Planetary Volatiles
The USGS Astrogeology Science Center conducts research on planetary volatiles. Volatiles include substances that have a high vapor pressure relative to the ambient atmosphere. We study the longevity, locations and other characteristics of volatiles. More specifically:
H2O ice, snow and frost are volatiles on the Earth. We study the persistence of perennial snowfields in Colorado and Mongolia.
Mars has snow, frost and ice of CO2 and H2O. We study Martian H2O and CO2 ice and frost, as well as polar regions in general.
Our moon has H2O ice in shadowed areas. We study lunar H2O ice.
Other moons such as Titan also have volatiles, which include liquid methane and ethane.
Locations and Properties of Ice-Exposing Scarps and New Impact Craters in the Mid-Latitudes of Mars
Although ice in the Martian mid-latitudes is typically covered by a layer of dust or regolith, it is exposed in some locations by fresh impact craters or in erosional scarps. In both cases, the exposed ice is massive or excess ice with a low lithic content. We find that erosional scarps occur between 50-61 north and south latitude, and that they are concentrated in and near Milankovi crater in the
Filter Total Items: 17
The formation mechanisms for mid-latitude ice scarps on Mars
Mid-latitude exposed ice scarps have recently been identified on Mars (Dundas et al., 2018; 2021). The presence of such surface ice exposures at relatively low latitudes was itself a mystery, and the formation dynamics of such scarps have also not been explained. In this work we model the ice ablation rates of several identified mid-latitude scarps. We find that, given certain characteristics of t
Authors
Kaj E. Williams, Colin M. Dundas, Melinda A. Kahre
Martian gully activity and the gully sediment transport system
The formation process for Martian gullies is a critical unknown for understanding recent climate conditions. Leading hypotheses include formation by snowmelt in a past climate, or formation via currently active CO2 frost processes. This paper presents an expanded catalog of >300 recent flows in gullies. The results indicate that sediment transport in current gully flows moves the full range of mat
Authors
Colin M. Dundas, Susan J. Conway, Glen E. Cushing
Mass balance of two perennial snowfields: Niwot Ridge, Colorado and the Ulaan Taiga, Mongolia.
Perennial snowfields are generally receding worldwide, though the precise mechanisms causing recessions are not always well understood. Here we apply a numerical snowpack model to identify the leading factors controlling the mass balance of two perennial snowfields that have significant human interest: Arapaho glacier, located at Niwot Ridge in the Colorado Rocky Mountains (United States), and a s
Authors
Kaj E. Williams, Christopher P. McKay, Owen B. Toon, Keith S. Jennings
Past, present, and future of Mars Polar Science: Outcomes and outlook from the 7th International Conference on Mars Polar Science and Exploration
Mars Polar Science is a subfield of Mars science that encompasses all studies of the cryosphere of Mars and its interaction with the Martian environment. Every 4 yr, the community of scientists dedicated to this subfield meets to discuss new findings and debate open issues in the International Conference on Mars Polar Science and Exploration (ICMPSE). This paper summarizes the proceedings of the s
Authors
Patricio Becerra, Isaac B. Smith, Shannon M Hibbard, Chimira Andres, Jonathan Bapst, Ali Bramson, Peter Buhler, Andrea Coronato, Serina Diniega, Jeremy Emmett, Anna Grau Galofre, Clemence Herny, Melinda Kahre, J. Paul Knightly, Stefano Nerozzi, Alyssa Pascuzzo, Ganna Portyankina, Jorge Rabassa, Leslie Tamppari, Timothy N. Titus, Jennifer L Whitten, Zuriñe Yoldi
Airborne dust plumes lofted by dislodged ice blocks at Russell crater, Mars
Linear dune gullies on poleward‐facing Martian slopes are enigmatic. Formation by CO2‐ice block or snow cornice falls has been proposed based on optical imagery of bright, high‐albedo features inside gully channels. Because these features often resemble patchy frost residue rather than three‐dimensional blocks, more evidence is needed to support the ice‐block formation mechanism. Satellite imagery
Authors
Cynthia Dinwiddie, Timothy N. Titus
Widespread exposures of extensive clean shallow ice in the mid-latitudes of Mars
Although ice in the Martian midlatitudes is typically covered by a layer of dust or regolith, it is exposed in some locations by fresh impact craters or in erosional scarps. In both cases, the exposed ice is massive or excess ice with a low lithic content. We find that erosional scarps occur between 50° and 61° north and south latitude and that they are concentrated in and near Milankovič crater i
Authors
