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Precipitation in Mars' mid-latitudes formed Viscous Flow Features (VFFs), landforms analogous to terrestrial debris-covered glaciers, in the last 1 Gyr. Until recently, the prevailing view was that the Amazonian environment was not conducive to basal melting of VFFs. However, recent identification of VFF-linked eskers (sedimentary ridges deposited by meltwater in sub-glacial tunnels) in Phlegra Montes and Tempe Terra suggests localized basal melting has occurred. We identify two VFF-linked sinuous ridges in western Tempe Terra, which we propose are two additional eskers. To explore this hypothesis, we produce a 1:300,000 map of the geomorphology of western Tempe Terra, use impact crater counts to constrain the age of the sinuous ridges, and analyze the morphology and morphometry of the sinuous ridges. Mapping reveals a heavily deformed Noachian massif that was embayed by younger volcanic material and subsequently glaciated. The sinuous ridges lie 3–7 km from the VFF-termini and are associated with mounds which we interpret as ice-cored moraines. After considering multiple formation hypotheses (including inverted paleochannels and volcanic features) and comparing morphometries to Martian and terrestrial eskers, we suggest that both the sinuous ridges are of glacial origin and most likely eskers. This shows that basal melting of VFFs occurred at more than one location in Tempe Terra, at least transiently. Thus, our identification of two additional candidate eskers in Tempe Terra suggests that the late Amazonian thermal environment may have been more complex than previously thought and contributes to a better characterization of the recent glacial history of the region. • We present a geomorphic map of western Tempe Terra, Mars, and interpret its geologic history. • We consider multiple formation hypotheses for two sinuous ridges and analyze their morphology and morphometry. • We interpret both sinuous ridges as eskers, which formed between 220 Ma and 1 Ga due to melting of Amazonian glaciers. • Our identification of two additional eskers shows that basal melting occurred in multiplelocations in Tempe Terra. [ABSTRACT FROM AUTHOR]

Observations of Mars from the surface and from orbit suggest that erosion rates over the last ∼3 Gyr (the Amazonian) have been as slow as 10 −5 m/Myr and have been dominated by aeolian processes, while ancient (Noachian) erosion rates may have been orders of magnitude higher due to impact bombardment and fluvial activity. Amazonian-aged glacial deposits are widespread on Mars, but rates of erosion responsible for contributing debris to these remnant glacial deposits have not been constrained. Here, we calculate erosion rates during Amazonian glaciations using a catalog of mid-latitude glacial landforms coupled with observational and theoretical constraints on the duration of glaciation. These calculations suggest that erosion rates for scarps that contributed debris to glacial landforms are 4–7 orders of magnitude higher than average Amazonian rates in non-glaciated, low-slope regions. These erosion rates are similar to terrestrial cold-based glacier erosion and entrainment rates, consistent with cold-based glacier modification of parts of Mars. [ABSTRACT FROM AUTHOR]

