ledges,
layers, and pits can be observed,(3) the size distribution is
bimodal [Garvin et al., 1981b; Keldysh, 1979; Florenskyet al.,
1983b] with one group of blocks 1-10 cm in sizeand another
30-70 cm (there is no strong evidencefor a continuousspectrum of fragment sizesat the site), and (4) the spatial distribution is continuous(there are no obviouszones where fragmentsare much less(or more) abundant than the norm).
Below the limits of resolution,the fines/soilat the Venera 9
site may have diversecharacteristics.This is suggestedby the
variable albedo of the soil distributed betweenthe larger fragments.The lighting at the surfaceof Venus is diffuse,much
like that of an overcastday on earth [Keldysh, 1979]. Soviet
photometricmeasurements
at this site [Moshkin et al., 1979]
identified a possibledust spurt during landing which would
suggestthe presenceof materialslessthan 100/•m in diameter
[Garvin, 1981].
Both a near and far horizon appear to be visible on the
left-hand side of the panorama. The horizon at right doesnot
exhibitthis appearance.Although the resolutionof featuresin
the far field is poor, blocksobservedout to the near horizon
are comparablein size to the largestin the near field. These
larger blocks appear to be inclinedmuch like some of the
lower-albedo
near-field
blocks.
In summary,the large abundanceof fragments(from just
above the limits of resolution to blocks tens of centimeters in
dimension)dominatesthe Venera 9 site. The variable degree
of burial of fragmentsthroughoutthe Venera9 scene,coupled
with their generally polygonal and tabular appearanceare
important observationsfor the local area. Of all the Venera
..H ...
Fig. 2. Venera 14 landingsitepanorama,sideA, prior to transformation.
3384
GARVIN ET AL.' VENUS SURFACE FROM VENERA PANORAMAS
Fig. 3. Venera 9 (top) and 10 (bottom) landingsitepanoramasprior to transformation.
sites, Venera 9 is the only one with no obvious bedrock exposures.
l/enera
10
At the Venera 10 locality there is a significantbedrock component, covering 40-60% of the visible area (Figures 3 and 5).
The exposuresare semicontinuouswith both sharp and sinuous edges.Most of the bedrock is generally flat-surfacedand
often polygonal in outline with some subroundedsurfacefeatures. The largest bedrock exposuresare a few meters across.
The surfacesare typically rough at the centimeter scale with
linear and irregular depressionsoften filled with dark fine materials. Ledgelike featuresand promontorieswith up to 10 cm
of relief are observed on some of the exposures.Bedrock topography in the far field may be up to a meter in relief.
The relative albedo of the bedrock exposuresis generally
higher than the fine mantling materials and the patches of
soils and small fragmentswhich separatethe exposures.Some
of the bedrock boundaries are very gradational with the soil
patches.Such boundariesare oftenjagged and suggestan embayment or onlap relationship of soil zones onto bedrock.
Small soil zones occur on bedrock exposuresin what appear
to be depressionsor undulations in the bedrock surface.The
distribution of soil patchesand soil accumulationson bedrock
surfacesis uneven and is related to the roughnessof the bedrock. On the basisof theseobservationsthe soil depositsare
inferred to be thin (perhaps tens of centimeters)and the bedrock is thought to be laterally continuous below the soil.
Many of the low-albedo soil depositsare irregular in outline,
while others display some orientation, perhaps due to a pattern of depressionon the bedrock surface.The higher-relief
bedrock exposureshave a lower concentrationof low-albedo
soil deposits.The bedrock exposureat the middle right of the
panorama (see Figures 3 and 5) has a pronounced ledge or
curved scarp ("cuesta")on which a relatively small number of
dark soil depositscan be observed.
Fractures and dark lineaments are a prominent feature of
the Venera 10 bedrock. Fractures in the bedrock plates often
define boundariesbetweenadjacent plates. Most fracturesare
linear and often either parallel or perpendicularto each other.
Most linear featuresare lower in brightnessthan the bedrock
they traversedue to the presenceof dark, fine soil. Outcrops
visible in the right-hand far field (Figure 5) display linear
boundariesand edge relief of severaltens of centimeters.The
pervasiveness
of thesefracturesand linear boundariesstrongly
suggeststhat blocks derived from the bedrock would very
likely be angularto subangularand platy in form.
A fundamental
characteristic of the Venera 9 site is a lack of
visible bedrock and the predominanceof fragments.In contrast, the Venera 10 site displaysextensivebedrockexposures
but a paucity of fragments relative to Venera 9. A few loose
fragmentscan be recognizedin the region nearestthe lander
ring as well as a few examplesapparentlyembeddedin the soil
materialsbetweenbedrock outcrops.
The fine materials at Venera 10 are concentratedin large
depositsbetween the bedrock exposuresas well as in small
depositsin surfacedepressionson the bedrocksurfaces.They
are lower in albedo than the bedrock, have particle sizes
below the identificationresolutionof the camera(1 cm), and
contain a coarse fraction made up of centimeter-sizedfragmentsof a higheralbedo.The soil patchesof the intermediate
field of the Venera 10 panorama generallyresemblethe soils
at the Venera 13 site (Figures 6 and 7) in texture and areal
TABLE 2. SpacecraftDimensions
SpacecraftPart
Dimension
1.2 m
Outer diameter of lander ring
Pentagon on lander ring
5 cm high
Color
8 x 8 cm squares
5.3 cm wide
test chart
(inclined 30ø from horizontal plane
of spacecraft)
Yield strength"arm" (penetrometer)
Small
circular
structure
at end
Large circular structure
Lander ring "teeth"
60 cm long
6.5 cm diameter
9.5 cm diameter
7 cm long
4.3 cm wide at base
Camera heat shield (lens covering)
20 cm diameter
GARVIN ET AL.' VENUS SURFACE FROM VENERA PANORAMAS
3385
Fig. 4. Venera 9 panoramain Viking lander surveymode perspective.This is a cylindricalMercator projectionsuch
that the horizon should appear flat if the spacecraftis not tilted. In such a projection, distortion is minimized at the
horizon and increasesas one approachesthe spacecraft(e.g.,note the appearanceof the circularbaseof the spacecraft).See
text for further
details.
distribution. Some of the fines at the Venera 10.site may have
beenperturbed by the spacecraftlanding and carried aloft in a
dust cloud that later settled in the near field [Garvin, 1981].
This suggeststhat the soil materials are loose enough to be
mobilized by a gas flow resultingfrom wake turbulencedue to
the spacecraftlanding (spacecraftterminal velocity of 8-10
m/s).
Summarizing observationsof the Venera 10 locality, the
most characteristicfeatures are that (1) significant bedrock
exposurescover up to 60% of the visible surfacearea, (2) there
is a paucity of discrete fragments (those fragments that are
observedare at least partially embeddedin the interbedrock
soil patches),(3) fractures and linear features are visible on
bedrock surfacesand often display orthogonal or parallel relationshipswith other fractures,and (4) fine materials occur in
bedrocksurfacedepressionforming regular and irregular dark
spotsand patches.
