Earth and Planetary Science Letters 294 (2010) 306–320
Contents lists available at ScienceDirect
Earth and Planetary Science Letters
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / e p s l
Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for
the recognition of debris-covered glacier and valley glacier landsystem deposits
James W. Head a,⁎, David R. Marchant b, James L. Dickson a, Ailish M. Kress a, David M. Baker a
a
b
Department of Geological Sciences., Brown University, Providence, RI 02912 USA
Department of Earth Sciences, Boston University, Boston, MA 02215 USA
a r t i c l e
i n f o
Article history:
Accepted 26 June 2009
Available online 30 July 2009
Keywords:
Mars
lobate debris aprons
lineated valley fill
debris-covered glaciers
glaciation
rock glaciers
a b s t r a c t
Lobate debris aprons (LDA) and lineated valley fill (LVF) have been known to characterize the mid-latitude
regions of Mars since documented by Viking; their flow-like character suggested that deposition of ice in
talus pile pore space caused lubrication and flow during an earlier climatic regime. A number of factors have
remained uncertain, however, including the detailed structure and texture of LDA/LVF, the relationships
between them, their direction of flow, the origin and abundance of the lubricating agent, and their exact
mode of origin (e.g., ice-assisted rock creep, ice-rich landslides, rock glaciers, debris-covered glaciers). We
use new High-Resolution Stereo Camera (HRSC) image and topography data, in conjunction with a range of
other post-Viking data sets, and new insights provided by cold-based terrestrial glacial analogs, to assess the
characteristics of LDA/LVF in the northern mid-latitudes of Mars. We find evidence that the characteristics
and flow patterns of the LDA and LVF are most consistent with Late Amazonian debris-covered glacial valley
landsystems. The broad distribution and integrated characteristics of the LDA/LVF systems suggest that
earlier in the Amazonian, climatic conditions were such that significant snow and ice accumulated on midlatitude plateaus and in valleys, producing integrated glacial landsystems, the remnants of which are
preserved today beneath residual sublimation till derived from adjacent valley walls. Atmospheric general
circulation models suggest that these climatic conditions occurred when Mars was at a spin-axis obliquity
of ~ 35°, and the atmosphere was relatively dusty. Glacial flow modeling under these conditions produces
patterns similar to those documented in the LDA/LVF, and SHARAD radar data suggests that significant
amounts of ice remain sequestered below the sublimation lag today.
© 2009 Elsevier B.V. All rights reserved.
1. Introduction
Mars is currently a cold, hyper-arid global desert (Baker, 2001);
water is currently sequestered in the regolith-cryosphere, with the
major surface reservoir residing in the extensive polar caps, and very
small amounts in the atmosphere (Carr, 1996). Evidence is growing
that in its past history, Mars has been characterized by significant
variations in its spin-axis/orbital elements (obliquity, eccentricity and
precession) (Laskar et al., 2004) and that these variations have led to
the redistribution of water in the polar ice deposits to lower latitudes
to create ice ages and their related deposits (e.g., Head et al., 2003).
This has led to a renewed interest in the development of criteria to
recognize non-polar ice-related, glacial and periglacial deposits that
might represent the record of these excursions. Topographic and
imaging data acquired by recent spacecraft have revolutionized our
understanding of these deposits, providing detailed information that
helps to characterize their key parameters (structure, morphology,
slopes, elevations, morphometry, stratigraphic relationships, etc.) that
⁎ Corresponding author.
E-mail addresses: james_head@brown.edu (J.W. Head), marchant@bu.edu
(D.R. Marchant).
0012-821X/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.epsl.2009.06.041
are essential to interpreting these deposits. In particular, the HighResolution Stereo Camera (HRSC) on board the Mars Express Spacecraft has provided image data and high-resolution digital elevation
models (Neukum et al., 2004a,b; Gwinner et al., 2005; Scholten et al.,
2005) that, together with complementary data from HiRISE, CTX,
THEMIS and MOLA, have permitted the assessment of these types of
features in the northern mid-latitudes of Mars.
Fretted terrain and fretted channels are very well developed in the
northern part of Arabia Terra (Sharp, 1973) and were clearly identified
in Viking data as the site of development of lobate debris aprons (LDA)
(Fig. 1B) and lineated valley fill (LVF) (Fig. 1C) (Squyres, 1978, 1979).
The detailed geological history and chronology of this region (McGill,
2000) provide a framework for the interpretation of modification
processes operating on and near the dichotomy boundary. McGill
(2000) underlines the conclusion that fretted channels and valleys
formed early in Mars history (prior to middle Hesperian) and that the
associated LDA and LVF represent Amazonian-aged modification of
the fretted topography. Carr and Schaber (1977) analyzed the early
Viking Orbiter images and concluded that frost creep and gelifluction
were the primary processes in LDA formation. Squyres (1978)
documented the fact that in the fretted terrain, debris aprons (LDA),
characterized by sharply-defined flow fronts and convex-upward
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
307
Fig. 1. A. Locations of areas discussed in this study showing lobate debris aprons (LDA) and lineated valley fill (LVF) and evidence of glaciation. Red lines show 30°–50° N latitude band
in which they occur. Numbers refer to specific localities discussed in the text. B. Viking image of typical lobate debris aprons (Squyres, 1978, 1979) (46° N, 311° W; Viking Orbiter frame
338S31). C. Viking image of typical lineated valley fill (Squyres, 1978, 1979) (32° N, 341° W; Viking Orbiter frame 205S18).
surfaces, extend from massifs and escarpments outward to distance
up to ~20 km. Squyres (1978, 1979) interpreted the aprons to have
resulted from mass-wasted debris caused to flow by interstitial ice; he
envisioned that during periods of climate change, atmospheric water
vapor would diffuse into talus piles formed at the base of steep
topography, and the resulting interstitial ice would cause mobilization
and flow of the talus to produce lobes around isolated massifs.
Longitudinal striae (ridges and grooves in surface debris) seen on the
floors of the fretted valleys (LVF) were interpreted to be formed by iceassisted debris aprons flowing from valley wall talus slopes and
converging in the middle of the valley floor (Squyres, 1978, 1979). In
the late 1970s a number of workers noted that some LVF in the
Nilosyrtis region appeared consistent with down-valley flow (as
reviewed by Baker (1982), p. 96–98). Following earlier ideas by Kochel
and Baker (1981), Kochel and Peake (1984) provided detailed
descriptions of geomorphological relationships and interpreted
some debris aprons as formed by processes similar to those of
terrestrial ice-cored or ice-cemented rock glaciers. Kochel and Peake
(1984) further noted a transition from flow-parallel to flow-transverse
ridge-and-furrow topography. Lucchitta (1984) interpreted the LDA
and LVF as flow of debris with interstitial ice and showed evidence of
local down-valley flow of LVF, likening some examples to flow
patterns in glacial ice in Antarctica. Carr (1996; p. 116–120) urged
caution in the general interpretation of a range of landforms as being
due to glaciation (see Kargel and Strom, 1992; Kargel, 2004), on the
basis of 1) the fact that the glacial hypotheses requires major climate
change late in Mars history (e.g., Baker et al., 1991) for which he found
little supporting evidence, and 2) that the low erosion rates in the
Amazonian argues against any major climate excursions accompanied
by precipitation, as envisioned by Baker (2001).
Pierce and Crown (2003) used new image and altimetry data to
examine LDA in the Hellas region and found evidence for a wide range
of possible ice content, interpreting the evidence to be consistent with
multiple models of apron formation (e.g., rock glacier ice-assisted
creep of talus, ice-rich landslides, debris-covered glaciers), with
typical LDA resulting from flow of debris that was enriched in ground
ice. Mangold (2003) presented evidence that ice content in LDA may
exceed pore space, and Li et al. (2005) measured LDA MOLA profiles
and compared these to simple plastic and viscous power law models
for ice-rock mixtures; they concluded that LDA were ice-rich rock
mixtures with some perhaps N40% ice by volume. Chuang and Crown
(2005) documented the detailed character of sixty-five LDA in the
Tempe Terra/Mareotis Fossae region and concluded that they
consisted of mixtures of debris and ice, but that it was “difficult to
constrain the internal distribution of ice or the method of debris apron
initiation from the current datasets.” In summary, all workers agree
308
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
that the formation of LDA and LVF involves both talus and ice, but
there is disagreement as to the amount of ice: One end-member calls
on formation by ice-assisted creep of talus (often defined as producing
a “rock glacier”) (e.g., Squyres, 1978, 1979), while another endmember calls on formation as debris-covered glaciers, (predominantly glacial ice with a cover of sublimation lag or till) (e.g., Head
et al., 2006a,b). Here we develop criteria to distinguish between these
end-members and investigate a wide range of occurrences to assess
the origin of LDA and LVF.