Lobate debris apron (LDA) in the Mars' mid-latitudes substantiate extensive glaciation during the Late Amazonian. Detailed investigation of these landforms is imperative because different areas distributed at different latitudes, distinct geologic settings and varied regional topography may have responded to climate in different ways. In this study, mapping of LDA deposits in Erebus Montes region in the flat, low-lying plains of the northern mid-latitudes has been undertaken and examined at a detail previously not attempted to infer new insights on the history of extensive glaciation. LDA deposits show convex-up, steep terminus profiles consistent with typical down-gradient flow characteristics, and integrated flow patterns akin to the glacial landforms reported along the dichotomy boundary. Evidence for a broad piedmont-like lobe, down-gradient flow within a possible oblique-impact crater, and infilled craters, suggest focused localized flow and glaciation. Lobate flows emanating from small alcoves and superposed on the main LDA are not observed, which likely suggests that there is a lack of multi-stage glaciation facilitated by the alcove microclimatic conditions in the region. Linear-curvilinear ridges on the LDA deposits could be the remnant of the internal flow lineations, and are most likely produced by the sublimation of debris-rich ice. Brain-terrain textures, polygonal cracks and ring-mold craters are ubiquitous on the upper surface of LDA deposits, which provides the morphological evidence for the past accumulation of LDM in the region. Hitherto, radar-based investigations do not provide substantial evidence for the presence of extant water ice beneath LDA deposits. We find that the LDA deposits examined here are more consistent with the cold-based glacial behavior - morphological observations supports existence of the sublimation process in the region. We suggest that the derived best-fit age of ~30 Ma for the LDA deposits indicates age of the debris apron that has been mantled and the mapped LDA deposits in our study should be better represented by a broad age range of ~10–100 Ma. Together, our findings add another well-documented case to support the rapidly accumulating evidences for widespread extensive debris-covered glacial landsystems in the northern mid-latitudes of Mars in the Late Amazonian geological history. • LDA deposits in the Erebus Montes are from extensive glaciation in the Late Amazonian. • Erebus Montes lacks the morphological evidence for multi-stage glaciation. • Morphological evidence for extensive emplacement of LDM is ubiquitous on LDAs. • Crater retention age of ~30 Ma is estimated for the mantled surface of the LDA deposits. [ABSTRACT FROM AUTHOR]

The cyclicity and temporal succession of glacial-periglacial periods or epochs are keynotes of cold-climate geology on Earth. Relatively recent work within the Mars community has begun to dissect the mid- to higher-latitudinal terrain of Mars for analogical evidence of similar cold-climate cyclicity and succession. Here, we carry on with this work by focusing on the terrain immediately to the north of the Moreux impact-crater (40–44° N, 43–47° E). The crater is located in northern Arabia Terra, to the south of Protonilus Mensae. It lies astride of and postdates Mars' crustal-dichotomy. The latter is a global geological-boundary that separates the ancient southern-highlands from the relatively younger northern-lowland plains. Using cross-cutting relationships, relative stratigraphy and crater-size frequency distributions (CSFDs) we identify three glacial and two periglacial periods that are temporally intertwined and differentiated by a suite of features unique to each of these periods. For example, we report and discuss clusters of pingo-like mounds amidst ridge and trough terrain or "brain terrain". On Earth, the former are the work of freeze-thaw cycling; on Mars, the latter are thought to be glacial remnants. In turn, the brain terrain is underlain by small-sized polygons possibly formed by thermal contraction cracking and with margins underlain by degraded ice-wedges. Age estimates derived of CSFDs suggest that the polygonised terrain could as much as ~100 Ma, whereas the brain terrain and pingo-like mounds are thought to be ~1–~10 Ma. Possible terminal-moraines that intercept brain-terrain fragments point to an even more recent period of glaciation. If the CSFD age-estimates are valid, then the polygons that underlie the brain terrain and incise the basin floors of our study zone could be an order of magnitude older than most of the age estimates associated with polygonised terrain at other locations on Mars. The fact that there are two distinct periods of polygonization and periglacial activity with a wide offset of time within one relatively small study zone also highlights the extent to which the freeze-thaw cycling of water might be rooted as iteratively and as deeply in Mars' geological history as is its glaciation. • Cross-cutting relationships and relative stratigraphy show long-term intertwining of glacial and periglacial cycles • This ordering highlights the alternation and episodicity of glaciation and periglaciation in this region of Mars • Crater size-frequency distribution shows that the earliest onset of periglaciation in our study region could be ≤~100 Mya [ABSTRACT FROM AUTHOR]

