Vol.
3,
No.
Geophysical
3
CHARACTERISTICS
Research
March
Letters
OF FRESH MARTIAN CRATERS AS A FUNCTION
COMPARISON WITH THE MOON AND MERCURY
Mark
J.
1976
OF DIAMETER:
Cintala
James
W.
Head
Thomas
A.
Mutch
Department of Geological
Sciences
Brown University
Providence,
Rhode Island
02912
Abstr.act.
Martian craters defined as fresh on
a more comprehensive analysis of the morphologies
the basis of morphologic parameters have been analyzed for the presence and abundance of various
morphologic features as a function of size.
Bowl-shaped craters
dominate the fresh crater
population below about 15 km. The onset of central peaks occurs at about 5 kin. Craters above
about 15 km often have terraced walls,
central
peaks, and h,,mmockyfloors; at diameters of 40 km
and greater, these features dominate fresh mar-
tian
crater
morphology.
Central
of fresh craters on Mars and to compare the characteristics
and size distribution
of morphologic
features of martian craters with those on the
Mmon and Mercury.
Based on criteria
presented below, 33,810
fresh craters were chosen from a population of
46,559 martian craters of all sizes and morphologies.
The data base consists of a catalog of
all craters visible on Mariner 9 A frames.
Cra-
peak onset
ter location,
rim crest diameter,
and a series
occurs at smaller diameters on Mars and the Moon
than on Mercury, and terrace onset occurs at similar diameters on the Moon and Mars, but at larger
diameters than on Mercury.
Since Mars and Mercury have a similar surface gravitational
accele-
of morphologic features,
as well as several other
parameters, are recorded for each of the craters.
The procedures for recording the data and the details
of the morphologic classification
scheme
are presented elsewhere (Arvidson et el.,
1974;
ration
Arvidson,
(greater
than twice that of the Mmon),
gravity-controlled
crater features should appear
at similar
diameters on the two planets.
However,
the
differences
in
onset
and
abundances
of
Definition
on the
Earth
than
on the
Moon, Mars,
as volcanic
parameters
have
of
Fresh
Craters
terized by rays, satellitic craters, radial rim
facies, a sharp rim crest, and terraces or a bowl
shapedepending
on size (PohnandOffield, 1970;
Recent space flights
to Mars and Mercury have
shown that cratering
is a significant
process on
these planets,
as well as on the Moon. While
fresh craters on the three planetary bodies and
the Earth show similarities,
differences
have
also been noted.
For instance,
the first
appearance of central peaks (Gault et a!.,1975;
meters
classified
Fresh lunar craters over several kilometers in
diameter have a crisp appearance and are charac-
duc tion
Smith and Sanchez, 1973) occurs at smaller
Craters
cen-
tral peaks and terraces
on Mars and Mercury indicate that processes other than gravitational
•ffects
may also be important.
Intro
1974).
on the basis of these morphologic
not been included in this study.
Arthur et el.,
1963; Wood, 1972; Smith and
Sanchez, 1973; Head, i974; Howard,1974; Pik___•e,
1974). Relative youth of craters is determined
both by crispness and stratigraphic relationships.
Fresh craters are of Copernicanage (with rays)
or Erathosthenian age (fresh morphologies without
dia-
rays) (Wilhelmsand McCaule•y,1971) and spanan
age range of about the last 3 billion years
(Head.,1974, Fig. 3). Large Irabrian-age craters
showonly slightly higher levels of degradation,
but pre-Imbrian craters are usually heavily degraded (.Head,1974). The freshest lunar crater
or
Mercury (Hartmann, 1973).
Causes for variation
in fresh crater morphology may be related
to
gravitational
differences
from planet to planet
(Hartmann, 1972) and their effects during crater
excavation
and modification
(Gault et al.,
1975).
Other variations,
such as impact velocity
(Wetherill,
1975) or substrate variations
(Head,
1976), may also be important.
