Recent Gullies Research Articles

Recent gully erosion intensity in an agricultural landscape underlain by fluvioglacial sediments (NE Czechia)

AbstractInappropriate agricultural management practices combined with intense rainfall often lead to gully erosion. Knowledge of the causes and consequences of past erosion pulses is essential not only for farmers to improve land management, but also for municipalities to define infrastructure threats associated with material transport. This study comprehensively evaluates accelerated gully erosion and estimates gully transport capacity in fluvioglacial sediments left by a Pleistocene ice sheet in northeastern Czechia. Geomorphic mapping of an area of approximately 2 km2 revealed gullies up to 3.5 m wide and deep, with their heads starting at the boundaries of fields and pastures. The ground‐penetrating radar survey confirmed the presence of soil pipes contributing to gully formation due to unmaintained field drainage combined with the natural occurrence of soil pipes. Microscopic analysis and dendrogeomorphic dating of 102 cross‐sections from 28 exposed tree roots revealed 18 years of gully incision since 1985, with increased activity from 2007 to 2014. The mean incision rates ranged between 1–20 cm/year, but could reach 1 m during individual events. More intensive incisions were typical for soils with higher smectite content. The last severe erosion event in 2014 caused clogging of culverts and damage to infrastructure by transporting boulders up to 34 cm in diameter at critical flow velocities of 2.4–2.8 ms−1. Considering the predominance of human‐induced factors (e.g., current soil compaction due to grazing and failure to maintain the drainage pipe outlets), ongoing gully erosion can be expected during intense rainfall events unless appropriate agricultural or stabilization measures are addressed.

Distributions of recent gullies on hillslopes with different slopes and aspects in the Black Soil Region of Northeast China.

Gully erosion is an important environmental problem worldwide and the main process by which water and soil losses occur in the Black Soil Region (BSR) of Northeast China. At the end of 2012, 295,663 gullies were present in this region. However, few studies have examined the gullies of the Black Soil Region as a whole. Studying the distribution of recent gullies can reveal the pattern of gully distribution and can help predict their spatial development according to the soil and water conservation regionalization of China. This study examines the recorded gullies in the BSR of Northeast China, which is included in the first census of water resources in China and in six sub-regions of the soil and water conservation regionalization of China. Specifically, digital elevation model (DEM) data are combined with data on gullies occurring on hillslopes with different slopes and aspects to study the distribution of these features. The results illustrate that gully density, developing gully density, and the proportion of cutting land initially increase with increasing slope up to some threshold value, then decrease as the slope increases further. The patterns of stable gullies are divided into unimodal and bimodal types. Three patterns of gully intensity are identified. The areas and lengths of gullies are larger on sunny slopes, but larger numbers of gullies are present on shaded slopes. In addition, more space is available for gully development in the Hulun Buir hilly and plain sub-region and the Changbai Mountain-Wanda Mountain sub-region than in the other sub-regions.

The indication of Martian gully formation processes by slope–area analysis

Abstract The formation process of recent gullies on Mars is currently under debate. This study aims to discriminate between the proposed formation processes – pure water flow, debris flow and dry mass wasting – through the application of geomorphological indices commonly used in terrestrial geomorphology. High-resolution digital elevation models (DEMs) of Earth and Mars were used to evaluate the drainage characteristics of small slope sections. Data from Earth were used to validate the hillslope, debris-flow and alluvial process domains previously found for large fluvial catchments on Earth, and these domains were applied to gullied and ungullied slopes on Mars. In accordance with other studies, our results indicate that debris flow is one of the main processes forming the Martian gullies that were being examined. The source of the water is predominantly distributed surface melting, not an underground aquifer. Evidence is also presented indicating that other processes may have shaped Martian crater slopes, such as ice-assisted creep and solifluction, in agreement with the proposed recent Martian glacial and periglacial climate. Our results suggest that, within impact craters, different processes are acting on differently oriented slopes, but further work is needed to investigate the potential link between these observations and changes in Martian climate.