Although temperate glacial and periglacial climates and analogs can
offer insight into these environments, the extremely cold and hyper-arid
conditions on Mars are more likely to be related to environments in
which cold-based glaciation is the dominant process and temperatures
are virtually always below the freezing point of water (e.g., Marchant and
Head, 2007). Terrestrial cold-based glacial analogs have recently been
applied to the analysis of fan-shaped deposits on the NW flanks of the
Tharsis Montes and Olympus Mons, and have been interpreted
to represent extensive tropical mountain glaciers formed by enhanced
snow and ice deposition during periods of high obliquity in the
Amazonian (Williams, 1978; Lucchitta, 1978; Head and Marchant,
2003; Neukum et al., 2004a,b; Shean et al., 2005, 2007; Head et al.,
2005; Milkovich et al., 2006; Forget et al., 2006; Kadish et al., 2008).
Additional Earth glacial analogs have been used to develop criteria
for the recognition of glacial deposits in various topographic and
environmental settings on Mars (Marchant and Head, 2006). These
criteria have recently been applied to the assessment of the fretted
terrain, one of the hallmark morphologies of the highland–lowland
boundary region in the northern mid-latitude Deuteronilus–Protonilus
Mensae area (30°–50° N and 10°–75° E) (Fig. 1). An increasing
awareness of the possible role of glacial deposits on Mars (e.g., Lucchitta,
1981, 1984; Head and Marchant, 2003; Marchant and Head, 2007) led to
investigation of the question of whether the accumulation of snow and
ice, and resulting glacial activity, could account for some of the observed
characteristics of the LDA and LVF in the fretted terrain. In one area
analyzed (Fig.1, point 1) (~37.5° N, 24.2° E) (Head et al., 2006a) evidence
was presented that lineated valley fill formed in multiple accumulation
zones in breached craters, alcoves, and tributary valleys and flowed
laterally down-valley forming a major trunk system that was characterized by compression of ridges at constrictions, tight folds at converging
branches, and a lobate, convex-upward terminus. In a second area (Fig.1,
point 2) (~40.5° N, 34,5° E) (Head et al., 2006b), a single integrated
glacial flow system was documented covering ~30,000 km2 and
consisting of multiple, theater-headed, alcove-like accumulation areas,
converging patterns of downslope flow into several major valley
systems, and broad piedmont-like lobes where the LVF extended out
into the adjacent lowlands. The features and deposits in these two areas
were interpreted to represent intermontaine valley glacial systems
dating from earlier in the Amazonian.
An additional detailed morphological analysis of a 70,000 km2 region
just east of the area treated by Head et al. (2006b) (north-central
Deuteronilus Mensae, south of Lyot, in the vicinity of Sinton Crater; Fig.1,
point 5) was described by Morgan et al. (2009), and is characterized by
the distinctive sinuous ~2 km-high plateau scarp boundary, outlying
massifs to the north, and extensive fretted valleys dissecting the plateau
to the south. These features are modified by processes that form LVF in
the fretted valleys, and LDA along the dichotomy scarp and surrounding
the outlying massifs. High-resolution HRSC image and topography data
show that LVF and LDA deposits are comprised of the same material,
show integrated flow patterns, and originate as debris-covered valley
glaciers; the proportion of ice and debris involved is high and a
significant amount of ice (hundreds of meters) is likely to remain today
beneath a thin cover of sublimation till. There is depositional evidence to
suggest glacial highstands at least 800 m above the present level,
implying previous conditions in which the distribution of ice was much
more widespread. In Nilosyrtis Mensae, farther east along the dichotomy
boundary (Fig. 1, points 9, 10), LVF and LDA show stratigraphic,
topographic, and textural relationships that indicate extensive glaciation
along the boundary and multiple phases of glacial overprinting during
the late Amazonian (Levy et al., 2007). Evidence was analyzed and
presented for the regional integration and flow of LVF material and its
interpretation in the context of cold-based glaciation in the Antarctic
Dry Valleys.
The synthesis of these areas led to several additional questions:
1) What was the original thickness of the glacier ice? 2) How much
ice-surface lowering, through sublimation, retreat and ice loss, has
occurred to bring the LDA and LVF surfaces to their presently observed
levels? 3) Have there been multiple periods of glaciation, and if so,
over what time periods? Preliminary analyses (e.g. Marchant and
Head, 2008) suggested that the LDA and LVF might be parts of a larger
phase of glaciation, during which glacial ice was much thicker and
perhaps completely filled the valleys. Dickson et al. (2008) described
evidence for glacial thickness maxima and multiple glacial phases in
the Coloe Fossae region of the dichotomy boundary (Fig. 1, point 7).
They documented the topography associated with a sloping lobe
interpreted to be evidence of a glacial highstand that was part of a LVF
glacial landsystem. The elevation difference between the upper limit
and the current surface of the LVF at the study site is ~ 920 m and
Dickson et al. (2008) interpreted this difference to reflect the
minimum amount of ice-surface lowering of the valley glacier system
during downwasting and retreat. Consistent with a general lowering
of the ice surface are multiple moraines and/or trimlines, and changes
in LVF flow patterns, including local flow reversals, as the ice retreated
and decreased in thickness. Furthermore, the clear superposition of
several lobes out onto the current surface of the LVF indicates that a
smaller-scale phase of glaciation followed the lowering of the valley
glacial landsystem. These data suggest that the major Late Amazonian
glaciation that produced LVF in this region involved significantly
larger amounts of glacier ice than previously thought, and that
subsequent, less extensive glaciation followed (Dickson et al., 2008).
2. Synthesis of criteria for recognition
On the basis of these studies and using a range of terrestrial
analogs most likely to apply to the recent cold-desert environment of
Mars (e.g., Marchant and Head, 2006, 2007), the following criteria
have been developed to assist in the identification of debris-covered
glacial-related terrains on Mars. We first list the features (Fig. 2),
followed by the interpretation of each, listed in parentheses: 1)
alcoves, theater-shaped indentations in valley and massif walls (local
snow and ice accumulation zones and sources of rock debris cover)
(Fig. 2A), 2) parallel arcuate ridges facing outward from these alcoves
and extending downslope as lobe-like features (flow-deformed ridges
of debris) (Fig. 2B), 3) shallow depressions between these ridges and
the alcove walls (zones originally rich in snow and ice, which
subsequently sublimated, leaving a depression) (Fig. 2B, C), 4)
progressive tightening and folding of parallel arcuate ridges where
abutting adjacent lobes or topographic obstacles (constrained debriscovered glacial flow) (Fig. 2B, C), 5) progressive opening and
broadening of arcuate ridges where there are no topographic obstacles
(unobstructed flow of debris-covered ice) (Fig. 2B, C), 6) circular to
elongate pits in lobes (differential sublimation of surface and nearsurface ice) (Fig. 2B, C), 7) larger tributary valleys containing LVF
formed from convergence of flow from individual alcoves (merging of
individual lobes into LVF) (Fig. 2A), 8) individual LVF tributary valleys
converging into larger LVF trunk valleys (local valley debris-covered
glaciers merging into larger intermontaine glacial systems) (Fig. 2A),
9) sequential deformation of broad lobes into tighter folds, chevron
folds, and finally into lineated valley fill (progressive glacial flow and
deformation) (Fig. 2B, C), 10) complex folds in LVF where tributaries
join trunk systems (differential flow velocities causing folding)
(Fig. 2B, C), 11) horseshoe-like flow lineations draped around massifs
in valleys and that open in a downslope direction (differential glacial
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
309
Fig. 2. A. Synoptic High-Resolution Stereo Camera (HRSC) image data superposed on HRSC DTM, with HRSC stereo-derived, color-coded topography and topographic contours
displayed. This product is typical of those used in this study and is essential in showing the detailed relationships between topographic and morphologic features, particularly for
determining E–W-oriented slope measurements where MOLA groundtracks are widely spaced. Northern Arabia Terra region (24° E, 39° N; Fig. 1, point 1). Numbers here, and in B and
C show the types of features described in the text as criteria for recognition of glacial deposits. Inset box shows location of B. Contour interval is 250 m. Portion of HRSC images
1483_0000. B. Degraded impact crater and LDA and LVF. Accumulation of LDA along the crater walls has led to flow toward the breach in the crater rim, and out into the surrounding
valley, where the flow joins LVF from the alcove to the east, resulting in complex patterns of folding and deformation. Location is shown by box in A. Portion of HRSC image
1201_0000. C. LDA at the edge of the dichotomy boundary converging northward downslope to form LVF; note that the LDA appear to emerge from the top of the plateau, suggesting
the present of a plateau icefield feeding the valley glacial landsystem. The lobes are seen to transition form arcuate, outward-facing shapes, to chevron shaped, and then to compress
further and merge into LVF. THEMIS V09872024 draped on MOLA; VE = 5×. Scene is ~ 16 km across at the crest of the slope face.
flow around obstacles) (Fig. 2A), 12) broadly undulating along-valley
topography, including local valley floor highs where LVF flow is
oriented in different down-valley directions (local flow divides where
flow is directed away from individual centers of accumulation)
(Fig. 2A), 13) integrated LVF flow systems extending for tens to
hundreds of kilometers (intermontaine glacial systems) (Fig. 2A), and
14) rounded valley wall corners where flow converges downstream,
and narrow arete-like plateau remnants between LVF valleys (both
interpreted to be due to valley glacial streamlining) (Fig. 2A).