Preliminary
information on the morphology of fresh craters has
class of Arthur et el.
(1963),
Class I,
is char-
acterized by craters with sharp rim crests, while
Class
rims.
II
craters have blurred or possibly broken
Class I craters
correlate
with craters
of
Copernican, Erathosthenian, and even Imbrian age
(C. A. Wood, personal communication). Fresh craters on Mercury show similar characteristics
and
correspond to Class I lunar craters (Gault et el.,
been presented for the Moon (Smith and Sanchez,
1973) and Mercury (Gault et el., 1975), based on
relatively
small
ter population.
samples of the total
fresh craPreliminary
observations have
also been made on martian crater morphology and
morphometry, but are also restricted
to small
samples of the total fresh crater population
1975).
Using similar criteria,
fresh martian craters
are defined as unmodified or nearly unmodified
structures which appear in one of three categories
(Hartmann,1972, 1973; Pike, 1971; Murrayet el.,
1971). The purposeof this paper is to present
Copyright 1976 by the AmericanGeophysicalUnion.
(Fig. 1): 1) deep, flat-floored, with terraced
walls; 2) deep, bowl-shaped,with terraced walls;
and 3) deep, bowl-shaped, with non-terraced walls.
117
,
Cintala
118
et
al.:
Characteristics
of
Fresh
Martian
Craters
......
.;.:,:
.•:•::•:•:•;•*.•`•h.:•`•:•.•<•:•:•:•:•
•&gu=e •.
•=esh •a=[•a• c=a[e=s cha=ac[e=•s[•c o• [he [h=ee [ypes described
d•e[er•
deep• bo•-shaped cra[er •&[h non-[erraced •a•s•
(DAS 08838839)
deep, bo•-shaped cra[er •th
[erraced •a•s
(DAS 08297879)• c) a 59 • d&a•e[er•
c=a[e=
•[h
[e==aced
•a•s
ß ..
ß
deep• •a[-•oored
(DAS 07506488).
The deep category is a qualitative
expression for
relative
crater depth and compares to other categories such as shallow and extremely shallow.
fresh bowl-shaped craters as a function of size
and Fig. 2b shows the percentage of fresh craters which are bowl shaped, as a function of size.
Details
Almost 100 percent of all fresh craters
less than
20 km in diameter are bowl shaped.
Over 98 percent of the total
bowl-shaped crater
population
of mDdified
martian
craters
are
described
elsewhere (Jones., 1974; Arvidson, 1974).
Of the
fresh crater population
thus defined,
over 98
percent have raised rims, while this feature
is
seen in less than 25 percent of the remaining
population
of non-fresh
craters.
In addition
to
the morphologic
crispness
of these craters,
a
relatively
young age is supported by superposition relationships.
Less than one percent
of
the fresh craters
defined on morphologic
grounds
have breached rims or superposed craters,
compared to 25 percent for the more highly degraded
craters.
In
a morphologic
sense,
the martian
fresh
cra-
ter class is approximately equal to Class I
lunar craters of Arthur et al.
(1963).
and 0ffield
of
on
This
Mars.
the
fine-textured
is
tions of Mariner
modification
of
a result
of
deposits
resolution
limita
•
9 A frames,
and some eolian
exterior
crater
deposits
as
(Soderblom et al.,
1973).
craters
appear to be as
fresh
fresher
about
4.2
to
4.4
on
above
about
of the crater interiors. On the Moon,this value
lies close to the beginningof the Irabrian Period
(Head,1974).
Characteristics
presence
of fresh
with
Bowl-Shaped Craters.
solution
limits
with diameters
This
same
of
Size
of
A frames.
Craters
effect
accounts
for
a de-
crease in apparent abundance of bowl-shaped craters at diameters less than 3 km (Fig. 3).
It
is likely
that many of the bowl-shaped craters
here
classified
of degradation
as
present
would
show
in higher-resolution
a reclassification
from fresh
fresh
of
some effects
pictures,
some bowl-shaped
Fig.