Sinuous gullies on Mars: Frequency, distribution, and implications for flow properties

Recent gullies on Mars are suspected to be the result of liquid‐water‐bearing flows. A formation from wet flows has been challenged by studies invoking granular (dry) flows. Our study focuses on the sinuous shapes observed for some of the recent Martian gullies. Sinuous gullies are found in locations and slopes (of 10°–15°) similar to straight gullies, and they are therefore related to the same formation processes. Numerical simulations of granular flows are performed here by introducing topographic variations such as obstacles, roughness, or slope changes that could possibly generate flow sinuosity. None of these simulations was able to reproduce sinuous shapes on a slope lower than 18° with friction angles typical of dry granular material. The only way to simulate sinuous shapes is to create small‐amplitude periodic variations of the topography of the deposit, an origin not supported by current Martian imagery. Given the presence of sinuosity in natural terrestrial debris flows, we have concluded that sinuous Martian gullies are better reproduced by liquid‐water‐bearing debris flows. Sinuous shapes in leveed flows are used to derive mechanical parameters from several Martian gullies using photoclinometry. Values in yield strength of 100–2200 Pa, velocities of 1.1–3.3 m s−1, and viscosities from 40 to 1040 Pa s are found, which are all within the range of values for terrestrial debris flows with various proportions of liquid water (20%–40%).

Groundwater discharge and gully formation on martian slopes

Young gullies and gully deposits on walls of martian craters have been cited as evidence that liquid water flowed on the surface of Mars relatively recently. Effects of variable environmental conditions at the surface of Mars are modeled and applied to the case of groundwater emergence from shallow aquifers to investigate whether groundwater is a viable source to enable the erosion of these gullies. The model includes detailed treatment of ice growth in the aquifer. Model results indicate that groundwater discharge can be maintained under the current environmental conditions if the aquifer permeability is like that of terrestrial gravel or higher, if the aquifer is 350 K or warmer, or if the aquifer is a brine with a freezing point depressed to 250 K or below. Groundwater discharge cannot be maintained for the conservative case of a cold, pure water, semi-pervious aquifer. Cold (275 K) pure water pervious (gravel) aquifers, warm (350 K) pure water semi-pervious aquifers, and cold (275 K) CaCl 2 brine semi-pervious aquifers all exhibit a dependence of discharge on season, latitude and slope orientation in our modeling. Seasonal, latitudinal and azimuthal discharge variations are strongest for cold CaCl 2 brine semi-pervious aquifers, with discharges from this aquifer type favoring equator-facing slopes at mid and high southern latitudes. At all latitudes and slope azimuths under our nominal conditions, the cold pure water pervious aquifer, the cold pure water semi-pervious aquifer and the cold CaCl 2 brine semi-pervious aquifer all freeze completely shortly after the simulations are started. Discharge restarts in the summer for the cold pure water pervious aquifer and the cold brine aquifer, but discharge does not restart for the cold pure water semi-pervious aquifer. The warm pure water semi-pervious aquifer maintains daily seeps throughout the year at all but high latitudes. In the case of the cold pure water pervious aquifer, approximately 500,000 m 3 of water could be discharged from a mid-latitude, 150-m thick aquifer with a 20-m wide seepage face orientated towards the equator or the pole after a single undermining-induced event before ice growth seals the seepage face. For a brine semi-pervious aquifer with the same dimensions, 200–300 m 3 of water could be released from a mid-latitude 20-m wide equator-facing seepage face before the fresh exposure is sealed for the fall and winter seasons. Our results do not rule out groundwater emergence as a means of creating some recent gullies, but they indicate that rather special and perhaps unusual conditions would be required.

New and recent gully activity on Mars as seen by HiRISE

Fresh‐appearing gully deposits are found at tens of sites in the southern hemisphere of Mars. These deposits have latitudinal and azimuthal dependences similar to the overall preferences of southern‐hemisphere gullies, suggesting that most gullies can undergo such events. Definite changes are seen at ten sites, including two previously reported. These include visible modification of gully channels and aprons. Those formation intervals constrained to better than one Mars year tend to include winter and exclude summer, suggesting seasonal activity. This seasonal activity is consistent with proposed models for gully formation driven by CO2 frost, although at least some of the new deposits are probably due to dry granular flow with no volatile involvement. As these deposits are capable of effecting distinct topographic changes to gully aprons and channels, they represent a significant component of recent gully evolution.