Venera
13
A factor of 2 improvement in resolution for Veneras 13 and
14 over that of Veneras9 and 10 (4-5 mm versus10 mm per
line pair) allows small-scalefeatures to be better characterized.
At this higherresolutionit is possibleto characterizein greater detail the coarsefraction (5-10 mm) of the particles that
make up the fine/soil component.In addition, small-scalefeatures such as pits, undulations, and possible clasts can be
recognized.Figures 6, 7, 10, and 11 show the Venera 13 scene
in various perspectives.
As at the Venera 10 site,there is a significantbedrockcomponent at Venera 13, with up to 50% of the visible surface
Fig. 5. Venera 10 panorama in Viking lander surveymode perspective.
3386
GARVIN ET AL.' VENUS SURFACE FROM VENERA PANORAMAS
Fig. 6. Venera 13 (sideA) panorama in Viking lander surveymode perspective.
consistingof semicontinuous,subhorizontal exposures,many
of which are polygonal in outline. Layering of bedrock exposuresis suggestedby the characteristicsof fragments and
their relationship to bedrock. The bedrock displays a variety
of surfacetextures,someof which suggesta regular pattern of
depressions,ridges, or undulations on their surfaces.Most of
the bedrock plates are subhorizontal,but in the far field there
are exampleswhich appear to be more highly tilted relative to
the plane of the surface.The boundaries of the bedrock exposures are of two basic types similar to those observed at
Venera 10: (1) sharp and often polygonal in outline, and (2)
diffuse and gradational with soil zones separatingexposures.
Thesediffuseboundariessuggesta burial effectin which bedrock is mantled by a layer of fine materials severalcentimeters
thick. The sharp boundariesoften display a few centimetersof
reliefi
The bedrock exposuresor plates at the site are up to a
meter in extent and have textured
on the bedrock surfacesare often filled with dark, fine material
onthebedrock
surfaces
butappear
to be•.•.•..?e
irregular
in
.• •.:::...,...
-,,.-[.:..:.:::..?:;
,
•.. '•.,...
.............
in form
producing an apparently mottled surface. Several bedrock
plates have surfaceswith subparallel depressionsfilled with
depositsof dark soil. Linear fracturesalso occur in abundance
•i•':-";--::*'
r
surfaces reminiscent
of those at Venera 10 (Figures 5 and 6). In addition, 5-10 cm
of surface topography can be observed on the exposures,
manifestingitself in the form of cuspatescarpsand a variety of
surfacedepressions.The cuspate scarpsresemblethe cuestalike scarpidentifiedat the Venera 10 locality.The depressions
.
*---.:.,.,;,,•4};.:;"
,. ::......:;:,:... .#
'.......
":*:'
"'*'"'Z" .-'...'•
':'*
.,.,:,;X(*-:½'•**-.;;
...........
---'....:::•....-"'
........
..-,:.;,,-,::::•.
.
-.
"•':
"*:•---'*
'-"',
::
......
*.....
:::'"*"
::•......
,;i:'*"½S:'
*".½,..--'
,'...--""'
........
:7'*"'.....
"';.-.
"'.,.-'
-:.?'•:•
""'""
'*"*-'"'
:'-'*-"
,.;":'•'*•
.'"
'•,
;'.'-:".::.--I,,;. .-<';{*•'
-":'•
....
...
...........
,*.*:"*
7•'"':**
..........
'"' .... "; .... *"*......
:;.,. ....
. :k.: , ..,.
'....
"*
....
.,::,:. .... :..... :..-:.
:'" :'*"*:'
'" : ' '
,-E,.,..,• .
- :...........•
-::,.•..,;,
';*k*::"
'.: '" :':'?",
.....'-: -:,"
';:•:.? •I •f'•7T '• *'""'•*
"-'":
"*.t:
:..,-'
;;•':;
•:.)".::':"
:.:;:
'-....':'•'
':-?,.-?
'/:.;.:
?:-'-"-.,.
-4t-'
;"'":::-•,
:..-•,
":;:½:
• .;;:;-..
";;:' :,;
:;'W'"-":/
- .'•... -..•!i'-•>•:;:½::;;I"
.. •.
.
...
....
Fig. 7. Venera 13 (side B) panorama in Viking lander surveymode perspective.
GARVIN ET AL.' VENUS SURFACEFROM VENERAPANORAMAS
3387
:.
Fig. 8. Venera14(sideA) panorama
in Vikinglandersurveymodeperspective.
extent and orientation than those at Venera 10. The overall
with the soil, and on the lander ring. The highest con-
roughness
of thebedrocksurfaces
at Venera13is comparable centrationof the pebblefractionoccursin an annulusaround
to that of Venera10, with perhapsa slightlylesseramountof the landerring. Many of the pebblesnearestthe landerring
are unburied,perhapsdueto effectsassociated
with the spacesurfacetexture and small-scaletopography.
Unlike Venera 10 thereis a significantcomponentof frag-
craft landing. However,most pebblesin other areas are at
mental material at the Venera 13 locality. The fragments at
leastpartially buried.
the siterangein sizefrom centimeterscaleto bouldersup to
0.5 m in length.The sizedistributionof fragmentsis clearly
bimodal with the pebblefraction (1-5 cm) dominatingthe
boulders(tensof centimeters)
in number.The albedoof most
of thefragments
of all sizesat Venera13is comparable
to that
of the unmantiedbedrockexposures
and is higherthan that of
the dark, fine materials that composethe soil. Unlike the
Venera9 locality,the blocksat Venera 13 are clusteredin
In terms of generalmorphology,the larger fragmentsare
predominantly
platyin form,haveangularto subangular
outlines,are oftenlayered,and displaya tendencyto fracturein a
planarmanner.Many of the largerfragmentsare strikingly
similar in form to those seen at the Venera 9 site. The larger
fragments
appearto be distributed
in clustersrelatedto bedrockexposures
at Venera13. Surfacetexturessimilarto those
visibleon bedrocksurfacesare typical of suchlarge fragments.
isolatedpilesratherthanprovidinga continuous
coverof the The smallerfragmentsare generallyin the pebblesizerange
surface.The smallerfragmentsare morecontinuously
distrib- and are more rounded in outline than the boulders, although
uted and can be found on top of bedrockexposures,
mixed a few are polygonalin outline like their larger counterparts.
Fig. 9. Venera14(sideB)panorama
in Vikinglandersurvey
modeperspective.
3388
GARVIN ET AL.' VENUS SURFACE FROM MENERA PANORAMAS
Fig. 10. Venera 13 (side A) polar gnomonic perspective(plan view) of near field. This is a projection from directly
above the spacecraft and provides minimum distortion in the immediate near field. As one moves farther from the
spacecraftbase,distortion increases,so that only the near field is presented.Seetext for further details.