Central peaks are seen in 685
in Fig.
2d.
However, their
above
10
km until
between
60
over
and
half
100
of
the
km contain
peaks.
These
features
not
found
are
are seen
diameters
at
in
483
be-
fresh craters between10 and 20 kmdisplay terraces but the proportion of terraced craters increaseswith increasingcrater size until 100
of the craters
over
50 km diameter
have
hummocks.
In
the
in flat-floored
lunar
case
floor
hum-
fresh Copernican-and
and are seen predomin-
craters
over 15-20 km in
diameter,
although
they do occur at lower diameters (Pohn and Offield,
1970; Smith and San-
chez, 1973; Head, 1974; Cintala
floor
kilometer
hummocks are
in diameter,
and Head, 1976).
generally
less
than a
which is approximately
the resolution
of Mariner
9 A frames.
On Mars,
floor hummocks are seen in only a small per-
centage of fresh
craters
(Fig.
bution may be due to resolution
amounts of eolian
infilling.
2f).
This distri-
effects
and small
but
craters
to degraded would not influence
conclusions.
and
low 10 km (Fig. 2e). Lessthan 5 percentof the
Lunar
less than 1 km cannot be resolved.
resolution
20
Becauseof the large population,
craters
antly
bowl shaped.
The
as bowl shaped at
controlled
by the re-
Mariner
Between
No central peaks are observed in
mocks are associated
with
Eratosthenian-age
craters
The vast majority
fresh martian
craters
are
classification
of craters
small diameters is partly
the
is indicated
in Fig. 4b.
The percentage
craters
showing central
peaks steadily
Floor
'Variation
2c illustrates
terraces.
and
Their
km diameter.
these are not visible
percent
Morphologic
Fig.
20 percent of the fresh craters
have
and above 50 km all
fresh craters
feature.
Wall
terraces.
fresh
craters
but
the
diameter.
fresh craters less than 5 km in diameter, and an
extremely small percentage of .the total population between 5 and 10 km contain central peaks
central
PohnandOffield scale, basedon characteristics
Crater
km in
craters.
20
30 km, about
flat
floors,
contain
this
fresh
in B frames
fresh martian
than
Flat-floored
increases
exhibited
However,
or
20
percentage
of the fresh crater
population
which
has flat
floors,
as a function
of crater
size.
Less than 1 percent
of the fresh craters
below
20 km diameter are characterized
by flat-floors.
The occurrence of flat
floors
increases
markedly
(Fig. 2d).
on the charac-
exterior
than
fresh craters.
(1970) lunar scale is more difficult
teristics
less
Central peaks.
Less
than one percent of the population have the
blurred and broken rims characteristic
of Classes
II and III.
Detailed correlation with the Pohn
because of the lack of information
are
Comparison
with
the Moon and Mercury
our
2a shows the number of
A comparison
of the frequency
of occurrence
Cintala
et
al.:
Characteristics
of
I
+
•
z +++++++++
I0
0[++•+•1+•+
+ •
O.
0
i
IO
IOO
DIAMETER
20
I I I
40
60
ioo
80
DIAMETER
IOOO
+
80 CENTRAL
PEAKS
I-
,,,,
+
+
+
+ + +++++++ + + +
+++ ++++ + + +++++C.•
+ +, +,+
20
o
,+ +, +,•
40
60
DIAMETER
(KM)
,+
80
(KM)
IOO
40
so
80
I--%--+
•+
+
+
+
+
+
+
+
+
+
+
I
I
+
-
+1
+l
/+ + + + + + + + +q 40
•++++++
+++'
| + + + + + + + + + +/
' +++++++++'='
'
,--H+ ,+.+,.+,+,t.+,.+,+,•'•+J o
,00
I
j++++++++++++q
80
ß ,
o * ++++++++++'+
0
20
40
DIAMETER(KM)
Figure 2.