Possible liquid water origin for Atacama Desert mudflow and recent gully deposits on Mars

Evidence of recent gully activity on Mars has been reported based on the formation of new light toned deposits within the past decade, the origin of which remains controversial. Analogous recent light toned gully features have formed by liquid water activity in the Atacama Desert on Earth. These terrestrial deposits leave no mineralogical trace of water activity but rather show an albedo difference due to particle size sorting within a fine-grained mudflow. Therefore, spectral differences indicating varying mineralogy between a recent gully deposit and the surrounding terrain may not be the most relevant criteria for detecting water flow in arid environments. Instead, variation in particle size between the deposit and surrounding terrain is a possible discriminator to identify a water-based flow. We show that the Atacama deposit is similar to the observed Mars gully deposits, and both are consistent with liquid water activity. The light-toned Mars gully deposits could have formed from dry debris flows, but a liquid water origin cannot be ruled out because not all liquid water flows leave hydrated minerals behind on the surface. Therefore, the Mars deposits could be remnant mudflows that formed on Mars within the last decade.

Geologically recent gully–polygon relationships on Mars: Insights from the Antarctic Dry Valleys on the roles of permafrost, microclimates, and water sources for surface flow

We describe the morphology and spatial relationships between composite-wedge polygons and Mars-like gullies (consisting of alcoves, channels, and fans) in the hyper-arid Antarctic Dry Valleys (ADV), as a basis for understanding possible origins for martian gullies that also occur in association with polygonally patterned ground. Gullies in the ADV arise in part from the melting of atmospherically-derived, wind-blown snow trapped in polygon troughs. Snowmelt that yields surface flow can occur during peak southern hemisphere summer daytime insolation conditions. Ice-cemented permafrost provides an impermeable substrate over which meltwater flows, but does not significantly contribute to meltwater generation. Relationships between contraction crack polygons and sedimentary fans at the distal ends of gullies show deposition of fan material in polygon troughs, and dissection of fans by expanding polygon troughs. These observations suggest the continuous presence of meters-thick ice-cemented permafrost beneath ADV gullies. We document strong morphological similarities between gullies and polygons on Mars and those observed in the ADV Inland Mixed microclimate zone. On the basis of this morphological comparison, we propose an analogous, top–down melting model for the initiation and evolution of martian gullies that occur on polygonally-patterned, mantled surfaces.

A mid–late Holocene flood record from the alluvial reach of the Mahi River, Western India

Flooding of rivers in India is linked with the peak monsoons. Investigating the linkage between monsoonal patterns and flood history of various rivers is therefore of fundamental importance in the Indian context. In the present study, the slackwater deposits in the alluvial reaches of the Mahi river basin, western India have been documented. These occur in the ravines incised during the early Holocene on an alluvial surface comprising sediments of Late Pleistocene age. The slackwater deposits occur at elevations up to 20 m from the present river level and extend to about 500 m inland. The carbonate rich sediments forming the ravine cliffs have provided bank stability and the dissections in the ravines have helped in the accumulation of slackwater deposits due to backflooding of the floodwater from the main channel. Recent gullies have incised the sediments and exposed deposits related to major flood events. The best exposures of slackwater deposits have been observed at Dodka. The sediment succession of the slackwater deposits is dominated by bedsets and laminasets of silt and sand separated by colluvial sediments. Four events of flood deposition occurred during the mid to late Holocene. Two units of slackwater deposits, SWD 2 and 4 have been dated by IRSL at 4.6 ± 1 ka and 1.7 ± 0.5 ka. The stratigraphy of these deposits indicates that the first two slackwater units (SWD1 and SWD2) have resulted due to flooding in a regime of intense monsoon. The other two units, however, represent extreme high magnitude floods in a period of low average precipitation.

Gully systems under undisturbed indigenous forest, East Coast Region, New Zealand

Gully erosion is commonly associated with agricultural landscapes where vegetation clearance and farming practices increase runoff, leading to fluvial incision. However, gully erosion can also occur in forests that have undergone some form of disturbance, either natural or resulting from human impacts. This paper reports on recent gully development within areas of undisturbed indigenous forest as a result of a high magnitude rainfall event on the East Coast of New Zealand's North Island. This region, through a combination of crushed and sheared rock types, steep topography, and tectonic and climatic setting, has high natural rates of erosion, exacerbated by European deforestation in the late 19th and early 20th centuries. Sequential air photographs, spanning a 58 year period between 1939 and 1997 were used to classify and document the growth and recovery of gully systems in the 14.1 km 2 headwaters of the Mangaoporo catchment. Following a severe cyclone in 1988, with a rainfall of 535 mm, there were 21 active gully systems within the indigenous forest. On photography prior to 1988 only four gully systems were present. During this period there were 8 major rainfall events (150–250 mm). Despite further 5 rainfall events of 150–250 mm between 1988 and 1997 all gully systems showed signs of recovery, with a combined reduction in active area of 37%. The nature and location of these features is strongly influenced by lithology (orientation of jointing and bedding), and to a topographic threshold defined by catchment slope and catchment area.

