Photogeologic mapping of Mariner photographs characterizes major stratigraphic units of the Martian equatorial region. The low resolution photomosaic ship across Meridiani Sinus Deucalionus Regio is divided into regional map units based on albedo and crater density. High resolution frames reveal map units defined by varying surface texture, crater densities, and degree of crater sharpness. Mariner photographs provide clear evidence of eolian action and channelization by fluid flow

Dehon, R. A.

English

NASA Technical Reports Server

NGR 19-013-002
FINAL TECHNICAL REPORT
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k PHOTOGEOLOGIC MAPPING OF MERIDIANI
SINUS REGION FROM MARINER 6 AND 7 IMAGERY
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https://ntrs.nasa.gov/search.jsp?R=19740007377 2020-03-23T13:15:50+00:00Z
Photdgeologic Mapping of the Meridiani Sinus
Region from Mariner 6 and 7 Imagery
ABSTRACT
Photogeologic mapping of Mariner photographs characterizes
major stratigraphic units of the Martian equatorial region.
The low resolution photomosaic ship across Meridiani Sinus-
Deucalionus Regio is divided into regional map units based
on albedo and crater density. High resolution frames re-
veal map units defined by varying surface texture, crater
densities, and degree of crater sharpness. Mariner photo-
graphs provide clear evidence of eolian action and channel-
ization by fluid flow.
INTRODUCTION
This report contains the results of geologic mapping of
Martian surface within the limits imposed by Mariner 6 and
7 imagery. The same techniques used in mapping the lunar
surface are applied to the interpretation of Mariner
photographs (Hackman, 1960; Carr, 1970; and Wilhelms and
McCauley, 1971). For the purpose of this study, test areas
were limited to the equatorial region of the planet. The
primary objectives are:
1. To distinquish surface patterns of material
distribution
2. To establish a local framework of time sequences
in depositional history
DeHon p. 2
3. To recognize processes operating on the surface.
The study was performed using unrectified JPL/IPL versions
of the imagery and a composited shaded map of the Meridiana
Sinus region by Cross (1971).
Geologic mapping was carried out at three scales within
the Meridiani Sinus region. Three high resolution frames
(6N18, 6N20, and 6N22) were selected for their clarity of
detail and near vertical nature. One frame of low re-
solution (6N21) was selected as an intermediate between
mapping on high resolution photographs and regional mapping.
The albedo map of Meridiani Sinus (Cross, 1971) was choosen
as the best available regional base combining albedo
variations of the far encounter phase with surface detail
of the near encounter mission.
LARGE SCALE MAPPING
The results of mapping on high resolution photographs
is shown in figures 1, 2, 3, and 4. In general, the
surface is divisible into recognizable mapping units
displaying a diversity of surface textures, albedo
variations, and overlapping or transecting relationships.
Due to resolutions lower than those available for lunar
mapping, contacts are observed as gradational boundaries
and age relationships are, in part, obscure.
Craters are grouped into four morphological classes
c:2---
DeHon p. 3
based on degree of rim crest sharpness and apparent
relative depth in the manner of Pohn and Offield .(1970)
for lunar craters. Superposition of crater materials
indicates that the morphological classification is, in
part, age related also. Subdivision of crater materials
is also possible. The only significant difference from
lunar craters was the occurrence of a more extensively
developed interior apron at the base of the crater walls
(fig. 3). This material is probably talus or colluvium
worn from the crater walls by more active surface processes
of degredation.
In general, regional units of plains and featureless
plains-forming materials appear to be the youngest
deposits occurring in topographic lows. The occurrence
of sinuous ridges similar to lunar "wrinkle ridges" and
low lobate scarps (fig. 2) in some plains material suggests
emplacement by flow similar to lunar mare materials. Other
plains may be either eolian or volcanic in origin. Lineate
plateau material is bracketed in a stratigraphic sense
by its superposition on cI craters and it is in turn
overlain by c3 crater materials. Relative ages of hummocky
and subdued hummocky materials are less distinquishable
and uncertain. Embayment by featureless plains and lineate
plateau materials in figure 3 indicates that hummocky
and subdued hummocky materials are older. The relation-
ships on other photographs are ambiguous.
>7 -
DeHon p. 4
SMALL SCALE MAPPING
Small scale mapping of frame 6N21 is shown in figures
5 and 6. Mariner 6N22 is included in the central- right
hand portion of this frame.
A major feature of this map is the contact between
textured plateau material and plains materials. The units
are texturally distinct as well as differing in albedo.
The albedo boundary corresponds to the Sabaeus Sinus--
Deucalionis Regio boundary. However, crater frequency
counts of the two units do not reveal any marked differ-
ence. The plain.s materials might be similar to the
textured plateau material with a thin overlay of
surfacing deposits which is sufficient to brighten the
area and mantle low surface irregularities without
greatly affecting larger surface irregularities. Also
prominent in this region are faint sinuous channels which
in overall appearance are similar to gullied terrain in
arid regions.
REGIONAL MAPPING
Figures 7 and 8 are based on Cross's durface map