Taken together, the occurrence of these types of features is
interpreted to represent the former presence of debris-covered
glaciers and valley glacial systems in the Deuteronilus–Protonilus
region (e.g., Head et al., 2006a,b). Snow and ice accumulating in
alcoves, together with rock debris shed from adjacent steep walls,
created debris-covered glaciers that flowed downslope, merging with
other ice lobes to form ever-larger LVF glacial systems. Using these
criteria, we now explore other parts of the mid-latitudes (Fig. 1) to
assess evidence for similar features and processes.
3. Application of the criteria to other parts of the Deuteronilus–
Protonilus region
Squyres (1978) showed that locations of LDA and LVF were
concentrated in a distinct mid-latitude band, suggesting a climate
control on their origin. We have applied the criteria for glacial deposits
outlined above to detailed analyses of several additional areas in this
northern mid-latitude region (Fig. 1), and we report a summary of our
findings here. Although evidence has been presented for a debriscovered glacier origin for some occurrences of the LDA and LVF, a
number of factors have remained uncertain, including: 1) determining
the direction of flow in LDA and LVF, either normal to the valley
(Squyres, 1978), or possibly parallel (down-valley) (Lucchitta 1984);
2) understanding of the detailed structure and texture of the LDA;
3) understanding of the relationships between the LDA and the LVF;
4) establishing the relationship of LDA and LVF to adjacent walls;
5) providing evidence for the origin of the lubricating agent and flow
mechanism; 6) distinguishing the mode or modes of origin of the LDA
310
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
and LVF (e.g., ice-assisted rock creep, ice-rich landslides, rock glaciers,
debris-covered glaciers); and 7) assessing the implications for the
geological history of Mars. We address these questions in an analysis
of several regions in the northern mid-latitudes.
3.1. North-Central Arabia Terra (Fig. 1, location 3; Fig. 3)
Regional analyses of LVF in the southern part of this area (Head
et al., 2006a) have shown evidence for local sources of LVF in alcoves
in valley walls, down-valley flow, merging of flowlines into broad
trunk valleys, extensive along-valley flow, and termination in lobate
deposits, all features that are similar to valley glacial landsystems
on Earth (Boulton and Eyles, 1979; Eyles, 1983; Benn et al., 2003). In
this preliminary analysis we mapped a ~50,000 km2 area (Fig. 3) just
north of the area of LVF interpreted to be a valley glacial landsystem
(Head et al., 2006a). We found it useful to subdivide LDA into linear
(occurring along valley walls and crater interiors) and circumferential
(aprons generally surrounding isolated massifs) (Fig. 3A).
Fig. 3. Northern Arabia Terra (Fig. 1): A. Topographic contour map of study region: 100 m contour interval. Arrows show mapped directions of flow. Boxes show locations of Figs. B–F.
B. Massif with circumferential LDA. Themis V13879005 with Viking inset for comparison. C. Linear LDA along crater wall. Note alcoves, lobes, and divergence around obstacle. Themis
V10834007. D. Large fold where LVF converges and becomes LDA. Themis V11433004. E. Massif LDA meet and flow laterally from a divide, forming LVF. Themis V14216012. F. Linear
LDA blocked by parallel ridges, merges to form LVF and piedmont lobe in gap. Themis V12057009.
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
3.1.1. Direction of flow in LVF
In the mapped region, flow directions are away from the massif
walls in circumferential LDA (Fig. 3A, B) and away from valley and
crater walls in linear LDA (Fig. 3C); however, when massif/wall LDA/
LVF meet in central valley floors (Fig. 3D) or between massifs (Fig. 3E)
it merges and commonly follows the local topographic gradient to
create along-valley flow, forming complex folds and other deformation patterns (Fig. 3D). In some places, flow divides can be established
where flow patterns diverge from a local high and extend down-valley
in opposite directions (Fig. 3E, middle; Fig. 3D, lower right).
3.1.2. Detailed structure of LDA
New high-resolution THEMIS, MOC and HRSC data show much
more detail than Viking (Fig. 3B) and reveal that aprons are composed
of multiple individual lobes derived from local indentations (alcoves)
in the massif (Fig. 3B) and valley walls (Fig. 3C); pitting suggests loss
of ice by sublimation and marginal ridges are reminiscent of moraines.
Localized convex-outward ridges in the proximal parts of the aprons
(Fig. 3B, C) are similar to ridges on debris-covered glaciers (Levy et al.,
2006; Marchant et al., 2007).
3.1.3. Relationships between LDA and LVF
Where massifs face outward to plains (Fig. 3B), debris aprons
spread out as lobes from alcoves and deform in relation to their
neighbors; where they meet obstacles, they compress and flow
around the obstacles (Fig. 3C), and in some cases, where the obstacle
is parallel to the crater wall, they converge and flow through a low
point in the obstacle to create a piedmont-like lobe (Fig. 3F) and local
LVF. Where massifs are close together, LDA converge in the middle of
the valley, turn and flow laterally, often forming divides (Fig. 3E). In
some cases (Fig. 3D), LVF flows from two different valleys, converges,
incorporating a LDA from the southern valley wall, and forms a huge
broad fold more than 25 km in length that becomes part of the linear
LDA in the southern part of the valley wall (Fig. 3A). Thus, at least in
these numerous cases, LDA becomes LVF and vice versa.
3.1.4. Relationship of LDA/LVF to adjacent walls and origin of the
lubricating agent
Numerous local alcoves appear to be the source of the concentric
outward ridges that are the hallmarks of the LDA deposits (Fig. 3A–C, E–
F); these are very similar to the debris-covered glacier source alcoves seen
in the two regions interpreted to represent integrated valley glacial landsystems (Head et al., 2006a,b). Detailed HRSC topography often shows
evidence for depressions at the head of the ridges and the base of the
massifs, suggesting that ice and snow once accumulated there to form
debris-covered glaciers, but since has sublimated.
3.2. Mamers Valles (Fig. 2, location 4; Fig. 4)
Analysis of MOLA data in this area (Carr, 2001) revealed slope
reversals in Mamers Valles, a Hesperian fretted valley, suggesting
that down-valley flow of lineated terrain was minor. LDA were
interpreted by Carr (2001) as debris flows lubricated by ground ice
in material undergoing wall-slope-related mass wasting. In this area
we analyzed LDA, LVF, and their relationships along N900 km2 of the
length of Mamers Valles from the crater Cerulli north to the area just
south of Deuteronilus Colles (Fig. 1, location 4), and also assessed its
distribution in along-valley and intersecting craters (Fig. 4).
Mamers Valles can be subdivided into its lower reaches, where it
averages b10 km in width, and its upper reaches where it is 20–30 km
in width (Fig. 4A). The upper reaches are characterized by linear LDA;
high-resolution images show that LDA are composed of dozens of
parallel lobes that originate in alcoves in valley walls and extend onto
the valley floor, creating a marginal ridge, and abutting similar parallel
lobes emerging from the opposite wall (Fig. 4B). LDA can also emerge
from theater-like remnant crater rims (Fig. 4B) and from tributary
311
valleys intersecting the main valley wall (Fig. 4C); the tributaries are
commonly characterized by LVF that merges with the LDA, producing
a larger than average lobe and/or unusual pitted surface texture
(Fig. 4C). Asymmetry in LDA development is commonly observed,
with south-facing LDA more extensive. In narrower areas of the valley
floor, lobes from opposite sides meet and their distal ridges form
parallel linear ridges (Fig. 4B); in wider areas, LDA do not meet
(Fig. 4C), and unusual surface textures and features suggestive of icerelated periglacial processes are observed (Fig. 4C, D), including lobeshaped depressions trending in the same direction as the LDA lobes
(arrows in Fig. 4D). Where some LDA meet in the central part of the
valley, they are distorted along-valley (Fig. 4E) in a common flow
direction, become complexly folded (north part of Fig. 4E) and begin
to merge into LVF. In some cases (Fig. 4F) LDA derived from wall
alcoves rapidly deform, lose their individual identity and merge into
LVF. In the much narrower southern part of Mamers Valles (Fig. 4A),
LVF forms in the narrow tributaries from coalescing alcove-fed flow
and emerges into the main channel (Fig. 4G), where it joins other
tributary-fed LVF and linear channel-wall LDA, compressing and
deforming to produce ever-narrower folds until it becomes LVF. The
unusual nature of superposed impact craters (Fig. 4B, D) suggests that
the substrate contained significant ice (e.g., Kress and Head, 2008)
and that deformation has been minimal since its emplacement (Carr,
2001). Along-valley slope reversals (Carr, 2001) are caused by local
divides, where flow is away from broad accumulations in different
directions (Fig. 4A). Where narrow, along-valley integrated LVF flow
opens into a significantly larger part of the valley (such as a large
depression; Fig. 4A) the distinctive along-valley flow terminates in a
broad piedmont-like lobe (Fig. 4H), further contributing to the alongvalley variations in topography described by Carr (2001).