Water at the Poles and in Permafrost Regions of Mars

Research Article| June 01, 2006 Water at the Poles and in Permafrost Regions of Mars Philip R. Christensen Philip R. Christensen 1Department of Geological Sciences Arizona State University Box 871404, Tempe, AZ 85287-1404, USA E-mail: phil.christensen@asu.edu Search for other works by this author on: GSW Google Scholar Author and Article Information Philip R. Christensen 1Department of Geological Sciences Arizona State University Box 871404, Tempe, AZ 85287-1404, USA E-mail: phil.christensen@asu.edu Publisher: Mineralogical Society of America First Online: 09 Mar 2017 Online ISSN: 1811-5217 Print ISSN: 1811-5209 © 2006 by the Mineralogical Society of America Elements (2006) 2 (3): 151–155. https://doi.org/10.2113/gselements.2.3.151 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Philip R. Christensen; Water at the Poles and in Permafrost Regions of Mars. Elements 2006;; 2 (3): 151–155. doi: https://doi.org/10.2113/gselements.2.3.151 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyElements Search Advanced Search Abstract The poles and mid-latitudes of Mars contain abundant water in ice caps, thick sequences of ice-rich layers, and mantles of snow. The volume of the known reservoir is ≥5 x 106 km3, corresponding to a layer ∼35 m thick over the planet. Hydrogen in subsurface H2O ice has been detected at latitudes poleward of 50°. Morphological features show downslope flow of ice-rich sediment, and recent gullies have been produced from subsurface aquifers or melting snowpacks. Variations in Mars' orbit on timescales of 50,000 to 2,000,000 years produce significant changes in climate, which result in the transport of water from the poles, where it currently resides, to the lower latitudes, where it may play a critical role in surface geology, mineralogy, and geochemistry. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Orientation and distribution of recent gullies in the southern hemisphere of Mars: Observations from High Resolution Stereo Camera/Mars Express (HRSC/MEX) and Mars Orbiter Camera/Mars Global Surveyor (MOC/MGS) data

Geologically recent small gullies on Mars display morphologies consistent with erosion by water or by debris flows. Suggested formation models are divided into two main categories: (1) groundwater or (2) melting of near‐surface ice/snow sourced from the atmosphere. We have measured location and orientation and recorded the local contexts of gullies to constrain the likely models of gully formation. More than 22,000 Mars Orbiter Camera Narrow Angle (MOC NA) and >120 Mars Express High Resolution Stereo Camera (HRSC) images in the southern hemisphere were searched for gullies. Discrete gullied slope sections with consistent orientation were recorded rather than individual gullies. Slope setting (impact crater, valley wall, etc.), location, and orientation were recorded for each slope section. More than 750 MOC images with gullies (>900 distinct gullied slope sections) and more than 40 HRSC images (>380 distinct gullied slope sections) were identified. From both MOC and HRSC, gullies were found to be most common between −30 and −50 degrees latitude and to have an overall pole facing preference. The preferred gully orientation for HRSC is southeast rather than south in MOC, owing to illumination effects that make gullies difficult to detect on south‐ to southwest‐facing slopes in HRSC. In both MOC and HRSC surveys, higher‐latitude gullies show less preference for pole facing than those at mid latitudes. Both data sets produced similar results, demonstrating that our data are reliable. We suggest that the observed latitudinal and orientation distributions of gullies show that insolation and atmospheric conditions play a key role in gully formation.

Rapid development and infilling of a buried gully under cropland, central Belgium

Analysis of contemporary and past gully erosion and infilling processes allowed to reconstruct the long-term evolution of a permanent gully system under cropland. An active and a buried gully under cropland were investigated. The recent sediment deposits within the active gully, adjacent to the buried gully, showed that the recent gully was filling in at a mean rate of 6.4 cm a − 1 . In the buried gully, several erosion and deposition phases could be identified and the type of deposited sediments revealed a complex infilling history. Charcoal, pottery and brick fragments of different sizes were found at all depths of the gully infilling. Their age indicates that the first gully incised after the midst of the 17th century, most probably in the second half of the 18th century or the early 19th century. Gully morphology and analogy with the processes in the recent gully indicate that the buried gully filled in rapidly. Overall, five cycles of cut and fill occurred in 350 years or less and four cycles even within little less than a few decades, indicating that gully development and infilling under cropland can be very rapid processes.