Many of the smaller fragments are somewhat platy. The pebbles are not preferentially distributed in piles and do not
appear to relate to bedrock exposures.The ubiquity of the
smaller fragments in the near field of the panoramas and the
observation that a few of them were displaced up onto the
lander ring (10 cm high) suggest that spacecraft-landing-
induced effectsmay have locally modified the pebble distribution at the site.Away from the near field, it is apparentthat
the smaller fragments are well mixed with the lower-albedo
soils and are not as highly concentratedon the surfaceof the
soil. In this regard,they appear similar to the small fragments
in the interbedrock
soil areas at Venera
Fig. 11. Venera 13 (sideB) polar gnomonicperspective(plan view) of near field.
10.
GARVIN ET AL.' VENUS SURFACE FROM VENERA PANORAMAS
3389
Fig. 12. Venera 14 (sideA) polar gnomonicperspective(plan view) of near field.
Evidencefor in situ breakdown of large fragmentsand bedrock plates is widely observedat the Venera 13 site. In certain
cases,several fragmentscan be pieced together into a single
larger one (Figure 7, right-hand side; Figure 6, left-hand side).
This "jigsaw puzzle" effect was observedto a lesserdegree at
the Venera 9 locality [Florensky et al., 1977c]. A few partially
buried rocks appear to be significantlyinclined relative to the
plane of the surface,as was observedat Venera 9. At least two
layers can be discerned in several of the larger blocks, but
layering cannot be observed in the pebble-sizedfragments,
possibly because the pebbles are derived from single,
centimeter-thick layers [Krumbein and Sloss,1953]. Several of
the smaller fragmentsdisplay curvilinear outlines.
The centimeter to meter scale roughnessof this locality is
Fig. 13. Venera 14 (sideB) polar gnomonicperspective
(plain view)of nearfield.
3390
GARVIN
ET AL.' VENUS SURFACE FROM MENERA PANORAMAS
GARVIN ET AL..' VENUS SURFACEFROM VENERA PANORAMAS
TABLE
Site
3.
Observed Characteristics of Venera Lander Sites
Bedrock
Venera 9
3391
No unambiguousevidencefor bedrock exposure.
Fines/Soil(< 1 cm)
Fragments(> 1 cm)
Abundanceof angular to subangular
layeredand platy blocksin the 5-70
cm range.
Severalblockshave elongate,rounded
ridgesand other undulatory surfaces.
Apparentbimodal distribution(fines
below limits of resolution, coarse,
•1 cm).
Few intermediatefragmentsbetween
fines and 10-cm blocks.
Distributed between blocks, little evi-
Someblockspolygonalin outline;
someare steeplyinclinedrelativeto
dence of fillets around blocks.
horizon.
Finer fraction (1-5 cm) distributedin
interblock
Venera
10
Covers 40-60%
of surface.
Exposedas semicontinuous,
generally
fiat, subroundedto polygonal
patchesup to severalmetersin
width.
Surfacerough; in near field, 5-10 cm
of topography,up to a meterin
background.
Surfacetextureis pitted and alsocontains a cuspatescarp.
Linear and orthogonalfractures.
Venera 13
Covers 20-50%
of surface.
Exposedas semicontinuous
generally
fiat polygonalto subrounded
patches.
Surfacerough in near field, bedrock
plateedgesand surfaceshows5-10
cm of topography;pits and shallow
linear depressions.
Severalrounded,elongate,and cuspate scarps.
Linear fractures.
Surfacehasa somewhatlayeredappearance.
areas.
Only a few discretefragments > 5 cm.
Locatedin areasdominatedby fines,
not on bedrock.
Visiblefragmentsin soil gradeinto
roughnessat the scaleof resolution
in intermediate
and far field.
Larger fragments are angular to subangular, layered and platy; locally
distributed in patches associated
primarily with bedrock. Many
fragment boundaries can be related
to adjacent bedrock fractures.
Smallerfragmentsare located on and
within soil/finespatchesand only
occasionallyon bedrock.Occur in
two modes: 1) in an annulussurroundingthe landerring. The most
roundedparticlesoccurhere; fragmentslie on top of soil layer; 2) in
soil patchesbetweenbedrockexposures.Particlesmostlypartly
Finesdistributedin extensivepatches
in low areasand in small patches
on bedrock surfaces.
Fines lower albedo than bedrock.
Finesgradeinto smallfragmentsin
size.
Finesdistributedin extensivepatches
betweenbedrockexposuresand in
local small patchesin bedrockpits
and depressions.
Fines lower albedo than bedrock.
Bimodal distribution ?
Soil occurson surfaceof lander ring
on both sidesof spacecraftand on
lens cover.
buried.
Venera 14
Covers almost 100% of surface.
Exposedas continuousareasof interlocking,generallyfiat, polygonalplates.
Surfaceis rough at scaleof centimeters.
Surfacestructuredominated by subhorizontal to horizontal layered
plateswith thicknesses
of several
centimeters;somelayersshowdifferent albedo,with uppermost
layersdarkest;uppermostplate in
near field has hole or window re-
vealingunderlyinglayer; somesurfacesublayersshowtonguelike
overlaps.
Surfacetexturesincludepitting, waviness,and elongate,cuspatescarps.
Abundant linear and polygonalfrac-
Only a few discreteblocks > 10 cm.
One 50-cm block with layered/striated
texture.
Fragmentsare angular to subangular;
severalcan be geometricallyfitted
into adjacentbedrock.
In far field, fragmentsappear in local
patchesbetweenextensiveflat platy
bedrockexposures.
In near field,smallerfragmentshave
two modesof occurrence:(1)in depressionsand fracturesin bedrock,
and (2) distributedaround lander
ring on arm side of spacecraft.
Distinct paucityof finescomparedto
other sites.
Some local accumulations
in fractures
in bedrockand in front of spacecraft on arm side.
Soil occurson surfaceof lander ring
only on arm sideof spacecraft.
tures.
most strongly influencedby the accumulationsof larger fragments and the bedrock exposuresthat are most inclined relative to the flat surface.In general, the bedrock topography
appearscomparableto that of Venera 10.