+
I+'+ • +'+'+ I'øø1' ' ' ' ' '
8
•--r•+ ++++++++++++1
2o
+
+
• +++++++++
++++
ß
•+ ++++++++++++++++d•
•'
'+ + + + + + + + + + • •o
o
+
+
+ + ++ ++
(KM)
øø1, , , , , , , •_+4I'ø
/
+++
+ + ++++•
+++ + + +++
• 40 +++++++++
+
ioo
• •o•
i i i i+''+
'1+'
•'+1'
+
+
I
I
119
I
+++++++++
o:•
,.,o
Craters
+++ + + +++
+ + +
I000
-
I
Martian
I00f++
+++•I I BOWL-SHAPED
FLATFLOOR +•l+
++++++++
+••
I0000
,., •
I
Fresh
60
80
..+,+•
•
,00 0
20
DIAMETER(KM)
•{orphologic characteristics
40
'
60
'
8o
+f.r"-_'/
IOO
DIAMETER(KM)
of the fresh martian crater population as a function of
diameter;
a) number of fresh bowl-shaped craters as a function of size; b-f) percentage of fresh
craters with a particular
feature as a function of crater size (e.g. - 98.5% of the fresh craters
between 10-20 km diameter are bowl-shaped).
b) bowl-shaped; c) flat-floored;
d) central peaks;
e) wall
terraces;
f)
floor
hummocks.
of terraces
and central
peaks as a function
diameter
for Mars, Mercury,
and the Moon is
shown in Fig. 4a, b.
The onset of terraces
occurs
at
about
and Mars.
craters
the
same
However,
with
terraces
consistently
diameter
on
the percentage
in
each
below values
M•on
(C. A. Wood, personal
class
central
peaks show a
higher diameters
than
ters.
Small amounts
may serve to obscure
many cases, while not
falls
both the M•on and
Mercury below 50 km. A small percentage of central peaks are seen at diameters of less than 10
km on Mars.
On the basis
of data
presented
by
Gault et al.,
(1975) and Smith and Sanchez (1973),
central peaks do not occur until 10-20 km diameter
on the Moon and Mercury (Fig. 4b). However, a
4O
•
CENTR.4L
PE.4KS
":50
-
• 2o
I
\
•
I
i
\
recent compilation
of lunar crater
data shows
that, within
a 13 million
square kilometer
area on
the nearside,
5 percent of the Class I craters
between 5 and 10 km diameter have central
peaks
of martian
size
for
the
of
\
\WALL
TERRACES
crater
communication).
Martian
slower rate of increase
at
do lunar and mercurian
craof eolian
infilling
on Mars
or bury the central
peaks in
changing the general fresh-
appearance.
Previous investigators
have attributed
the
differences
in central
peak and terrace
frequencies between the Moon and Mars (Hartmann,
1972; 1973) and the Moon and Mercury (Gault et al.,
1975) to dissimilar
surface gravitational
field
strengths.
The Moon and Mercury differ
in surface gravitational
accleration
by over a factor
of 2 (Moon, 0.16 relative
to Earth=l;
Mercury,
0.37).
The gravitational
acceleration
at the
surface of Mercury is approximately
the same
(about 5 percent less) as that of Mars (0.38).
Since Mars and Mercury have similar
surface
gravities,
features
such as terraces
which are
FLATFLOORSthought
to be gravity-controlled
(Gault et al.,
1975) should appear at similar
diameters if gravity is the dominant factor.
However, terraces
appear at smaller diameters on Mercury than on
•
• •o
Mars and the Moon (Fig.
o
I.O
IO.O
DIAMETER
I OO.O
( KM )
Figure 3.
Summaryof fresh crater
variations
with
crater
cate what percentage
feature
occurs
(e.g.
20% of all
in
diameter.
of craters
each
diameter
morphologic
Points
indi-
with specific
interval
bowl-shaped craters
tween 2 and 3 km diameter).
The area
each curve represents
total
population
feature.