In this study we address the question of whether the Tharsis rise that occupies ~25 % of the surface area of Mars was once covered by an ice cap, and the sudden ice-cap melting was responsible for the catastrophic development of the Late Hesperian (3.5-3.6 Ga) circum-Tharsis giant (>1000s km in length) outflow channels. To achieve this goal, we conducted geomorphologic mapping across the Oudemans crater basin (~125 km in diameter) at elevations of ~2.7 km to ~5.0 km and its bounding plateau plains at elevations of ~5.3 km to ~6.7 km in the central Tharsis rise. Our work shows that the Oudemans-impact-induced landforms were superposed by a suite of younger landform assemblages, which consist of horn-like peaks, arête-like ridges, cirque-like depressions, hanging-valley-like features, trim-line-like escarpments, lobate ridges, striated, pitted and hummocky terrains, and features resembling drumlins, crag-and-tails and roches moutonnées. A plateau-plain striated terrain on a hummocky surface exhibits streamlined linear ridges that are 400-2000 m wide and up to ~17 km long. The average length-width ratio (~9), shape, surface texture, and associated washboard landform pattern of the linear morphological features in the striated terrain on Mars are comparable to mega-scale glacial lineations (MSGLs) on Earth. Using well-understood Earth analogues as a guide, we interpret the post-Oudemans-impact landform assemblages to have formed during regional ice-sheet-style glaciation. We further suggest the striated terrain on the plateau plains to have been generated by a fast-moving ice stream in a regional ice sheet that filled 4-km deep Oudemans crater and covered the crater-bounding plateau plains in the central Tharsis rise. The volume of the glacier ice stored in the Oudemans crater basin alone is estimated on the order of ~200,000 km3. The shape of the inferred glacier-induced landforms and their cross-cutting relationships require early northward-flowing northward-advancing glaciation, followed by southward-flowing northward-retreating glaciation. The size-frequency distribution of the craters superposed on top of the interpreted glaciated landforms in the mapped area yields a glaciation age of ca. 3.5 Ga, coeval with the estimated age of the interpreted glacial landforms along the 2000-km long Valles Marineris trough zone east of the study area. The inferred glaciation age is also coeval with the development of the circum-Tharsis outflow channels. Although our work supports the Tharsis ice-cap hypothesis, the full extent of the ice cap within and possibly beyond the Tharsis rise remains unconstrained. • Geomorphologic mapping reveals a suite of Late Hesperian (~3.5 Ga) glacier-induced landforms at the western end of Valles Marineris in the Oudemans crater area. • A possible mega-scale glacial lineation (MSGL) terrain is present on the Tharsis plateau next to the crater basin. • Oudemans crater may have stored a total volume of 0.2 million cubic km ice volume. • The age of Tharsis glaciation from this study is coeval with that inferred along Valles Marineris supporting the Tharsis ice-cap hypothesis. • The age of Tharsis glaciation is also coeval with the formation of circum-Tharsis outflow channels, suggesting a genetic link. [ABSTRACT FROM AUTHOR]

Viscous flow features (VFF) occur in the mid-latitudes of Mars and have characteristics consistent with being glaciers. Climate models suggest that martian glaciers are cold-based systems in which meltwater has never been widely produced. VFF are common in Phlegra Montes, a mountain range in the mid-latitudes of the northern hemisphere of Mars. However, in Phlegra Montes, the presence of an esker associated with an extant Amazonian Period VFF provides evidence that warm-based glacial processes did formerly operate. The problem at the centre of this paper is that the glacial meltwater responsible for this esker could have been produced as a consequence of its setting in a graben, with locally enhanced geothermal heating having been the driver of melt, not systemic heating associated with a regional warm-based regime. Given this uncertainty, this paper aims to determine if there are indicators of more widespread warm-based glacial processes in Phlegra Montes. The paper briefly describes the distribution and characteristics of VFF across the region, before focussing on the search for key landforms considered diagnostic of erosion by warm-based glaciers. From our observations, including discriminant morphometrics, we conclude that the landscape of Phlegra Montes is indicative of widespread warm-based glacial processes, including subglacial scour, linear abrasion and the incision of subglacial meltwater channels. Our findings have significance in constraining the contexts and process environments within which liquid water has been produced during the Amazonian Period on Mars and point to several lines of future research into martian glaciation, climate and landscape evolution. • Identification of >16,000 km2 of viscous flow features (VFF) interpreted to be glaciers. • Widespread existence of landforms indicative of warm-based glacial erosion. • Liquid water was produced from glacier melt in a past phase of warm-based glaciation. • Glacier melt was more significant than previously thought. [ABSTRACT FROM AUTHOR]