The fine materials at Venera 13 are generally lower in
albedo than any of the other materials at the site and are
distributed in soil patches between bedrock exposures,as is
the case for the Venera 10 site. In addition, fine materials have
been depositedin depressionon bedrock surfaces.The edges
of bedrock exposuresthroughout the landing site are sometimes diffuse,suggestinga cover of soil on top of such bedrock. It is clear from the panoramasof the Venera 13 site that
the fine materials ( < 1 cm) making up the soil patches are
variable in size. Fine materials
are also observed on the lander
3392
GARVIN ET AL.: VENUS SURFACE FROM VENERA PANORAMAS
ring on both sides of the spacecraft,and a change in the
accumulationof dust on the lander ring as a function of time
on the surface of Venus was also reported [Selivanovet al.,
1982]. The fineson the spacecraftlanding ring probably representthe dust fraction of the fine materialsand are likely to be
< 100 #m (0.1 mm) in diameter [Garvin, 1981]. A few pebbles
can also be observed on the lander ring (Figure 7). These
fragmentsare likely to have been transportedto their present
positionby meansof landing-inducedeffectssuchas turbulent
eddies.This same effect may have caused transport of small
Veneras 10 and 13 to a host of polygonal fractures which
break up the surfacebedrock into smaller in situ plates. In
somecases,fracturesappear not to extend through the uppermost layer. The extensivepolygonal fracttire patterns at the
scaleof tens of centimetersare unlike the more widely spaced
fracturepatternsof Veneras10 and 13. They may, however,be
the type of fracturingthat would aid in the productionof the
jigsaw-puzzle-likeexposuresat Venera 13 and the extensive
polygonalblocksobservedat Venera9.
There are extremely few discretefragmentslarger than 10
fragments
ontothesoilandbedrock
surfaces.
cmin diameter
at theVenera14site.of thefewfragments
In summary, (1) the Venera 13 site is characterizedby a
fractured,somewhatplaty bedrocksurfacevery similar to that
observedat Venera 10 and a bimodal distributionof fragments, (2) the larger fragments are concentrated in local
moundsand are generallysimilar in morphologyto fragments
observedat the Venera 9 site, and (3) dark, fine materials
mixedwith smallfragmentsoccurin zonesseparatingbedrock
exposures,as observedat Venera 10.
that can be identified,most are platy, angularto subangularin
outline, and variable in albedo. One 0.5-m-long tabular block
in the near field displaysa layered or striated surface.In some
cases,the smaller fragmentscan be geometricallyfitted into
adjacent bedrock. In general,fragmentsappear to cluster in
local patches between platelike bedrock exposures.This is
Venera
14
similar to the rock clusters observed at Venera
13. In the near
field, pebble-sizedfragments occur either in depressionsor
fracturesbetween bedrock plates or in a diffuse zone around
the lander ring on the penetrometer side of the spacecraft
(Figure8).In thefar'field,fragments
appear
predominantly
in
The most striking feature of this locality is the predomilocal patchesbetweenextensiveflat platy bedrock exposures.
nance of bedrock,which occursover nearly 100% of the surIn one'case,a fragmentdislodgedfrom bedrockhas exposeda
face visiblein the panoramas(Figures8, 9, 12, and 13). Dishigh-albedosurfaceon the underlyinglayer and the underside
crete fragmentsand some fine materials at the boundariesof
bedrock plates can be recognizedamidst the continuousexposuresof platy and layered bedrock. There are no continuous soil patchesmantling the bedrock exposuresas seen at
Veneras10 and 13. There are no extensiveblockycoveringsas
seen at Venera 9 and no block clusters as seen at Venera 13.
The most abundant bedrock exposuresat Venera 14 are
typically interlocking subhorizontalpolygonal plates which
have variable surface texture. Bedrock surface textures include
shallowcuplike depressions
or pits, elongatedepressions
resemblingflutesor grooves,cuspatescarpssomewhatsimilarto
those at Venera 13 in morphology,wavy and linear undu-
of the dislodgedfragment.
There is a distinct paucity of fine-grained material at the
Venera 14 site relative to other sites.Low-albedo fines appear
to be preferentiallydepositedin the linear and polygonal fractures which define bedrock plate boundaries.These fine materials have a grain size lessthan the resolutionof the camera
and probably representa dust fraction,similar in propertiesto
the finest materials
at the other Venera sites. Some of this dust
material was perturbed by the spacecraftlanding enough to be
carried
at least
10 cm off the surface and onto
the lander
impact ring.
In summary, the Venera 14 locality is characterizedby (1)
lations, and linear fractures often filled with low-albedo fine
the dominance of continuous,flat, multilayered bedrock exmaterials.Severalareas of more irregularly textured bedrock
posures,(2) a paucity of fines and fragments,and (3) the varioccur within the regionsof platy bedrock.In some casesthe
able albedo of bedrocklayerswith the uppermostlayer in one
irregulartextureis dominatedby small lobate or tonguelike
area having a low albedo.
layers and a somewhatropy texture (Figure 8, right-hand
side).In other casesthe irregulartextureappearsto be a series
of small,slightlydisruptedplatesoccurringbetweenthe larger,
more continuousbedrockplates(Figure9, left-handside).The
extensivebedrock plates at Venera 14 share many of the
characteristics
of bedrockexposuresat Veneras10 and 13.
One of the mostdistinctiveaspectsof the bedrockat Venera
14is the presence
of horizontalto subhorizontal
layeredplates
with thicknesses
of severalcentimeters.
Layer thicknesses
are
variable, ranging from a few to tens of centimeters.Sublayeringcan alsobe recognized.
The mostprominentexample
of layeringoccursin the middleleft of Figure 9 wherea lowalbedo layer clearly overliesa higher-albedolayer. A small
hole in the low-albedolayer revealsthe presenceof the underlyinglayer and indicatesthe thinnessand continuityof the
upperlayer.The lateral continuityof individuallayersis diffi-
4.
SUMMARY AND DISCUSSION
The following points summarizethe geologicalobservations
derived from the Venera panoramasat Veneras9, 10, 13, and
14 (this work and Florensky et al. [1977a, b, c, d, 1982a, b,
1983a, b, c]) and presentadditional observationswhich might
be relevant to the interpretation of geologicalprocessesoperating at eachsite.
Bedrock
Panoramasof the sitesrevealthat bedrockexposuresdominate the Venera 14 site and compriseat leasta third (Venera
10) to one half (Venera 13) of two of the other sites.This is
truly remarkableconsideringthat the landingsitesare separated by several thousand kilometers. On the moon, bedrock
cult to determine, but several extend over several meters disexposuresare almost unknown, and on earth they are relatance.In numerouscases,bedrocklayersare observedto over- tively rare. On Mars, they are also likely to be uncommon
lap, particularlyin the more irregularlytexturedbedrockre- [Kieffer et al., 1977], although somebedrockappearsto be
gions, where tonguelike overlaps are sometimes observed exposedat the Viking lander 1 site [Binder et al., 1977; Mutch
(Figure 9).
Fracturesin the Venera14 bedrockare abundantand range
from several extensive linear fractures similar to those seen at
et al., 1978].