3.2.1. Direction of flow in LDA
LDA flow direction is normal to valley walls where valleys are wide
and LDA from opposite walls are separated (Fig. 4C) or simply abut
(Fig. 4B).
3.2.2. Relationships between the LDA and LVF
Where LDA meet and begin to merge, LDA flow direction is
distorted down-gradient (Fig. 4E); continued merging causes LDA to
compress (Fig. 4E, G), lose their individual identity (Fig. 4F), and
merge into and become true LVF (Fig. 4F–H).
3.2.3. Direction of flow in LVF
As noted by Carr (2001), topographic gradients are variable alongvalley; these topographic slope reversals commonly reflect observed
variations in LDA/LVF flow directions derived from detailed analysis of
folds and deformed surface textures (Fig. 4A). Along-valley slope
reversals tend to occur at flow divides, and distinctive slope changes
occur where LVF empties into wider depressions (Fig. 4H).
3.3. Ismeniae Fossae region (Fig. 1, location 6; Fig. 5)
In this area we analyzed LDA surrounding several isolated mesas
adjacent to the dichotomy boundary in the area (41° E, 45° N) north of
Ismeniae Fossae, the northernmost part of the dichotomy boundary.
The region is characterized by two major mesas and a series of smaller
satellite mesas and hills with surrounding LDA. The current mesa
topography is characterized by a series of bite-like 5–10 km wide
alcoves along their margins (Fig. 5A). In contrast to the broadly lobate
nature of LDA seen in Viking images, linear lobate debris aprons along
the dichotomy boundary scarp (Fig. 5A) are composed of numerous
parallel ridged lobes (Fig. 5B) emerging from alcoves in the scarp wall
(Fig. 5G) and flowing downslope, compressing and deforming to form
the broad apron seen at Viking resolution. Distal, medial, and looping
concentric ridges are common, as are pits and depressions (Fig. 5B).
Where downslope obstacles are encountered (Fig. 5G) flowlines are
312
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
313
Fig. 5. North of Ismeniae Fossae (Fig. 1): A. Topographic map of the region; 100 m contour interval. Arrows show direction of flow. Boxes show locations of panels B–H. B. Linear LDA
emerging from alcoves in the dichotomy boundary scarp; THEMIS V12356003. C. Circumferential LDA emerging from alcoves and showing flow patterns around obstacle; THEMIS
V03469007. D. Multiple LDA coalescing and flowing around obstacles; note small superposed lobe in upper center; THEMIS V13604003. E. Distal LDA flowing into a crater and
forming a piedmont-like lobe; THEMIS V12356003. F. Multiple LDA converging to form LVF; THEMIS V13579004. G. Linear LDA converging to form LVF; THEMIS V03469007. H. Linear
LDA converging and forming LVF; THEMIS V13916010.
diverted and sometimes join with LDA from other adjacent mesas. In
the circumferential LDA surrounding the mesas, similar relationships
are observed (Fig. 5C); here two major LDA lobes source in alcoves as a
series of small lobes that join together into larger lobes, extending
down to the base of the LDA. Many additional smaller lobes source in
smaller alcoves between these two and bend around the major
obstacle and rejoin distally to form portions of the broad distal LDA.
West of this area (Fig. 5A), circumferential LDA again are composed of
numerous individual lobes sourcing in alcoves of various sizes (Fig.
5D), flowing downslope as discrete, but conjoined lobes, and flowing
around obstacles (lower right) toward the adjacent lowlands (lower
left); the 4 km wide alcove in the top middle displays at least two
generations of lobes (one which extends to the distal reaches of the
LDA, and two smaller, apparently superposed lobes confined to the
Fig. 4. Mamers Valles, Northern Arabia Terra-Deuteronilus Mensae region (Fig. 1). A. Topographic map of northern Mamers Valles; contour interval 100 m. Arrows show mapped
directions of flow. Boxes show locations of panels B–H. B. LDA in northwest valley wall; THEMIS V04406006. C. LVF from emerging from tributaries and feeding LDA; THEMIS
V05542017. D. Floor texture between LDA emerging from walls on opposite sides of the valley; note arcuate depressions (arrows); THEMIS V05542017. E. LDA meeting in the valley
center and being distorted down-gradient; THEMIS V10572015. F. LDA merging and distorting down-gradient to become LVF; THEMIS V139290003. G. Narrow portion of Mamers
Valles with LVF from a tributary merging with valley wall LDA and forming folds and LVF; THEMIS V02521012. H. LVF flowing down-gradient out of the narrow part of the valley and
into a wide depression, and forming large piedmont-like lobes; THEMIS V14004008.
314
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
Fig. 6. Coloe Fossae region of Eastern Arabia Terra (Fig. 1): A. Topographic map of the Coloe Fossae region; contour interval 100 m. Boxes show locations of panels B–H. B. LDA at base
of massifs emerging from alcoves and transition into LVF; THEMIS V05341013. C. Multiple LDA flowing northward from alcoves in the dichotomy boundary scarp and merging into
linear LDA. Note smaller possibly superposed smaller lobes; THEMIS V03044003. D. Two superposed stages of LDA. Note sublimation pits and troughs; THEMIS V13204004. E. LDA
flowing around mesa and joining with mesa-related LDA; THEMIS V13204004. F. Converging LDA flowing from base of wall and out of pre-existing crater. Note sublimation pits and
troughs; THEMIS V11669003. G. Small sinuous channels emerging from the front of the LDA; NE part of F. H. Linear LDA forming LVF; note central breached fold; THEMIS V04492006.
vicinity of the alcove). LDA extending out onto adjacent lowland floors
terminate in steeper-sloped, outward-facing scarps (Fig. 5D), series of
parallel ridges reminiscent of moraines (Fig. 5B), pitted and grooved
textures (Fig. 5B–E), and where they encounter local depressions,
piedmont-like flow lobes (Fig. 5E). Where mesas are closely spaced
(Fig. 5F), LDA merge and are diverted laterally into broad folds that are
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
315
Fig. 7. Acheron Fossae region, north of Olympus Mons (Fig. 1): A. MOLA gradient map of eastern Acheron Fossae with color-coded topography. Boxes show locations of panels B–G.
Arrow opens toward perspective view in E. B. Graben, LVF and LDA. Arrow opens toward perspective view in D, and line shows profile location in C; HRSC 0037. C. MOLA altimetric
profile (orbit 13424) across B. D. Perspective view of crater in B; arrow in B shows viewing perspective. HRSC 0037 draped on MOLA. VE = 2×. E. Perspective view of piedmont-like
LDA emerging from Acheron Fossae graben. Arrow in A opens toward perspective view. THEMIS V09791029 and V01852010 draped on MOLA. VE = 2×. F. Impact crater with LDA on
southern wall and floor; HRSC 0037. G. Impact crater with LDA on southern wall and floor; HRSC 0037.
316
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
compressed and merge into LVF, flowing downslope to become broad
distal lobes; in this region, there is a topographic and flow divide
separating north- and south-flowing LDA and LVF. Evidence for an
apparently superposed LDA with abundant ridges and a distal
moraine-like feature is seen emerging from an alcove in the middle
right (Fig. 5F). In other cases where mesas are close together (Fig. 5H),
flow lines emerging from alcoves rapidly bend downslope and join
other alcove and valley tributaries, compressing and deforming to
create LVF.
Our analysis suggests that linear LDA and LVF are intimately related
in morphology and modes of origin. The very close relationship of LDA
source regions with alcoves (Fig. 5B, D, G), and the wide range of
associated features (e.g., concentric ridges (Fig. 5B, G), pits (Fig. 5B–E),
moraine-like features (Fig. 5B, D, G), piedmont-like lobes (Fig. 5E),
merging of flowlines into LVF (Fig. 5F, H), etc.) all suggest an integrated
system, beginning in alcoves and ending in distal lobes. We thus
interpret the evidence documented here to support a major role for
debris-covered glaciers. As LDA grew and coalesced (Fig. 5B–E, G), they
merged between massifs and began to flow down-gradient, forming LVF
(Fig. 5F, H), ultimately creating valley glaciers with divides (Fig. 5F, H)
and integrated glacial landsystems (e.g., Head et al., 2006a,b) (Fig. 5A).
wavy (Fig. 6H) than that typical of the more lobate LDA surrounding
mesas and more similar to LVF. Similar relationships are seen in
Acheron Fossae (described below), where viscous-flow floor texture
in flat, straight-walled graben form typical linear LDA, due to the fact
that local alcoves are minimized in the straight graben wall. This linear
LDA texture forms from LDA converging from the walls and meeting in
the center; as at Acheron, where slopes steepen, the linear LDA can
flow down-valley, often forming distal lobes. The waviness in the
lineated valley fill (Fig. 6) can often be related to small irregularities in
the graben walls. Central structures in the lineated LDA include broad
folds, some of which appear to be breached, forming axial depressions
(Fig. 6H, arrows; compare to Fig. 6E).