Modified
from Mutch et al.,
4a).
The differences
between these planets strongly suggest that,
in
addition
to gravitational
effects,
other factors
such as varying impact velocities
and dissimilar
substrate
characteristics
may also be important.
Compilation
of a complete data base for the Moon
and Mercury will
allow more detailed
comparisons
to
be
made.
occur beunder
of each
1976.
Acknowledgements. This work was performed
under NASA grants NGR-40-002-008 and NGR-40-002116 which are gratefully
acknowledged.
Thanks
120
Cintala
--
40
bJ
-
•• •
-
•
2o
-
••
•••
++
::::::::::::::::::::::::::::::::::::
I
ßr.•r.•'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.•
J. Geophys. Res., 80, 2444-2460, 1975.
i:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:..•
Interplanet Variations in Scale
I•
,4'
of
Crater
Morphology--Earth,
Mars, Moon,
i .'•'•X'.';':':':':.:.:':':':.:.:':':':':':':':':':':':':':':':':':':'
Hartmann, W. K.,
••i':':':':':':':':':':':':':':':':':':':':,:':':':':':':':':•
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Icarus,
80
Initial
_
'
I•
+
I•
•
-
'[':':':':':'•
':.:.:.:.:.:•
......
C':':':':':':':':':.:.:.•
-
•:.:':':.:.:.:.:.:.:.:.:.:.:.:.:.:.:.
.•..•..•:.:.:.:-:.:.:.:.:.:.:.:.:.:.:.:.:.:.:
.•
.• .....
.............................:.:...:...:.:.:.:.:.:.:.:.:.:.
eeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
eeeeeeeeeeeee
.eeeß ß ß ß ß
(........... /................:..............'.....:.:.:.:.:.:.:.:..'.:.
:.x
mitted to Lunar Science
Institute,
Houston, TX,
Howard, K. A., Fresh Lunar
view of Variations with
DIAMETER
(KM)
Comparison of Mars data with the Moon
of crater diameter (Mercurydata from Gault et al.,
1975; l-nar data from Smith and Sanchez,1973,
as modified by Gault et al., 1975).
In Gault et
al. lunar wall terrace data below 10 km is inplotted
but is corrected
here.
Mar-
tian central peak data below 10 km are enhanced
are extended to Ray Arvidson
and Ken Jones for
the compilation of the Mars data bank, to R.
Stockman, R. D'Alli,
S. Grenander, and C. A. Wood
for discussion and to J. Ralske for help in
of the manuscript,
and K. A. Howard for
the manuscript.
their
and to D. E. Gault
critical
reviews
of
L. A. Soderblom,R. P. Sharp, and
J. A. Cutts, The Surface of Mars I,
Cratered
Terrains, J__.Geophys.Res., 76, 313-330, 1971.
Mutch, T. A., R. A. Arvidson, K. L. Jones,
J. W. Head, andR. S. Saunders,Geologyof Mars,
Princeton Press, in press, 1976.
Pike, R. J., Depth/Diameter Relations of Fresh
Lunar Planetary Lab., p. 71, The University of
Tucson, AZ, 1963.
Arvidson, R. A., T. A. Mutchand K. L. Jones,
and Associated
Aeolian
Features
on
Mariner 9 Photographs: An Automated Data
Gathering and Handling System and SomePre-
liminary Results, .Moon,9, 105-114, 1974.
Arvidson, R. A., Morphologic Classification
of
Martian Craters and SomeImplications,
Icaru_s, 22,
Geophys.Res. Lett.,
1, 291-294, 1974.
Pike, R. J., GeneticImplications of the Shapes
of MartianandLunarCraters, Icarus, 15,
384-395,
1971.
Pohn, H. A. and T. W. Off,eld, Lunar Crater
Morphology and Relative-Age Determination of
Lunar GeologicUnits--Part 1. Classification,
Craters:
C. A. Wood, and C. R. Chapman, Comm.of the
264-271,
1974.