The surfacetopographyrangesfrom severaltensof centime-
ters (Veneras 10 and 14) to possiblyseveralmeters (Venera
GARVIN ET AL.: VENUS SURFACE FROM MENERA PANORAMAS
13). The surface morphology of the bedrock outcrop shows
multiple plates with horizontal dimensionsof centimetersto
meters often bounded by vertical fracturesand having a surface texture which includeslayers,lobes,pits, flutes,and small
arcuateridges.The centimeterscalelayeringobservedat Veneras 14, 13, and 10 is discontinuousand closelyrelated to the
platy nature of the surface.Some layersappear to be truncated by others at low angles,but systematic,well-developed
cross lamination is not observed.Potential processesto account for the layering include (1) depositional(sedimentsof
erosionalor pyroclasticorigin, [see Florenskyet al., 1983c]),
(2) duricrust and/or autometamorphism[Florensky et al.,
1983c],(3) sheetingdue to unloading,and (4) lava flow due to
3393
ing bedrock and that most of those observedin the images
have not been subjected to extensive transport. The similarities of Venera 14, 13, and 10 fragmentsto those observed
at Venera9, whereno bedrockis seen,stronglysuggest
that
the bedrock in the Venera 9 region is similar to that at the
other Venera sites. In addition, the angularity of Venera 9
fragmentsindicates that the bedrock source is in the near
vicinity of the landing site [Florenskyet al., 1977a,b, c, d].
Fines
The fine materials (< 1 cm) have a low albedo and are
abundant at Veneras9, 10, and 13. They occur evenlydistributed betweenblocks (Venera 9), as irregular patchesin low
primary flows,flow dynamics(lobes,deformationof plastic
areas betweenbedrock (Veneras9 and 10), and in pits and
surface, crystal segregation,etc.), cooling history (cooling
patcheson bedrocksurfaces
(Veneras10 and 13).There is no
units),or somecombinationof theselava flow mechanisms.
evidencefor major transportof finesby atmosphericprocesses
Fractures are apparent in bedrock at all sites. They are
(ripples,scour,wind tails,etc.),althoughsuchtransportcannot
vertical, form orthogonal and polygonal patterns, and, in at
be ruled out. Finesmay be locallyderivedby the chemicaland
least one place at Venera 14, do not penetratethe uppermost
physicaldegradationof bedrockand fragments.The lack of
layer. No evidencefor lateral offsetis seen.Potential processes
fines at Venera 14, the landing site with the least degraded
to account for the fracturesinclude (1) landing-induced(apbedrock characteristics,and the abundance of fines at Veneras
pears unlikely becauseof the pervasiveness
of the fractures
10 and 13, where bedrock is more degraded,are consistent
and the angularityof the blocks),(2) thermal cyclingand deswith the local derivation of a soil component.
iccation(appear unlikely at presentbecauseof relativelyconstant surfacetemperaturesand lack of water (although these ContinuityBetweenLandingSites
may be candidates in previous periods of the history of
The Venera sites are separatedfrom each other by thouVenus)), (3) volatile loss or degassingof ash layers, (4) lava
sandsof kilometers(Plate 1), and the four sitesare spreadover
flow cooling (deformationof surfaceplates and longer-term
an area comparableto the continental United States, the
cooling and production of joints), and (5) tectonic(fractures
Tharsis region on Mars, or the largestof the lunar maria,
associatedwith stressreleaseor active deformation).
Oceanus Procellarum. The similarity of bedrock, fragment,
Although the bedrocksurfaceshave distinctivemorphologic
and soil characteristicsat the sitesis extraordinary. Any profeatures,there is no compellingevidencefor the presenceof
cessproposedto accountfor the formationof bedrockmust
clastsor grains distinguishablewithin the bedrock outcrops.
operateoverextensive
regions,at leastin the Venusianplains.
Any clasts,grains,or phenocrystswould either be below the
limits of resolutionor indistinguishable
from the matrix. If the Albedo Characteristics and Variations
fragmentsseenat the Venera siteswere incorporatedinto a
The albedo of the materials at the Venera 9 and 10 sites is
depositand lithified into bedrock,it is likely that they would
,
be observed
because of their
size and distinctiveness.
This
low to verylow,comparable
to basalt[Florensky.et
al., 1977a,
b, c, d]. Veneras 13 and 14 appear to have a similar low
albedo. At Venera 14, the uppermostcentimeter-thicklayer
(Figure9) in one areais characterized
by a lower albedothan
Venera sites.
underlyingbedrockand appearsto be the only layer with a
distinctivelydifferentalbedo.On the basisof the presenceof
Fragments
the "window" in this unit and the nature of the layer edges,
Although some fragments(> 1 cm) are visible at all sites, the layerappearsto be undergoing
erosion.SinceVenera14 is
the abundanceis variable from site to site and within a given the leastdegradedsite, this low-albedolattermay represent
site. Fragmentsdominate the Venera 9 area and are sparsely the uppermostlayer or layers of fresh,relatively uneroded
arguesagainstthe simpleconversion(e.g.,lithification)of observederosionalproductsinto the type of bedrock seenat the
distributed
at Veneras 14 and 10. At Veneras 13 and 14 there
is evidencefor redistributionof fragmentsaround the lander
ring from the influenceof the spacecraftdescentand landing.
At Venera 14, additional fine fragmentsoccur in fracturesin
the bedrockand in low complexareasbetweenmajor bedrock
plates.Small fragmentsoccur within the soil patchesbetween
bedrock exposuresat Veneras 10 and 13. Larger fragments
can often be fitted into adjacentbedrock,as at Venera 14, or
form small mounds where the fragmentsoccur in a jigsaw
puzzle fashion,as at Venera 13. In the latter case,the fragmentsappear to have formed in situ from bedrock.
The vastmajority of the largerfragmentsat the Venera sites
are platy, angular to subangular,showno evidencefor discrete
grains or clasts,are textured, and occasionallyare layered.
The similarityof fragmentsfrom site to site and the similarity
to bedrock characteristics is striking. These similarities
stronglysuggestthat the fragmentsare derivedfrom underly-
bedrock.
In other layers at Venera 14, displacedblocks exposetwo
typesof surfaces.One dislodgedblock broken apparentlyat
an angleto layering(Figure8, right center)revealsthe internal
structure of a bedrock unit and shows the albedo to be com-
parableto the adjacentsurface.Elsewherein the samepanor-
ama(Figure8, leftside)twoblockshavebeendislodged
parallel to layering and at least one has been overturned.These
surfacesdisplay a higher albedo than surroundingbedrock
surfaces.If the three fragmentswere dislodgedby spacecraft
landing,then thereis someevidencefor a higheralbedoalong
planesseparatinglayers.If the fragmentsdislodgedat different
times,then surfacemodificationeffectsmay be important (e.g.,
freshsurfaceshave a higheralbedobut have the albedoloweredby exposureto the Venusianenvironment).
In eithercase,
theseexamplesappearto differ from the low-albedolayer observedon the other sideof the spacecraft.