In cases where scarps and mesas are in close proximity, LDA forming
on opposite slopes rapidly merge and form LVF (Fig. 6B, bottom). LDA
formed in a topographically constrained area such as a sloping impact
crater interior (Fig. 6F, bottom) show evidence of compression against
the distal rim of the crater, diversion to the North, and flow out into the
surrounding region to form an LVF-like texture. The linear LDA on the
floor of Coloe Fossae (Fig. 6H) are testimony to the fact that LVF can
originate from valley walls and form LVF-like textures.
3.5. Acheron Fossae region (Fig. 1, location 14; Fig. 7)
3.4. Coloe Fossae region (Fig. 1, location 7; Fig. 6)
A distinctive region along and just south of the dichotomy boundary
is characterized by a series of narrow linear graben extending for about
200 km NW-SE (Fig. 1, point 7) (Coloe Fossae; 36–42° N 53.5–58° E). We
compared the LDA and LVF found here with areas characterized by
mesas (Ismeniae) and broad sinuous valleys (Mamers) of the fretted
terrain, and to Acheron Fossae, an area of LDA/LVF development outside
northern Arabia Terra. The scarp defining the main dichotomy boundary,
and the mesas that extend to the north, are both characterized by classic
examples of LDA. Along the scarp, LDA, seen at Viking resolution to be
broad aprons, are revealed to be characterized by multiple individual
lobes (Fig. 6B, top; Fig. 6C. bottom) extending 5–7 km from scarp
alcoves into the surrounding plains; characteristics include proximal
radial ridges, distal concentric ridges, and irregular pits and depressions
(Fig. 6B, C). In some cases (Fig. 6C, bottom) there is clear evidence of a
younger, smaller set of lobes extending 3–4 km out on top of the broader
10–12 km lobes. Along the north–south portion of the scarp (Fig. 6A, F)
LDA extend from the scarp about 16 km out into the adjacent lowlands; here there is evidence for extensive pits and irregular depressions, often following the radial and concentric ridged texture.
Similar relationships are seen along the mesas that characterize
Protonilus Mensae, the region in front of the scarp. LDA are formed of
multiple individual lobes distinctly related to alcoves (Fig. 6D) with
radial, concentric and pitted textures, with small-scale pitting
particularly abundant on the distal margins. More than one generation
of lobe formation is also suggested by the stratigraphic relationships
with a smaller (4–6 km) more distinctive set of lobes extending out
over the larger more extensive (16–18 km) lobes (Fig. 6D). At some
mesas (Fig. 6E), LDA are deflected around massifs and join LDA that
are forming from the mesa itself. Portions of the proximal parts of
these two peripheral lobes (Fig. 6E, bottom) are similar to LVF
textures; in addition, LDA extending downslope from the eastern part
of the mesa are being deformed into folds and incorporated into the
along-valley flow of the broad lobe (Fig. 6E lower right). Within the
graben of Coloe Fossae, the surface texture is much more linear and
LVF and LDA of glacial origin are common in association with the
graben and massifs (Fig. 7). Acheron Fossae are a series of arcuate
parallel graben on a rise north of Olympus Mons (217–237° E; 34–
40° N). The graben floors are characterized by viscous-flow-like features (Kronberg et al., 2006) resembling LDA and LVF. We analyzed the
floors and walls of the graben composing Acheron Fossae, examining
the viscous-flow-like features there and assessing their morphology,
topography, relation to underling topography, slope and orientation.
We also compared the graben floor structures to lobate deposits found
on the pole-facing slopes of impact craters superposed on the Acheron
Fossae region (Fig. 7A). Three types of viscous-flow features are seen
in the Acheron region and differ somewhat from the classic LDA and
LVF in Deuteronilus Mensae (Squyres, 1979); we focus on the eastern
half of Acheron (Fig. 7A) to illustrate these:
1) Linear LDA: Distinctive lobate features are observed on the graben
floor (Fig. 7B). The ridged texture of these features is generally
parallel to the graben walls and is somewhat sinuous but does not
commonly form the discrete fold-like lobes typical of many LDA
(Squyres, 1979; Lucchitta, 1984; Pierce and Crown, 2003; Head
et al., 2006a,b). The reason for this appears to be the distinctly
straight linear walls of the graben, which do not form the alcoves
that are common on sinuous valleys and their tributaries in the
Deuteronilus region (Figs. 3–6); in these areas alcoves appear to
serve as distinctive accumulations zones for snow, ice and rockfall,
and thus are the emergent point of the lobes forming the
individual folds within the broader LDA. Do the linear LDA show
significant lateral movement? Fig. 7B–D shows a 7–8 km diameter
impact crater on the floor and rim of an ~ 8 km wide graben; here,
in the perspective view (Fig. 7D), the linear LDA form on the northfacing graben wall and extend across the floor, over the rim, and
down into the impact crater over a distance of ~ 6–7 km. There is
also evidence that linear lobate debris aprons are forming on the
south-facing slopes, although they tend to be less prominent. The
nature of the linear LDA developed on the floors of Acheron Fossae
Fig. 8. A. Net ice accumulation (mm yr− 1) predicted in Mars atmospheric general circulation model simulation xref = (35°, 0.1270°, 2.5, TMG), superposed on the map by Squyres
(1979), which shows the specific location of several different types of ice-related features. LDA and LVF stand for lobate debris aprons and lineated valley fill. See also Fig. 1A, which
shows the areas of widespread glaciation documented in this and related papers. Indicated regions: 1. Tempe Terra, 2. Deuteronilus Mensae, 3. Nilosyrtis Mensae, and 4. Phlegra
Montes. B) Water ice accumulation during Ls = 180–360° period (mm). C. Water ice sublimation during the Ls = 0–180° period (mm). From Madeleine et al. (2009). D). In this
perspective view, a series of lobate viscous-flow features (lobate debris aprons and lineated valley fill) are observed along the dichotomy boundary of Mars, where the southern
highlands (background) meet the northern lowlands (foreground). Multiple lines of geologic evidence suggest that these features were formed by glacial activity. The scarp is
~1500 m high, and the scene is ~25 km across along the scarp face. Image is composed of CTX data from the Mars Reconnaissance Orbiter draped over MOLA topographic data from
Mars Global Surveyor, with no vertical exaggeration. See also Fig. 2C. CTX orbit P05_002902_2199_XI_39N306W, centered at 53.9° E, 40.6° N.
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
317
318
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
is much more similar to these developed in graben locally along
the dichotomy boundary in the Deuteronilus–Protonilus region
(e.g., Coloe Fossae; Fig. 6) than along the boundary scarp or in
channels and crater walls there (Head et al., 2006a,b; (Figs. 3–6)).
2) Lineated valley fill and piedmont-like deposits: In environments in
Acheron where slopes increase, such as in the dome-like structure
at the eastern end, structures and morphologies differ. Here, linear
debris aprons are developed in the graben but rapidly turn and
flow downslope to create lineated valley fill and, where the graben
open to the surrounding plains, large piedmont-like lobes (Fig. 7A,
E). In this perspective view, the large piedmont-like lobate debris
apron emerges from the graben, flows around an obstacle, and
spreads out into a large lobe about 30 km wide. A similar fan is
formed just to the north, from flow emerging from the wide graben
there (Fig. 7A). Thus, in these cases, linear LDA produce LVF which
in turn forms large lobes as the LVF flows downslope and out onto
the surrounding plains.
3) Post-Acheron Impact Craters: In this environment, numerous postAcheron impact craters show evidence of the same type of lobate fill
(Fig. 7F, G) as seen in the crater on the floor and wall of the graben
(Fig. 7B, D). The northern parts of these craters show interior wall
and floor textures (central uplifts, wall terraces, floor roughness)
typical of relatively fresh impact craters. The southern walls and
floor, however, are almost completely obscured by a darker smoother
material forming lobate deposits extending from the inner wall
down on to the crater floor. In detail, the deposits are characterized
by the same lobate ridged texture seen elsewhere in LDA; the lobes
also follow local topography on the crater floor (Fig. 7F, G).
