Glacier-like forms on Mars

Abstract

Abstract. Over 1300 glacier-like forms (GLFs) are located in Mars' mid-latitudes. These GLFs are visually similar to terrestrial valley glaciers, being predominantly composed of ice-dust mixtures and showing signs of downhill viscous deformation and of an expanded former extent. However, several fundamental aspects of their behaviour are virtually unknown, including temporal and spatial variations in mass balance, ice motion, landscape erosion and deposition, and hydrology. Here, we investigate the physical glaciology of martian GLFs. We use satellite-based images of specific examples and case studies to build on existing knowledge relating to: (i) GLF current and former extent, exemplified via a GLF located in Phlegra Montes; (ii) indicators of GLF motion, focusing on the presence of surface crevasses on several GLFs; (iii) processes of GLF debris transfer, focusing on mapping and interpreting boulder trains on one GLF located in Protonilus Mensae, the analysis of which suggests a minimum GLF flow speed of 7.5 mm a−1, and (iv) GLF hydrology, focusing on possible supraglacial gulley networks on several GLFs. On the basis of this information we summarise the current state of knowledge of the glaciology of martian GLFs and identify future research avenues.

Polyphase Mid‐Latitude Glaciation on Mars: Chronology of the Formation of Superposed Glacier‐Like Forms from Crater‐Count Dating

“…The correlation with D max is not surprising because the likelihood of observing larger craters in a given area should increase with its surface age (as well as with the size of the area). Despite the steepness of some SGLFs, the rate of resurfacing caused by internal deformation within them should be low, because we expect SGLFs to be thin (much thinner than VFFs generally) and this implies limited ice‐flow velocity. For instance, a tentative glaciological model (Karlsson et al, ), with its optimised plastic yield stress of 22 kPa and typical observed surface slope angles (15–30°, Figures c and supporting information, S38–S39), yields a ball‐park estimate for the thickness of SGLFs of only 11–24 m, which is consistent with their often concave surfaces (Hubbard et al, ). Although this estimate does not include a calculation of ice‐flow velocity (e.g., using Glen's flow law, Cuffey & Paterson, ) because the ice composition/rheology and temperature history are both uncertain, it points towards very subdued ice flow and limited reworking of their impact craters. If the SGLFs were much older than their apparent model ages, then their crater distributions would have reached near‐equilibrium, reflecting a balance of cratering and resurfacing rates.…”

“…The surface appearance of VFFs reflects the internal deformation and downslope transport of ice‐rich material (Hubbard et al, ). Flow‐parallel lineations observed on VFFs are deflected by topographic obstacles and can be traced over hundreds of kilometres (Dickson et al, ; Levy et al, ; Morgan et al, ).…”

Evidence for Multiple Superposed Fluvial Deposits Within Reuyl Crater, Mars

“…However, such a retreat leaves glacial lineations or recessional moraines (Dowdeswell et al, ), which are not observed within Reuyl (Figure ). (3) No glacier‐related landforms, such as viscous flow features, lobate debris aprons with moats (Hauber et al, ), lineated valley fills, valley‐parallel lineations (Kress et al, ), drumlins, moraines (Burr et al, ), or other glacier‐like forms (Hubbard et al, ) are observed within Reuyl. Such a lack of typical glacial landforms leads us to eliminate an esker origin for SR within Reuyl (Burr et al, ; DiBiase et al, ; Lefort et al, ).…”

Grid Mapping the Northern Plains of Mars: A New Overview of Recent Water‐ and Ice‐Related Landforms in Acidalia Planitia

“…Of special interest are landforms that have long been interpreted as results of the presence and action of water and/or ice (e.g., Kargel et al, ), a notion that was supported when high‐resolution images became available and provided evidence for the aggradation and degradation of materials in a permafrost context (e.g., Morgenstern et al, ; Séjourné et al, ). Moreover, the lowlands cover the northern part of the bihemispheric latitude belt of ~30° to ~60°, which hosts a variety of possible periglacial and glacial landforms such as thermal contraction cracks, gullies, and viscous flow features, VFF (e.g., Harrison et al, ; Hubbard et al, ; Levy et al, ; Milliken et al, ). These and other landforms such as a layered latitude‐dependent mantle (LDM; Kostama et al, ; Kreslavsky & Head, ; Mustard et al, ) may represent a morphological record of recent ice ages (Head et al, ).…”

“…The geographical distribution of water‐ and/or ice‐related landforms can provide important constraints on their formation mechanism and the past Martian climate and its evolution. While the populations of some of the landforms that are relevant for the recent volatile and climate history of Mars have been localized (e.g., Balme et al, ; Dickson et al, ; Harrison et al, ; Hubbard et al, ; Kadish et al, ; Levy et al, ), a comprehensive mapping of all of them over the entire lowlands is still missing. However, given the small scale of many such landforms and surface textures, their large number and overlapping relationship over the vast expanse of the northern lowlands, it appears inefficient to map them individually and represent the results in a traditional map.…”