3394
GARVIN ET AL..' VENUS SURFACEFROM MENERA PANORAMAS
CompositionalInformation
Gamma ray spectroscopy
experimentson board the Venera
9 and 10 spacecraftprovidedinformation on the K, U, and Th
contentsof materials at the sites.Surkovet al. 1-1977a]and
Florenskyet al. 1-1977c,d] compare the valuesat Veneras9
and 10 with terrestrial basalts. X ray fluorescencespectrometer experimentson board Veneras 13 and 14 analyzed
material drilled from below the lander ring and transported
inside the spacecraft.Venera 13 results suggesta highpotassium basalt composition and Venera 14 a tholeiitic
basaltcompositionl-Surkovet al., 1983, 1984; Barsukovet al.,
1982].
exposures.
At leastlocal transportis requiredto concentrate
the soilin lows.Examinationof the topographyof the essentially soil-free Venera 14 site showsthat if soil were to fill the
low-lyingareas,the sitewouldbe remarkablysimilarto Veneras13 and 10 (compareFigures4 and 5 to Figures7 and 8).
On the basisof the stateof degradation
(sharpness
of features,
abundanceof soil,etc.)the Venera 14 siteis believedto be the
leastdegradedand Veneras10 and 13 to representmorede-
gradedbedrockterrain.The Venera9 site is anomalously
blockyin comparisonto Veneras10, 13, and 14 and doesnot
appearto fit in a simpledegradationsequence
becauseof the
angularnature of its blocks.The angularityand freshappearanceof the bedrockat Venera 14, combinedwith the lack
Material Properties
of soil cover,suggestthat the surfacemay be geologically
Material propertiesof the substratecan be measuredand
estimatedfrom a variety of observations.At Venera 10 the
young or that erosionrates are low.
gammaray densitometer
yieldeda densityof 2.8 _ 0.1 g/cm3
Comparisons
to OtherPlanetarySurfaces
l-Surkovet al., 1977b] for bedrock, while observationsof the
On the moon, impact-generated
regolith of severalmeters
dominatesthe surface.Only at the Apollo 15 site
influenceof droppingthe 2-kg gammaray spectrometers
(on a thickness
of
rock at Venera9 and bedrockat Venera 10) indicatethat the alongthe edgesof Hadley Rille havesurfacephotographs
materialis hard competentrock l-Florensky
et al., 1977c].Esti- bedrockbeen obtained.In this case,an 8-m-thickoutcrop
matesof the dynamictensilestrengthof the Venusiansurface with 12 exposedlayersof basalticlava flows were photoat Veneras9 and 10 [Keldysh,1979] indicatea wide range graphedalongthe far wall of the rille, approximately1.5 km
extendingfrom 40 to 300 bars. This range includesmaterials away.Severalof the moremassive
layers(1-3 m thick)contain
rangingin tensilestrengthfrom weldedtuffs (tensof bars)to less well-definedinternal layering or parallel banding.A
massivebasalts(over 200 bars).Values lessthan 10 bars are numberof thinnerlayerslessthana meterthickoccurtogethtypical of soils.At Venera 13 the penetrometerappearsto er and separatethe thickerlayersfrom eachother.The thinner
have impacted a bedrock outcrop or blocks. Surkovet al. layersweather out distinctively.Vertical to near-verticalfrac[1984] report dynamictensilestrengthsof 2.6-10 bars based turesare observed.Somefracturescut throughboth massive
on their interpretationof the penetrometermeasurements.
At and thin layers,whileothersterminatewithin the layeredseVenera 14 a similarmeasurement
in bedrock(perhapsinflu- quencesometimesat a thinnerlayer. Other outcropsdisplay
encedby the lenscoveringwhichfell beneaththe penetrom- discontinuous
thin layeringor parting(averaging
about0.3 m)
eter) was 65-250 bars. On the basisof the dynamicsof the and rare columnarjointing l-Swannet al., 1972; Howard and
impactof the landingmodule,the valuesof 4-5 bars [Surkov Head,1972].Resolutionrestrictions
precludeestablishing
the
et al., 1984]reportedfromVeneras13 and 14 weresuprisingly presence
or absenceof centimeterscalelayering.
On Mars, severalprocesses
have apparentlybeenactivein
similargiventhat Venera13 appearsto havelandedlargely
on soil and Venera 14 on bedrock. If the fragmentssur- productionof the Viking 1 and 2 landscapes,
includingvolroundingthe landerringwe•'elargelybrokenby the spacecraft canism,impact,thermalcycling,catastrophicflooding,and
I-Mutchet al., 1976a,b; Binderet al., 1977;
landing,then Garyinet al. 1-1983b]find that the dynamicten- eolianmechanisms
silestrengthof the fragmentsourcerock is in the rangeof tens Garyin et al., 1981a, b]. Some areas of bedrock are visible at
of bars and no greaterthan 100 bars.If the fragmentswere Viking 1 in midfieldviewsl-Mutchet al., 1978]. Theseare
merelydisplacedby the spacecraftlanding,then 100 bars is a interpretedto be exposuresof the Chryse basin lava flows
lower limit. Valueslessthan 100 bars are typicalof weakly [Binderet al., 1977].The midfieldviewsshowa platy surface
induratedrock material,while higher valuesrepresentmore interrupted by linear scarpsgiving the bedrock exposurea
highly consolidatedor crystallinerocks [Nafe and Drake, steplikeappearance.The linear scarpsare interpretedto be
1968]. It is important to note, however,that impact-related the boundariesof steeplydipping fracturesin the lava flows
fragmentationand the possibleeffectof weatheringcouldact [Binder et al., 1977]. A diversepopulation of blocks is obto decreasethe strengthof near-surfacelayers.It is therefore servedat both sites.The two Viking lander sitesappearto be
unclearwhetherthe strengthof the sampledregionis typical much more variable within a givensite and betweensitesthan
of Venusianbedrock.The abovematerial propertiesmeasure- do the Venera 10, 13, and 14 sites.At Venera 9 the 35% block
cover is more extensivethan either of the two Viking sites
[Garvin et al., 1981b].
Modification Processesat Venera Sites
On earth, multiple geologicprocessescombine to produce
A numberof factors(fragments,soil, roundingof edges, complexgeologyat the scaleof surfacepanoramasl-Garvinet
exposure of layers, presenceof an apparently erosional al., 1981a, b; Garyin, 1982]. Some environments on earth,
window,pittingof surfaces,
etc.)pointto the probabilitythat however,are regionallyand/or temporallycontinuousenough
the Venerasitesare presentlyundergoingerosionof bedrock to produce wide expansesof terrain dominated by a single
layers.At the sametime, depositionof fragmentsand fine process.These areas/environmentsinclude desert sand seas,
materialsis taking place.The lack of any featuresrelated to areassuchas Mount St. Helensdominatedby pyroclasticash
atmospherictransportof material (ripples,dunes,wind tails, flow/fall, regions such as Hawaii dominated by basaltic lava
scourmarks,etc.)suggests
that theseprocesses
are not domi- flows,the sedimentarybasinsof the deep sea,and others.The
nant in the panoramaareas.The dark soilsmay thusbe lo- strikingsimilarityof the Venerapanoramasto eachother and
cally derived from the bedrock materials. At the Venera 10 their separation distancesmeasuredin thousandsof kilomeand 13 sites, soil is concentrated in lows between bedrock ters argue for the dominanceof either a singlegeologicproments should thus be considered a lower limit.