3.5.1. Range of environments in which LDA occur
These occurrences broaden the longitude range in which northern
mid-latitude LDA and LVF are observed extending the range
sufficiently to suggest that the deposits may be common globally at
other similar longitudes (Fig. 1; Squyres 1979), and thus may be
related to broad climate latitudinal change rather than specific
conditions related to the dichotomy boundary scarp. These occurrences also broaden the geological setting to include additional
linear graben (see also Coloe Fossae, Fig. 6) and emphasize the
importance of occurrence inside superposed impact craters, and
north-facing slopes.
3.6. Assessment of other regions in the 30°–50° N latitude range
The presence of valley glaciers could be due to local environmental
conditions in which the accumulation of snow and ice was favored (e.g.,
Hecht, 2002). The widespread distribution of these glacial systems in the
Deuteronilus–Protonilus highland region (Fig. 1), however, suggests that
conditions were much more regional, extending across a significant
latitude band. To address the question of whether climatic conditions
conducive to glacial activity extended beyond the Deuteronilus–Protonilus region, we undertook a broad review of the remaining longitudes at
these latitudes and found abundant evidence of local and regional
Amazonian glacial deposits in the following areas (Fig. 1), including: 1)
Elysium Rise: Hecates Tholus (Fig.1, point 11): A 45 km wide depression at
the base of Hecates Tholus is host to a series of debris-covered glacial
deposits (Hauber et al., 2005). 2) Phlegra Montes (Fig.1, point 12): Debriscovered glacial deposits are located along the scarp of the montes as well
as surrounding individual massifs there (e.g., 30°–50° N, 160°–167° E)
(Safaeinili et al., 2009). Craters with concentric crater fill show evidence of
the former presence of significant thicknesses of ice (overtopping crater
rims) in this region (e.g., Dickson et al., submitted for publication). 3)
Arcadia Planitia (Fig. 1, point 13): Degraded mountains in central Arcadia
contain LDA-LVF deposits (e.g., 35°–40° N, 185°–190° E). 4) Tempe Terra
Region (Fig. 1. point 15): LVF and LDA of apparent glacial origin occur in
numerous places in the graben and mountains in this region (e.g., 45°–52°
N, 280°–300° E) (van Gasselt et al., 2002; Chuang and Crown, 2005). 4)
Instances have also been reported of remnant LDA-like features formed of
ice at even lower latitudes (Hauber et al., 2008).
4. Discussion and conclusions
The following characteristics are typical of lobate debris aprons and
lineated valley fill: 1) Lobate debris aprons (LDA) can be subdivided into
linear (along-valley walls and degraded crater walls) and circumferential (around isolated massifs); 2) LDA commonly form from numerous
parallel individual flow lobes emanating from alcove-like indentations
in massif and valley walls; 3) in some cases LVF glacial systems clearly
merge with linear LDA; 4) in some cases linear LDA derived from
opposite valley walls merge and flow down-valley; 5) in massif clusters,
circumferential LDA often meet those from adjacent massifs, merge, and
then flow downslope, forming piedmont-like lobate terminations in
the adjacent lowlands.
The relationships described and shown in Figs. 2–7 suggest that
linear LDA and LVF are intimately related in morphology and modes of
origin. Evidence of melting associated with LDA and LVF in the Arabia
Terra region is extremely rare, but in one location in this region
(Fig. 6G), several small channels are seen draining from the front of
LDA; the unusually abundant pitting in the LDA here and the frontal
pits at the location of the small channels suggests that a significant
component of ice was involved in the formation of these deposits (e.g.,
Pierce and Crown, 2003; Mangold, 2003; Li et al., 2005). Among
the hypotheses outlined above for the origin of LDA and LVF (e.g.,
groundwater-fed mobilization, ice-assisted rock creep, ice-rich landslides, rock glaciers, and debris-covered glaciers), we interpret the
evidence documented here to support a major role for debris-covered
glaciers. Formation of LDA by accumulation of snow and ice in alcoves,
and in tributaries along the flanks of valley walls led to the formation
and outward flow of glacial ice; debris falling from the talus slopes
above became concentrated and deformed to create the lineated
glacial debris cover. As LDA grew and coalesced, they merged between
massifs and in valley centers, and began to flow down-gradient,
forming LVF, ultimately creating large valley glaciers with divides,
local piedmont-type glaciers, and very large valley glacial landsystems
(Head et al., 2006a,b). The location and distribution of these features
(Fig. 1) strongly suggest regional intermontaine valley glacial systems
whose locations are dictated by topographic configurations (dichotomy boundary scarps, massifs, valleys and craters) conducive to
accumulation and preservation of snow and ice and the formation of
rock debris cover (Benn et al., 2003). Several topographic and
morphologic relationships suggest that some valley glacial systems
may be partly fed from local plateau icefields (Figs. 2C, 8).
In summary, the Deuteronilus–Protonilus region (Fig. 1) was an area
of active and very widespread glaciation during parts of the Amazonian.
The strong geomorphic similarities between lobate deposits along the
dichotomy boundary between 30° and 50° N with terrestrial cold-based
glaciers and glacial deposits has led to hypotheses for geologically recent
(Late Amazonian-age) mid-latitude glaciation (e.g., Head et al., 2006a,b).
The key to these studies has been to identify individual landscape
elements on Mars and to match them with terrestrial counterparts (e.g.,
Marchant and Head, 2007). Building on this work, the next logical step is
to integrate a landsystems approach (e.g., Evans, 2003), whereby
assemblages of landforms over wide spatial scales may be used to
deconvolve the evolution and maturation of glacial cycles on Mars. The
characteristics of these features compare quite favorably to terrestrial
counterparts that formed during the build up, maturation (glacial
overriding of mountain topography), and ultimate sublimation of
Miocene-age cold-based glaciers in the Antarctic Dry Valleys (ADV)
(Denton et al., 1993; Marchant et al., 1993). During the waning stages of
this glacial overriding event, alpine glaciers formed in the lee of emerging
nunataks and at the head of alcoves in otherwise ice-free valleys. Rockfall
along the sides of these alcoves, in concert with sublimation of dirty
ice, produced classic debris-covered glaciers (e.g., Marchant and Head,
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
2006, 2008). Some of the extant debris-covered glaciers in the ADV may
have formed during this time, as long ago as 8.1 Ma (Marchant et al.,
2002). These provide important insight into the interpretation of glacial
deposits in the northern mid-latitudes of Mars and may lead to a better
understanding of the behavior of ice sheets with time and how they
behave in the distinctive mid-latitude topography of the dichotomy
boundary.
Under what conditions might these features have formed on Mars?
Recent GCM analyses show that the major accumulations of water ice in
the equatorial regions (to form the Late Amazonian tropical mountain
glacier deposits) most likely involved precipitation and deposition
during periods of high obliquity. We examined the fate of tropical
mountain glaciers formed at ~45° obliquity (Forget et al., 2006, 2007)
following a return to lower obliquity (~35°) (Madeleine et al., 2007,
2009) and found that a meteorological consequence of this large
equatorial reservoir was the formation of a thick cloud belt in the
northern mid-latitudes of Mars. The thermodynamic state of the
atmosphere results in increased meridional circulation, a strong eastward jet during northern winter, and associated stationary planetary
waves. If the atmosphere is relatively dusty, a condition expected in
this configuration, then this new water cycle favors condensation and
precipitation and preservation of water ice in the areas described above
to depths approaching 1000 m during a ~50 ky high obliquity cycle
(Fig. 8). Guidelines from the GCMs can be used to model the snow and
ice accumulation and flow behavior in this latitude region and assess
the characteristics and evolution of accumulating ice in terms of flow
patterns (Fastook et al., 2008a,b) in a manner similar to analysis of
tropical mountain glaciers (Fastook et al., 2008b). Accumulation in
alcoves produces local downslope flow, in time leading to convergence
and coherent down-valley flow, and the formation of a well-developed
valley glacier system extending to the mouths of the major valleys. The
glaciers eventually extend out of the valleys and into the adjacent
northern lowlands, in a configuration comparable to observations of the
deposits (e.g., Fastook et al., 2008a,b). Expansion of the model clearly
shows reproduction of local flow patterns (Fastook et al., 2008a,b)
observed in images (Figs. 3–7). These analyses provide strong support
for the interpretations and help to assess the time scales and velocities
involved in the valley glaciation processes. The broad distribution of
snow and ice accumulation mapped out by the GCM simulations
(Madeleine et al., 2009) (Fig. 8A) raise the question of whether the LDA
and LVF developed solely as alpine-type valley glacial landsystems (e.g.,
Benn et al., 2003), or whether they might represent the distal valley
glacial components of higher altitude local or regional plateau glacial
landsystems (e.g., Rea and Evans, 2003). Preliminary analysis of the
relationships of the plateau margins and the valleys (Fig. 8D) suggests
that plateau icefields existed in at least some cases, and perhaps
regionally (Fig. 8).