Formation of Martian gullies by the action of liquid water flowing under current Martian environmental conditions

Geomorphic evidence suggests that recent gullies on Mars were formed by fluvial activity. The Martian gully features are significant because their existence implies the presence of liquid water near the surface on Mars in geologically recent times. Irrespective of the ultimate source of the fluid carving the gullies, we seek to understand the behavior of this fluid after it reaches the Martian surface. We find that contrary to popular belief, the fluvially carved Martian gullies are consistent with formation conditions such as now occur on Mars, outside of the temperature‐pressure stability regime of liquid water. Our model of the action of flowing pure liquid water produces the observed gully length distribution only at surface pressures and temperatures below the triple point where liquid water simultaneously boils and freezes and thus suggests that gullies were formed under conditions similar to present‐day Mars. Our results suggest a typical flow rate of 30 m3/s to carve the gully channels. At least 0.15 km3 has flowed across the surface of Mars to carve the gully systems observed today, and this would require an aquifer recharge rate of ∼10−13–10−12 m/yr. The absence of gullies on Mars that are long enough to have been created above the triple point pressure argues that the atmospheric pressure has not been significantly larger than it is now since the origin of the gullies. This result may imply that Mars does not possess a significant reservoir of condensed CO2.

Atlantis basin, Sirenum Terrae, Mars: geological setting and astrobiological implications

The accomplishment of detailed geomorphological studies is a prerequisite for the location of regions in which the prevailing conditions in the past, or at present, may allow the development of possible life forms. The Atlantis basin, located in Sirenum Terrae, Southern hemisphere of Mars, is one of these astrobiologically interesting regions, where the existence of geological features such as ancient volcanic edifices, sedimentary deposits of an ancient lake and recent gullies seem to indicate the long-term presence of a thermal source and a water reservoir deep and stable enough to sustain biological processes. Here we describe the most relevant topographic and geomorphologic features in the region, highlighting the possibility for liquid water to have been present in the basin and outskirts in different moments of Mars' history. We also apply this analysis to an initial discussion of the influence of the hydrogeological evolution of the region in the putative development and/or survival of life forms in Atlantis basin.

Viscous flow features on the surface of Mars: Observations from high‐resolution Mars Orbiter Camera (MOC) images

A unique morphology suggestive of viscous flow of a meters‐thick surface layer was identified in high‐resolution (<10 m/pixel) Mars Orbiter Camera (MOC) images. A global survey of 13,000 MOC images resulted in the identification of 146 images exhibiting these viscous flow features. Slope angles derived from Mars Orbiter Laser Altimeter (MOLA) data, along with an experimentally derived flow law for ice, were used to estimate the shear stress and assess the plausibility that a ∼10 m thick ice‐dust mixture could produce the observed viscous deformation on timescales in agreement with the estimated age (105–107 years) of the material. Our shear stress estimates of 10−1.5–10−2.5 MPa yield strain rates on the order of 10−11–10−16 s−1, which are within the superplastic flow regime of ice. Mean annual surface temperatures, age constraints, and strain estimates show that it is possible for a meters‐thick ice‐dust mixture to undergo viscous deformation under past or present surface conditions for ice grain sizes >10 μm. The meters‐thick layer in which the viscous flow features formed is morphologically similar to a degraded meters‐thick ice‐dust surface deposit (dissected mantle terrain). Locations of the viscous flow features, dissected mantle terrain, and recent gullies are concentrated in the midlatitude regions, and all three show identical distributions as a function of latitude, with the maximum frequency of occurrence at ∼40°N and S. The strong association between these small‐scale flow features and the dissected mantle terrain, large‐scale viscous flow features, and recent gullies imply that deposition, deformation, and removal of ice‐rich materials has played an important role in the modification of the surface in the midlatitudes of Mars during the Amazonian and possibly longer.