GARVIN
ETAL.'VENUS
SURFACE
FROM
VENERA
PANORAMAS
Pahoehoe lavas (flood basalts)
Lower Yakima Flows (Diery-McKee, 1969)
Elephant Mountain Flow (Schmincke 1967)
Vesicular top
sheeting
Vesicular
Buckled top
zone
upper colonade
Entablature
Platy jointing
Vesicular
zone
horizontal
tier
Abrupt zone
Fan jointing
Small columns
Entablature
hackly jointing
Gradational
Vesicle
Hackly to
brickbat joint•ng
zone
Undulating columns
blocky jointing
cylinders
Basal colonade
Colonade
Pipe vesicles
Platy jointing
Flow
direction
P•llow-palagonite breccia
Flow
direction
Aa to Blocky lava flows
Aa basalticandesite
Extruded
Blocky latite
Obsidian
lava
Blocks
Scoria
Spinose
Abrupt
Platy joint•ng
Gradat•onal
Blockyto columnar
Flow-layered
jointing compact
curved columns
Breccia
(blocks and pumice)
Breccia
lens
interior
Contorted layering
Platyjoint•ng
Abruptscoria,
Abrupt
breccia
breccia
Abrupt
breccia
•] Flow
direction
½-'-]
Flow
direction
••] Flow
direction
Fig. 14. Cross-sectional
features
ofterrestrial
lavaflows[afterHammond,
1974].Notebuckled
topandplatyjointingof
pahoehoe
floodbasalts.
Seetextfor comparison
withfeatures
visiblein Venerapanoramas.
and reflectivityvaluesof the regionssurrounding
cess(suchaslavaextrusion)
or the presence
of an atmospheric roughness
environmentthat woulddispersematerials(suchas sediments each of the Venera sites as measuredby the Pioneer Venus
radar experimentat approximately100-kmhorizontalscales.
or pyroelastics)
in a widespreadand evenmanner.
Theyfind a positivecorrelationbetweenradar roughness
and
RegionalNature and GlobalExtent
roughness
as observedin the panora.mas.
The smoothestsite
for the planet.Thus
The Vcnera 9, 10, 13, and 14 spacecraftlanded in the Beta- (Venera14) is near the mean roughness
PhoeberegionEBazilevski
et al., 1982] at elevationswithin a largeareasof Venusmaybe evensmootherat thisscalethan
rangeof 2 km abovemeanplanetaryradius(Plate1 andTable the Venera 14 region.Reflectivityvalues[Pettengillet al.,
1). On the basisof earth-basedradar imagesand altimetry, 1982]canbe usedto relatedielectricconstantto bulk density
Saundersand Malin [1977] and McGill et al. [1981] have [Krotikov,1962;McGill et al., 1983].Model densitiesfor the
interpretedthe Beta regionas a riff structurepopulatedwith Venera9 and 10 regionsare 1.9 g/cm3, muchlessthan the
shield volcanoes such as Rhea and Theia Mons. Recent Are2.8 + 0.1 g/cm3 determined
for bedrockat the Venera10 site
that the regionalsite
cibo radar backscatterimages(1.5-2.0 km radar resolution) [Surkovet al., 1977b].This suggests
(D. Campbellet al., unpublishedmanuscript,1983)strongly values(• 300km2 areas)are loweredfromthe bedrockvalues
supporta volcanicoriginfor thesefeaturesand haveshown by the inclusionof the lessdensesoil componentobserved
that flowlike structures extend for a distance of more than 400
overlargeareasin the panoramas.Venera14, the sitewith a
km from the summit area of Theia Mons, down the flanks of
Beta Regio. Garyin and Head [1983] have examinedthe
paucityof soil,hasa modeldensity
of 2.4g/cm3 for thesurrounding
region.Thus2.4g/cm3 maybea lowerlimitfor the
3396
GARVIN
ET AL.' VENUS SURFACE FROM VENERA PANORAMAS
Fig. 15. Lava flow exposuresfrom the Snake River Plain (from Greeleyand Kin•t [1977]; photosby J. King and J.
Karlo). A blockytaluspile is exposedat the edgeof a seriesof lava flows.Suchblockysurfaces,
morphologicallysimilarto
Venera 9, are commonalong vent and rille walls. Elsewherein the image, analogsto bedrockplates and polygonal
fracturesobservedin Venera panoramascan be seen.
rocks at Venera 14 if any soil is exposedin the approximately
cross bed boundaries..... and pinching out of beds" [Florenskyet al., 1983c].
Venera 9, 10, 13, and 14 range are very common on Venus,
On the basisof our assessment,
two possibilitiesseemmost
although areas of higher and lower valuesexist.
likely: (1) homogeneouslayered tephra, and (2) thin, platy
basalt flows. Previous analysesof pyroclastic volcanism on
Venus [Garvin et al., 1982] have demonstratedthe theoretical
5. INTERPRETATION
requirementfor unusuallyhigh volatile contents(> 2 wt %) in
Interpretation of the geologicalprocesses
responsiblefor the magma in order to produceexplosiveeruptionsin the present
featuresobservedin the Venera panoramasmust accountfor
Venus environment. Thus, in this analysis we pursue the
the range of data outlined above,specificallythe extremesimi- second hypothesis,that is, that the bedrock originated from
larities between sites,the compositionaldata, and the platy surfacelava flows. We thereforeconsiderthe possibilitythat
surfaces,layers, fractures,and structuresof the bedrock units. the bedrock at the Venera 10, 13, and 14 siteshas originated
The soil componentat thesesitesis largely below the limits of
by the first of the processessuggestedby Florensky et al.
resolution. For this reason and the fact that physical and
[1977c]. Specifically,we believethat the broadly platy nature
chemical weathering processeson Venus are poorly under- of outcropsat Veneras 10, 13, and 14 may be comparableto
stood, we emphasizehere the interpretation of bedrock units the rolling and undulatingnature of terrestrialpahoehoeflows
and fragments.
causedby the formation and deformation of a semisolidcrust.