In conclusion: 1) An array of terrestrial analogs for glacial processes
that are applicable to the range of conditions on Mars has been
developed (Marchant and Head, 2003, 2004a,b, 2006, 2007; Head and
Marchant, 2003); 2) This has been used to test for the presence of
deposits and sites of former valley glaciation and debris-covered glaciers
(cold-based ice) in two specific areas of Mars (Head et al., 2006a,b); 3)
From these analyses, general criteria for the recognition of debriscovered glacial deposits have been outlined as described above (Fig. 2);
4) Application of these criteria to the northern mid-latitudes (Fig. 1)
reveals the presence of widespread cold-based glaciation in valleys and
mountains and along scarps, in the 30°–50° N latitude band (Fig. 1); 5)
The global-scale latitudinal distribution of these deposits (Fig. 1)
suggests an extensive period in the Amazonian when ice was stable in
this latitude band; 6) A plausible explanation for this configuration is the
formation of an extended period of spin-axis obliquity at ~35°, following
the formation of tropical mountain glaciers at ~45° (Forget et al., 2006,
2007). Under these conditions, the northern mid-latitude band becomes
the locus of deposition of ice mobilized from equatorial latitudes with
sufficient accumulation to produce glaciers (Madeleine et al., 2007,
319
2009); and 7) Glacial flow models predict the general configuration and
morphology of the observed deposits interpreted to be integrated glacial
valley landsystems (Fastook et al., 2008b). Recent SHARAD data have
shown evidence for significant quantities of buried ice in mid-latitude
LDA and LVF deposits (Holt et al., 2008; Plaut et al., 2009), adding
confidence to this interpretation.
Acknowledgements
We gratefully acknowledge support from the Mars Exploration
Program Mars Express HRSC grant JPL 1237163, and the Mars Data
Analysis Program grants NNG05GQ46G and NNX07AN95G to JWH and
to the Mars Fundamental Research Program Grant NNX06AE32G to
DRM. Thanks to the HiRISE and CTX teams for use of high-resolution
image data, and to the Mars Express HRSC team for production of
high-quality digital elevation models.
References
Baker, V.R., 1982. The Channels of Mars. Univ. of Texas Press, Austin, Texas. 198 p.
Baker, V.R., 2001. Water and the Martian landscape. Nature 412, 228–236.
Baker, V.R., Strom, R.G., Gulick, V.C., Kargel, J.S., Komatsu, G., Kale, V.S., 1991. Ancient
oceans, ice sheets and hydrological cycle on Mars. Nature 352, 589–594.
Benn, D.I., Kirkbride, M.P., Owen, L.A., Brazier, V., 2003. Glaciated valley landsystems. In:
Evans, D.J.A. (Ed.), Glacial Landsystems. Edward Arnold, London, pp. 372–406.
Boulton, G.S., Eyles, N., 1979. Sedimentation by valley glaciers: a model and genetic
classification. In: Schluchter, C. (Ed.), Moraines and Varves, A. A. Balkema, Brookfield,
Vermont.
Carr, M.H., 1996. Water on Mars. Oxford University Press, Oxford. 229 p.
Carr, M.H., 2001. Mars Global Surveyor observations of martian fretted terrain. J. Geophys.
Res. 106, 23,571–23,593.
Carr, M.H., Schaber, G.G., 1977. Martian permafrost features. J. Geophys. Res. 82,
4039–4054.
Chuang, F.C., Crown, D.A., 2005. Surface characteristics and degradational history
of debris aprons in the Tempe Terra/Mareotis fossae region of Mars. Icarus 179,
24–42. doi:10.1016/j.icarus.2005.05.014.
Denton, G.H., Sugden, D.E., Marchant, D.R., Hall, B.L., Wilch, T.I.., 1993. East Antarctic
Ice Sheet sensitivity to Pliocene climatic change from a Dry Valleys perspective.
Geografiska Annaler 75A, 155–204.
Dickson, J.L., Head, J.W., Marchant, D.R., 2008. Late Amazonian glaciation at the
dichotomy boundary on Mars: evidence for glacial thickness maxima and multiple
glacial phases. Geology 36, 411–414.
Dickson, J.L., Head, J.W., Marchant, D.R., submitted for publication. Kilometer-scale ice
thicknesses in the northern mid-latitudes of Mars: evidence for crater-filling events
in the Late Amazonian near Phlegra Montes. Earth Planet. Sci. Lett.
Evans, D.J.A. (Ed.), 2003. Glacial Landsystems. Edward Arnold, London. 532 pp.
Eyles, N., 1983. The glaciated valley system. In: Eyles, N. (Ed.), Glacial Geology:
An Introduction for Engineers and Earth Scientists. Pergamon Press, New York,
p. 409.
Fastook, J.L., Head, J.W., Marchant, D.R., Forget, F., 2008a. Tropical mountain glaciers on
Mars: Altitude-dependence of ice accumulation, accumulation conditions, formation
times, glacier dynamics, and implications for planetary spin-axis/orbital history. Icarus
198, 305–317. doi:10.1016/j.icarus.2008.08.008.
Fastook, J.L., Head, J.W., Marchant, D.R., 2008b. Dichotomy boundary glaciation models:
implications for timing and glacial processes. Lunar Planet. Sci. 39 abstract 1109.
Forget, F., Haberle, R.M., Montmessin, F., Levrard, B., Head, J.W., 2006. Formation of glaciers
on Mars by atmospheric precipitation at high obliquity. Science 311, 368–371.
Forget, F., Montmessin, F., Levrard, B., Haberle, R.M., Head, J.W., Madeleine, J.-B., 2007.
Glaciers, polar caps, and ice mantling: the effect of obliquity on Martian climate.
Seventh International Conference on Mars, abstract 3028.
Gwinner, K., Scholten, F., Spiegel, M., Schmidt, R., Giese, B., Oberst, J., Jaumann, R.,
Neukum, G., HRSC Co-Investigator Team, 2005. Hochaufloesende Digitale Gelaendemodelle auf der Grundlage von Mars Express HRSC-Daten. Photogramm.
Fernerkund. Geoinf. 5, 387–394.
Hauber, E., et al., 2005. Discovery of a flank caldera and very young glacial activity at
Hecates Tholus, Mars. Nature 434, 356–361.
Hauber, E., van Gasselt, S., Chapman, M.G., Neukum, G., 2008. Geomorphic evidence for
former lobate debris aprons at low latitudes on Mars: indicators of the Martian
paleoclimate. J. Geophys. Res. 113, E02007. doi:10.1029/2007JE002897.
Head, J.W., Marchant, D.R., 2003. Cold-based mountain glaciers on Mars: western Arsia
Mons. Geology 31, 641–644.
Head, J.W., Mustard, J.F., Kreslavsky, M.A., Milliken, R.E., Marchant, D.R., 2003. Recent ice
ages on Mars. Nature 426, 797–802.
Head, J.W., et al., 2005. Tropical to mid-latitude snow and ice accumulation, flow and
glaciation on Mars. Nature 434, 346–351.
Head, J.W., Marchant, D.R., Agnew, M.C., Fassett, C.I., Kreslavsky, M.A., 2006a. Extensive
valley glacier deposits in the northern mid-latitudes of Mars: evidence for Late
Amazonian obliquity-driven climate change. Earth Planet. Sci. Lett. 241, 663–671.
Head, J.W., Nahm, A.L., Marchant, D.R., Neukum, G., 2006b. Modification of the
dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation.
Geophys. Res. Lett. 33, L08S03. doi:10.1029/2005GL024360.
320
J.W. Head et al. / Earth and Planetary Science Letters 294 (2010) 306–320
Hecht, M.H., 2002. Metastability of liquid water on Mars. Icarus 156, 373–386.
Holt, J.W., Safaeinili, A., Plaut, J., Head, J.W., Phillips, R.J., Seu, R., Kempf, S.D., Choudhary,
P., Young, D.A., Putzig, N.E., Biccari, D., Gim, Y., 2008. Radar sounding evidence for
buried glaciers in the southern mid-latitudes of Mars. Science 322, 1235–1238.
doi:10.1126/science.1164246.
Kadish, S.J., Head, J.W., Parsons, R.L., Marchant, D.R., 2008. The Ascraeus Mons fanshaped deposit: volcano-ice interactions and the climatic implications of coldbased tropical mountain glaciation. Icarus 197, 84–109. doi:10.1016/j.icarus.
2008.03.019.
Kargel, J.S., 2004. Mars: A Warmer Wetter Planet. Springer, Berlin. 557p.
Kargel, J.S., Strom, R.G., 1992. Ancient glaciation on Mars. Geology 20, 3–7.
Kochel, R.C., Baker, V.R., 1981. Backwasting and debris accumulation along Martian
escarpments, in Proceedings of the Third Colloquium on Planetary Water. State
University of New York, Buffalo, New York, pp. 53–58.
Kochel, R.C., Peake, R.T., 1984. Quantification of waste morphology in Martian fretted
terrain, in Proceedings of the Lunar and Planetary Science Conference 15. J. Geophys.