(1971). Surface resolution varies greatly across the
map area, hense, the amount of detail mapped varies
accordingly. Sources for mapping information include
individual low resolution frames and photomosaics of
frames in the region (6N9-25, 7N1-9)
-4--
DeHon p. 5
Regional map units at this scale are albedo; therefore,
they are biased by the overall albedo pattern of the
region. Such bias may show little more than transitional
surface mantle materials rather than bedrock differences.
Rugged material, dark cratered terrain, and light colored
terrain have similar crater frequencies and may reflect the
extent of deposition or nondeposition of eolian materials.
Dark smooth terrain materials, however, exhibit low crater
densities and are probably younger basin filling materials
of volcanic origin.
The albedo pattern of dark material of Margaritifer
Sinus -- Oxia Palus forms an incomplete half circle
suggestive of a large filled basin. Radar elevations across
Margaritifer Sinus and Deucalionis Regio exhibit a scarp
that coincides with the light-dark boundary facing east-
ward toward light materials of Deucalionis Regio. East
of the scarp the elevations rise to the point that the
interior is as high as the rim. One possible interpre-
tation of the pattern is that the area represents a large
mare-like basin modified by later infilling and construct-
ional deposition in the interior. To the southeast and
east, the basin is filled to the point of obliteration.
Materials mapped as surficial materials occur as bright
patches on crater rims, crater floors, and dune field-
like deposits. These materials are probably eolian in
DeHon p. 6
origin , and seem to indicate a dominant wind from the north.
Of special significance are the broad sinuous areas
mapped as valley and canyon materials. Photographic cover-
age of this area is several orders of magnitude too low to
delineate precisely the distribution and gradient of these
features. However, their presence reveals a significant
addition to the possible surface processes operating on
the planet. The Sinuous and branching patterns seen at
this scale are suggestive of fluid water erosion.
CONCLUSIONS
Mariner 6 and 7 resolutions provide distinct limita-
tions on mapping; however, this exercise does confirm that
geologic mapping is possible. This brief study indicates
that diverse processes are operating on the surface of
mars.
In terms of planet history, the mapping reveals an
older period of crater formation similar to the early
history of the lunar surface. Unlike the moon, however,
martian surface modifing processes have continued to
operate. These processes include: volcanism, eolian
processes, and possibly the action of permafrost and
liquid water.
RETROSPECT
Mariner 9 photography has greatly improved resolution
of surface features. Units defined on the high resolution
DeHon p. 7
Mariner 6 and 7 images are generally transferable to later
coverage. Regional patterns are not recognized in the
later coverage and probably reflect the distribution of
thin surface mantles. Physiographic maps of Mars do not
show evidence of the supposed basinal character of the
region mapped in figure 7. The valley and canyon units of
the western portion of the regional map do coincide with
the location of the eastern terminus of the canyon
system and were the first indications of this prominent
feature.
DeHon p. 8
REFERENCES
Carr, M. H., editor, 1970, A strategy for the geologic
exploration of the planets: U. S. Geol. Survey
Cir. 640, 105p.
Cross, C. A., 1971, Mars chart; Meridiana Sinus and
environs: Rand Corp., R-757-NASA.
Pohn, H. A., and Offield, T. W., 1970, Lunar crater
morphology and relative age determination of lunar
geologic units--pt. 1: Classification, in Geological
Survey Research 1970: U. S. Geol. Survey Prof.
Paper 700-C, p. 153-162.
Wilhelms, D. E. and McCauley, J. F., 1971, Geologic
Map of the near side of the moon: U. S. Geol.
Survey Misc. Geol. Inv. Map 1-703.
DeHon
ILLUSTRATIONS
Figure 1. Geologic map of frame 6N18
Figure 2. Geologic map of frame 6N20
Figure 3. Geologic map of frame 6N22
Figure 4. Explanation for figures 1, 2, and 3
Figure 5. Geologic map of frame 6N21
Figure 6. Explanation for figure 5
Figure 7. Generalized geologic map of Meridiani
Sinus region. Only major surface units
are shown.
Figure 8. Geologic map of Meridiani Sinus
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CRATER UNITS REGIONAL UNITS
Smooth slope material
Sharp-rimmed crater
material
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C Ct CW Plains material Featureless plains
C Cf Moderately sharp- material
cr rimmed crater
material
Crater material
C, crater material undivided Lineate plateau
Ca, apron material material
Ct, wall terrace material
Cw, wall material
Cr, rim material h hs
Cf, floor material
Hummocky material Subdued hummocky
Subdued crater material
material
Highly subdued
crater material
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EXPLANATION
CRATER UNITS REGIONAL UNITS
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Sharp-rimmed crater material
Plains material Smooth plateau material
C3
Moderately sharp-rimmed
crater material I I p [
C Lineate plateau Hilly plateau Textured plateau Rolling plains
2  material material material material
Subdued crater
material
Cl
Highly subdued crater
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Contact Lineament Trough Buried crater
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Photogeologic mapping of Meridiani Sinus region from Mariner 6 and 7 imagery

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