On the basisof observationsat Veneras9 and 10, Florensky The rougherinterplate areasappear analogousto deformation
et al. [1977c] outlined six possible origins for the bedrock within and between plates to produce festooning and ropy
outcrops,fragmentsand fines:
texture, and pressure ridges with associatedjumbled crust,
squeeze-ups,and small lava tongues (see, particularly, the
1) surfacelava extrusion;2) igneousintrusion later exposedby
middle
right-hand portion of Venera 14 (A), Figures 2 and 8).
erosion;3) pyroclasticfall; 4) impact lithification; 5) sedimentary
The jigsaw puzzle nature of the blocky mounds at Venera 13
rock lithified at depth and later exposedby erosion;and 6) lithification (or metamorphism)of loose material by atmospheric
suggestssmall platy pressureridges which have been someaction at the surface.
what eroded (Figure 7). The extensivelayering observedat the
site is unlikely to be due to individual primary flows because
Florensky et al. tentativelyconcludedthat "Hard material is of the thinness of layers. Calculations on lava flow cooling
occasionallyformed at the surface,either by lithification [of
efficiency in the present Venus environment [Wood, 1979;
fines] through atmosphericprocessesor by volcanic falls." Head and Wilson, 1982; Garvin et al., 1982] indicate that thin
Analysisof the Venera 13 and 14 panoramasby Florenskyet flows on the scale of observed layering would not be wideal. [1983c] led them to conclude that the bedrock is of sedispread. The layering is interpreted to be analogous to that
mentary origin, depositedin the past as clastic sediments layering commonly observedin terrestrial lava flows, which is
(either erosional productsfrom highlandsor pyroclasticde- a combinationof an upper thermal boundary layer (crust)and
posits)which may have been lithified into layers by a "duri- horizontal sheetsformed generally parallel to the top of the
crust" phenomenon.A major factor in this interpretation is flow due to cooling and shearingduring flow emplacement.
the observedlayering,its thinness,"fracturingwhich doesnot
Cross sectionsof a variety of lava flows (Figure 14) show the
300-km2 area surrounding
the site.Reflectivityvaluesin the
GARVIN ET AL..' VENUS SURFACE FROM VENERA PANORAMAS
3397
Fig. 16. Exposureof a slab pahoehoeflow surfaceabout 4000 years old in the Snake River Plain (from Greeleyand
King [1977]; photosby J. King and J. Karlo). Abundantfracturedplatesare reminiscentof bedrockexposuresat the
Venera 10, 13, and 14 sites.
nature and distribution of various typesof horizontal layering
(platy jointing, sheeting,and flow layering).Macdonald[1972,
p. 93] describesthe formation of sheetsin block lava flows,
noting that the
than the presentterrestrialsubaerialenvironment.The high
Venusianuppercrustaland surfacetemperatures
would favor
greatereffusionrates and lessefficientlava cooling,both of
which are factors that would produce long extensiveflows
relative to comparable terrestrial eruptions [Wood, 1979;
moving liquid higher up tendsto separateinto a seriesof sheets
slippingover each other like a seriesof cardsin a deck when the
deck is bent. The samesort of motion (laminar flow) is presentin
aa and pahoehoeflows, but the separationinto sheetsshearing
over each other is lesspronounced.The movementof the sheets
is predominantlynearly parallel to the underlyingsurface,and in
solidifiedflows the shearsurfacesare visibleas planesof separation (joints)essentiallyparallel to the top and bottom of the flow.
The sheetsmay be very thin. Sometimesthey are only a fraction
'of an inch thick, and then the lava resemblesthe platy sedimentary rock, shale.
(;arvin et al., 1982; Head and Wilson, 1982; Wilson and Head,
Macdonald further notes that occasionallyshear planes may
bendupward at the front or top of the flow.
Vertical fractures, or joints, are ubiquitous in lava flows
(Figure 14) and are due primarily to tensionalstressesassociated with volume reduction due to cooling. The nature of
jointing commonly changesat subunit boundaries,and vertical joints often stop abruptly at theseboundaries(Figure 14).
The patterns of joints may range from rectangular to polygonal and blocks derived from jointed flows are commonly
angular in form. The extensive vertical fractures seen at
Venera 14, and the shapeof bedrock exposuresat Veneras 10
and 13, are interpreted to be related to joint patterns. The
angularityof blocksvisibleat Venera9 mayalsobe relatedto
jointing.
Thus we find a number of strongmorphologicalsimilarities
between the bedrock and blocks at the Venera 9, 10, 13, and
14 sites and terrestrial
basaltic lava flows. We believe that this
interpretation based on morphologic characteristicsis supported by geochemical analyses indicating basaltic compositions,the low albedo of surfacerocks, comparisonto surface
imagesof outcropsof known (moon) or suspected(Mars) volcanic origin, the high density, the extreme similarity between
sites separatedby thousands of kilometers, and the strong
likelihood that extrusive volcanism has been a significant
mechanismof heat transfer throughout the history of Venus
[Solomonand Head, 1982; Morgan and Phillips, 1983], and in
the Beta-Phoeberegion [Saundersand Malin, 1977; McGill et
al., 1981; D. Campbell et al., unpublishedmanuscript,1983].
The presentVenus environmentis considerablydifferent in
terms of temperature,pressure,and atmosphericcomposition
1983]. Although many earth analogs [cf. Green and Short,
1971; Greeley,1974; Greeleyand King, 1977] can be found
which show similaritiesto the Venera panoramas (Figures 15
and 16), we are presentlyconcentratingon an analysisof the
flow and coolingbehaviorof lavas with compositionsof the
Venera site materials, under Venus conditions, in order to
provide a frameworkfor further investigationof terrestrial
analogsin the subaerialand subaqueousenvironment.
Acknowledgments.
The authorsaregratefulto SovietScientists
at
the VernadskyInstitute of Geochemistry(V. I. Barsukovand A. T.
Basilevsky)
and the Instituteof CosmicResearch(L. V. Ksanfomality)
in Moscow,who kindly providedthe Venera photographsand necessaryliteratureon the panoramiccamerasystemsusedin this study.
Sam Merrell producedthe transformedVenera panoramamosaics;
Jeff Tingle wrote most of the softwareusedto displaythe digitized
Venera photographs.The manuscriptwas preparedby Mary Ellen
Murphy. Helpful commentsand suggestions
by Richard Grieve,
Mark Cintala, Peter Mouginis-Mark, Robert Sharp, R. S. Saunders,
and Alan Peterfreundare gratefullyacknowledged.Duncan Chesley
of the Universityof Massachusetts
producedthe digital versionsof
the Veneraphotographs
usingan Optronicsscanner.
'Specialthanks
to Harold Masursky of the U.S. GeologicalSurvey for providing
Plate 1 and to R. Greeley of Arizona State University for providing
prints of Figures15 and 16. This researchwas supportedby NASA
grant NSG-7569 for which the authorsare most grateful. One of the
authors(J.B.G.) was supportedby a fellowshipfrom the William F.
Marlar
Memorial
Foundation.
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(ReceivedJuly 28, 1983;
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