Res. (Suppl. 89), C336–C350.
Kress, A.M., Head, J.W., 2008. Ring-mold craters in lineated valley fill and lobate debris
aprons on Mars: evidence for subsurface glacial ice. Geophys. Res. Lett. 35, L23206.
doi:10.1029/2008GL035501.
Kronberg, P., Hauber, E., Schäfer, T., Grott, M., Gwinner, K., Giese, B., Masson, Ph., Neukum,
G., the HRSC Co-Investigator Team, 2006. Rifting in Acheron Fossae, Mars, observed by
the high resolution stereo camera (HRSC). Lunar Planet. Sci. 37 abstract 1661.
Laskar, J., Correia, A.C.M., Gastineau, M., Joutel, F., Levrard, B., Robutel, P., 2004. Long
term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170,
343–364.
Levy, J.S., Marchant, D.R., Head, J.W., 2006. Distribution and origin of patterned ground
on Mullins Valley debris-covered glacier, Antarctica: the roles of ice flow and
sublimation. Antarctic Sci. 18, 385–397.
Levy, J.S., Head, J.W., Marchant, D.R., 2007. Lineated valley fill and lobate debris apron
stratigraphy in Nilosyrtis Mensae, Mars: evidence for phases of glacial modification of the dichotomy boundary. J. Geophys. Res. 112, E08004. doi:10.1029/
2006JE002852.
Li, H., Robinson, M.S., Jurdy, D.M., 2005. Origin of Martian northern hemisphere midlatitude lobate debris aprons. Icarus 176, 382–394.
Lucchitta, B., 1978. Survey of cold-climate features on Mars. In: Donna R., Murphy (Ed.),
Proceedings of the Second Colloquium held 16-18 October, 1978, Hanover, NH.
Planetary Water and Polar Processes, Dartmouth College, p. 131.
Lucchitta, B.K., 1981. Mars and Earth: comparison of cold-climate features. Icarus 45,
264–303.
Lucchitta, B.K., 1984. Ice and debris in the fretted terrain, Mars. J. Geophys. Res. 89,
B409–B418.
Madeleine, J.B., Forget, F., Head, J.W., Levrard, B., Montmessin, F., 2007. Mars: a proposed
climatic scenario for northern mid-latitude glaciation. Lunar Planet. Sci. 38 abstract
1778.
Madeleine, J.-B., Forget, F., Head, J.W., Levrard, B., Montmessin, F., Millour, E., 2009.
Amazonian northern mid-latitude glaciation on Mars: A proposed climate scenario.
Icarus 203, 390–405.
Mangold, N., 2003. Geomorphic analysis of lobate debris aprons on Mars at Mars
Orbiter Camera scale: evidence for ice sublimation initiated by fractures. J. Geophys.
Res. 108, 8021–8033.
Marchant, D.R., Head, J.W., 2003. Cold-based glaciers in the western Dry Valleys of
Antarctica: terrestrial landforms and Martian analogs. Lunar Planet. Sci. 34 abstract
1245.
Marchant, D.R., Head, J.W., 2004a. Antarctic Dry Valleys: modification of rocks and soils
and implications for Mars. Lunar Planet. Sci. 35 abstract 2051.
Marchant, D.R., Head, J.W., 2004b. Microclimate zones in the Dry Valleys of Antarctica:
implications for landscape evolution and climate change on Mars. Lunar Planet. Sci.
35 abstract 1405.
Marchant, D.R., Head, J.W., 2006. Glacial landsystems on Mars: integrating landform
assemblages, glaciations, and climate cycles. Lunar Planet. Sci. 37 abstract 1422.
Marchant, D.R., Head, J.W., 2007. Antarctic Dry Valleys: microclimate zonation, variable
geomorphic processes, and implications for assessing climate change on Mars. Icarus
192, 187–222. doi:10.1016/j.icarus.2007.06.018.
Marchant, D.R., Head, J.W., 2008. Kilometer-thick ice-sheets in the northern midlatitudes in the Amazonian: analogs from the East Antarctic ice sheet and the Dry
Valleys. Lunar Planet. Sci. 39 abstract 2097.
Marchant, D.R., Denton, G.H., Swisher, C.C., 1993. Miocene-Pliocene glacial history of
Arena Valley, Quartermain Mountains, Antarctica. Geogr. Ann. (A) 75, 269–302.
Marchant, D.R., Lewis, A.R., Phillips, W.M., Moore, E.J., Souchez, R.A., Denton, G.H.,
Sugden, D.E., Potter, N., Landis, G.P., 2002. Formation of patterned ground and
sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land,
Antarctica. Geol. Soc. Am. Bull. 114, 718–730.
Marchant, D.R., Phillips, W.M., Fastook, J.L., Head, J.W., Schaefer, J.M., Shean, D.E.,
Kowalewski, D.E., 2007. Dating the world's oldest debris-covered glacier: implications for interpreting viscous-flow features on Mars. Lunar Planet. Sci. 38 abstract
1895.
McGill, G.E., 2000. Crustal history of north-central Arabia Terra, Mars. J. Geophys. Res.
105, 6945–6959.
Milkovich, S.M., Head, J.W., Marchant, D.R., 2006. Debris-covered piedmont glaciers
along the northwest flank of the Olympus Mons scarp: evidence for low-latitude ice
accumulation during the Late Amazonian of Mars. Icarus 181, 388–407.
Morgan, G.A., Head, J.W., Marchant, D.R., 2009. Lineated valley fill (LVF) and lobate
debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary
region, Mars: constraints on the extent, age, and episodicity of Amazonian glacial
events. Icarus 202, 22–38. doi:10.1016/j.icarus.2009.02.017.
Neukum, G., Jaumann, R., Hoffmann, H., Hauber, E., Head, J.W., Basilevsky, A.T., Ivanov, B.A.,
Werner, S.C., van Gasselt, S., Murray, J.B., McCord, T., 2004a. Recent and episodic
volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera.
Nature 432, 971–979.
Neukum, G., Jaumann, R., the HRSC Co-Investigator, Experiment Team, 2004b. HRSC:
the high resolution stereo camera of mars express. European Space Agency Special
Publication, ESA SP-1240, pp. 17–35.
Pierce, T.L., Crown, D.A., 2003. Morphologic and topographic analyses of debris aprons
in the eastern Hellas region, Mars. Icarus 163, 46–65.
Plaut, J.J., Safaeinili, A., Holt, J.W., Phillips, R.J., Head, J.W., Seu, R., Putzig, N.E., Frigeri, A.,
2009. Radar evidence for ice in lobate debris aprons in the mid-northern latitudes
of Mars. Geophys. Res. Lett. 36, L02203. doi:10.1029/2008GL036379.
Rea, B.R., Evans, D.J.A., 2003. Plateau icefield landsystems. In: Evans, D.J.A. (Ed.), Glacial
Landsystems. Edward Arnold, London, pp. 407–431.
Safaeinili, A., Holt, J., Plaut, J., Posiolova, L., Phillips, R., Head, J.W., Seu, R., the SHARAD
team, 2009. New radar evidence for glaciers in Mars Phlegra Montes region. Lunar
Planet. Sci. 40, 1988.
Scholten, F., Gwinner, K., Roatsch, T., Matz, K.-D., Whlisch, M., Giese, B., Oberst, J.,
Jaumann, R., Neukum, G., the HRSC Co-Investigator Team, 2005. Mars express HRSC
data processing — methods and operational aspects. Photogramm. Eng. Remote
Sensing 71, 1143–1152.
Sharp, R.P., 1973. Mars: fretted and chaotic terrains. J. Geophys. Res. 78, 4073–4083.
Shean, D.E., Head, J.W., Marchant, D.R., 2005. Origin and evolution of a cold-based tropical
mountain glacier on Mars: the Pavonis Mons fan-shaped deposit. J. Geophys. Res. 110,
E05001. doi:10.1029/2004JE002360.
Shean, D.E., Head, J.W., Fastook, J.L., Marchant, D.R., 2007. Recent glaciation at high
elevations on Arsia Mons, Mars: implications for the formation and evolution of large
tropical mountain glaciers. J. Geophys. Res. 112, E03004. doi:10.1029/2006JE002761.
Squyres, S., 1978. Martian fretted terrain: flow of erosional debris. Icarus 34, 600–613.
Squyres, S., 1979. The distribution of lobate debris aprons and similar flows on Mars.
J. Geophys. Res. 84, 8087–8096.
van Gasselt, S., Hauber, E., Jaumann, R., 2002. Morphology and topography of fretted
terrain at the dichotomy boundary in Tempe Terra, Mars: quantitative morphology
of slope aprons and mesas. Lunar Planet. Sci. 33 abstract 1856.
Williams, R.S., 1978. Geomorphic processes in Iceland and on Mars: a comparative
appraisal from orbital images. Abstr. Programs-Geol. Soc. Am. 10, 517.