Debris flows over sand dunes on Mars: Evidence for liquid water

This study focuses on the formation and physical properties of the gullies observed over large Martian dunes, especially those of the Russell crater (54°S, 347°W). Geomorphic features like sinuosities and connections of the channels show that gullies over dunes involve flows with a significant proportion of liquid. The occurrence of levees implies that these flows are debris flows with a yield strength characteristics of Bingham plastic materials. We apply terrestrial methods to estimate viscosity and velocity of these flows from levee size and sinuosities. We obtain average velocities in the range of 1 to 7 m s−1 and apparent viscosities of 2.8 to 46,000 Pa s, with an average at 740 Pa s, compared with the 0.001 Pa s of pure water. These viscosities and velocities are in the range of terrestrial debris flows with a proportion of 10 to 40% of H2O. These properties are typical of water‐holding debris flows but not of pure water surface runoff or CO2 driven flows. The debris flows over dunes are oriented on south‐facing slopes like other recent gullies. Meltwater from ground ice formed during a recent period of high obliquity is the more likely explanation for the formation of such flows over dunes.

Active polar gullies on Mars and the role of carbon dioxide.

The detection of geologically recent channels and gullies on Mars has been interpreted as evidence for recent water activity on this arid and cold planet. The presence of active water would have considerable implications for the history of Mars and for the potential for an active near-surface biota; however, water is not the only substance that can flow and may actually be one of the least likely candidates when the modern permafrost environment is considered. Here, a key site of recent gully and channel development on Mars is reported at 71 degrees S in Sisyphi Cavi, within the annual zone of polar CO2 ice and snow accumulation. Superposition of channel features over and/or through the defrosting CO2 snowpack shows that the channels are active at the present day and probably have fluid flows every spring during the annual defrosting. In itself, this is a significant observation as active fluid flows of any nature have not yet been proven on Mars. However, the ambient temperature at the time of gully activity appears to require a role for CO2 in the formation of the channels, rather than water. A model is proposed for gas-lubricated flow in the channels based on avalanching of CO2 snowpack and clastic debris. If similar mechanisms are responsible for all the recent gullies on Mars, then perhaps no near-surface astrobiological targets are available.

Ice jam-caused fluvial gullies and scour holes on northern river flood plains

Two anomalous fluvial landforms, gullies and scour holes, eroded into flood plains bordering meandering and braiding river channels have not been previously reported. We observed these features along the Milk River in southern Alberta, Canada, and northern Montana, USA, which has a history of frequent (50% probability of recurrence) and high-magnitude (12% probability of recurrence greater than bankfull) ice jam floods. Gullies have palmate and narrow linear shapes with open-ends downvalley and measure up to 208 m long×139 m wide×3.5 m deep (below bankfull). Channel ice jams reroute river water across meander lobes and cause headward gully erosion where flow returns to the main channel. Erosion of the most recent gully was observed during the record 1996 ice breakup flood and ice jams. Scour holes (bowl-shaped, closed depressions), eroded by water vortices beneath and between grounded ice jam blocks, measure up to 91 m long×22 m wide×4.5 m deep. Ice jam-caused gullies may be precursors to the formation of U-shaped oxbow lakes and multiple channels, common in many northern rivers.

Recent gullies on Mars and the source of liquid water

Geologic features resembling terrestrial water‐carved gullies imply that liquid water has flowed recently on the surface of Mars and challenge our views of the present‐day low‐temperature environment. We evaluate two possible mechanisms for the formation of liquid water under environmental conditions that we expect to have existed on Mars in its recent past. First, we examine the stability of ground ice in the permafrost and the potential for melting near‐surface ground ice (in the top few meters of soil) by solar heating and subsurface conduction. Second, we examine the potential for melting and refreezing of ice at shallow depths due to geothermal heating. We find that near‐surface ground ice does not reach the melting point of water under a range of conditions of soil thermophysical properties, latitudes, obliquities, and surface slopes. The atmosphere remains too dry for the ground ice to melt, even at high obliquity; instead, ice sublimates before reaching melting temperatures. However, the presence of salts in concentrations of 15–40% can adequately lower the melting point to allow melting to occur. We also find that a combination of a global average geothermal heat flux and a thick, low‐conductivity, unconsolidated regolith raises the depth of the melting isotherm to less than a few hundred meters from the surface. Orbitally induced oscillations in the mean annual surface temperature can cause freezing cycles in a confined aquifer at this depth. Freezing pressures generated are adequate to fracture ice‐cemented ground and allow water to escape to the surface, similar to the formation and evolution of terrestrial pingos in shallow permafrost. Both mechanisms are possible; however, the geothermal mechanism is consistent with the observations of the distribution of gullies, while the salty near‐surface ground ice mechanism is not. Further observational tests that can be performed with existing and future spacecraft are suggested.