Cintala, M. J., J. W. Head, and T. A. Mutch,
Depth/DiameterRelationships for Martian
and Lunar Craters, EOS,56, 389, 1975.
Cintala, M. J., J. W. Head, and T. A. Mutch,
Depth/Diameter Relationships for Craters
Morphology as a Function of Dia-
meter, A Possible Criterion for Crater Origin,
Mod. Geol., _4, 51-59, 1973.
Soderblom,
L. A., T. Kreidler, andH. Masursky,
Latitudinal
Distribution
of a Debris Mantle
on the Martian Surface,J. Geophys.
Res., 78,
4117-4122,
Wetherill,
1973.
G. W., Late Heavy Bombardment
of the
Moon and Terrestrial
Planets:
Proc. 6th
Lunar Sci. Conf., Geochim.Cosmochim.
Acta,
Suppl. 6• 2, 1539-1561, 1975.
Wilhelms,D. W. and J. F. McCauley,Geologic
Mapof the Near Side of the Moon,Geologic
Atlas of the Moon, 1971.
Wood,C. A., The Systemof LugtarCraters, Revised,
Moon, 3,
408-411,
1972.
on Mars, the Moon, and Mercury, submitted to
Lunar Science VII,
Houston,
-
Geol Surv. Res., 153-162, 1970.
Arthur, D. W. G., A. P. Agnieray, R. A. Horvath•
Craters
J. Geophys. Res., 79, 3917-3931, 1974.
Murray, B.C.,
Smith, E. I. and A. G. Sanchez, Fresh Lunar
References
Arizona,
Obliteration Intermediate in Martian History,
Lunar Craters: Revision from Spacecraft Data,
for visibility.
preparation
1974.
Jones, K. L., Evidence for an Episode of Crater
and Mercury for the frequency of occurrence of
terraces (a) and central peaks (b) as a function
correctly
VII, Lunar Science
1976.
Impact Craters: ReSize, Proc. 5th Lunar
Sci. Conf., Geochim.Cosmochim.
Acta, 1, 61-
69,
._.... :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
o
20
40
60
80
Figure 4.
•
of Substrate
Characteristics in DeterminingMorphology
and Morphometry
of Fresh Lunar Craters, sub-
-
r:':.:.'.'.'.,
) ß ß e'ee.ee
.•
•
+
Moon , 12, 299-329, 1974.
Head, J. W., The Significance
"+-"•-I"'
'1-ßßßße[•eeeeeeeeeeeeeeeeeeeeeeeeoe,,,
ßßßßß,, ßßßßeee
e,
-
Analysis of Cratering Chronology,
Head, J. W., Processesof Lunar Crater Degrada'tion: Changesin Style with GeologicTime,
MARS
•
+
_
-
/•
+
+
+
• 20
Ill
,•x•x•
+
-
40
1972.
J. Geophys. Res., 78, 4096-4116, 1973.
+ + + + MOON
-
17, 707-713,
====================================================
Hartmann, W. K., Martian Cratering, 4, Mariner 9
- MERCURY
_
Z
Craters
,..:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:
•
-
o
(.3
of Fresh Martian
Cintala, M. J. andJ. W. Head,The Relationshipof
++
- •
n-
Characteristics
MERCURY
Morphology and Morphometryin Fresh Lunar
Craters, submitted to Moon, 1976.
•MOON.,..•MARS. *********************%**************
+
.......',............................
Gault,
D. E., J. E. Guest, J. B. Murray, D.
I':':':':':':':':':':':':':,:':':':':':':':':':':*
.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:•
Dzurisin, and M. C. Malin, SomeComparisons
•
I!
::::::::::::::::::::::::::::::::::::::::::::::::::
of Impact Craters of Mercuryand the Moon,
•
• .... W.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.•
8O
z
et al.:
TX,
1976.
Lunar Science Institute,
(Received February 5, 1976;
accepted
February
17,
1976.)