Colin M. Dundas, Michael T. Mellon, Susan J. Conway, Ingrid J. Daubar, Kaj E. Williams, Lujendra Ojha, James J. Wray, Ali Bramson, Shane Byrne, Alfred S. McEwen, Liliya Posiolova, Gunnar Speth, Donna Viola, Margaret E. Landis, Gareth A Morgan, Asmin V Pathare
Conceptual model for the removal of cold-trapped H2O ice on the Mars northern seasonal springtime polar cap
The transport of H2O ice along the retreating north polar seasonal CO2 ice cap has previously been modeled and observed. Spectral observations show that H2O ice forms on the interior of the seasonal cap, while thermal observations show these regions to be consistent with CO2 ice. Prior to the sublimation of the seasonal CO2, the observed H2O ice deposits are diminished—and because H2O ice sublimat
Authors
Timothy N. Titus, Kaj E. Williams, Glen E. Cushing
The formation of gullies on Mars today
A decade of high-resolution monitoring has revealed extensive activity in fresh Martian gullies. Flows within the gullies are diverse: they can be relatively light, neutral or dark, colourful or bland, and range from superficial deposits to 10 m-scale topographic changes. We observed erosion and transport of material within gullies, new terraces, freshly eroded channel segments, migrating sinuous
Authors
Colin M. Dundas, Alfred S. McEwen, Serina Diniega, Candice J. Hansen, Jim N. McElwaince
Exposed subsurface ice sheets in the Martian mid-latitudes
Thick deposits cover broad regions of the Martian mid-latitudes with a smooth mantle; erosion
in these regions creates scarps that expose the internal structure of the mantle.We
investigated eight of these locations and found that they expose deposits of water ice that
can be >100 meters thick, extending downward from depths as shallow as 1 to 2 meters below
the surface.The scarps are actively ret
Authors
Colin M. Dundas, Ali M Bramson, Lujendra Ojha, James J. Wray, Michael T. Mellon, Shane Byrne, Alfred S. McEwen, N. E. Putzig, Donna Viola, Sarah Sutton, E. Clark, J.W. Holt
CO2 cycle
This chapter discusses the use of models, observations, and laboratory experiments to understand the cycling of CO2 between the atmosphere and seasonal Martian polar caps. This cycle is primarily controlled by the polar heat budget, and thus the emphasis here is on its components, including solar and infrared radiation, the effect of clouds (water- and CO2-ice), atmospheric transport, and subsurfa
Authors
Timothy N. Titus, Shane Byrne, Anthony Colaprete, Francois Forget, Timothy I. Michaels, Thomas H. Prettyman
The effects of snow and salt on ice table stability in University Valley, Antarctica
The Antarctic Dry Valleys represent a unique environment where it is possible to study dry permafrost overlaying an ice-rich permafrost. In this paper, two opposing mechanisms for ice table stability in University Valley are addressed: i) diffusive recharge via thin seasonal snow deposits and ii) desiccation via salt deposits in the upper soil column. A high-resolution time-marching soil and snow
Authors
Kaj E. Williams, Jennifer L. Heldmann, Christopher P. McKay, Michael T. Mellon
Modeling the development of martian sublimation thermokarst landforms
Sublimation-thermokarst landforms result from collapse of the surface when ice is lost from the subsurface. On Mars, scalloped landforms with scales of decameters to kilometers are observed in the mid-latitudes and considered likely thermokarst features. We describe a landscape evolution model that couples diffusive mass movement and subsurface ice loss due to sublimation. Over periods of tens of
Authors
Colin M. Dundas, Shane Byrne, Alfred S. McEwen
The USGS Astrogeology Science Center conducts research on planetary volatiles. Volatiles include substances that have a high vapor pressure relative to the ambient atmosphere. We study the longevity, locations and other characteristics of volatiles. More specifically:
H2O ice, snow and frost are volatiles on the Earth. We study the persistence of perennial snowfields in Colorado and Mongolia.
Mars has snow, frost and ice of CO2 and H2O. We study Martian H2O and CO2 ice and frost, as well as polar regions in general.
Our moon has H2O ice in shadowed areas. We study lunar H2O ice.
Other moons such as Titan also have volatiles, which include liquid methane and ethane.
Locations and Properties of Ice-Exposing Scarps and New Impact Craters in the Mid-Latitudes of Mars
Although ice in the Martian mid-latitudes is typically covered by a layer of dust or regolith, it is exposed in some locations by fresh impact craters or in erosional scarps. In both cases, the exposed ice is massive or excess ice with a low lithic content. We find that erosional scarps occur between 50-61 north and south latitude, and that they are concentrated in and near Milankovi crater in the
Filter Total Items: 17
The formation mechanisms for mid-latitude ice scarps on Mars
Mid-latitude exposed ice scarps have recently been identified on Mars (Dundas et al., 2018; 2021). The presence of such surface ice exposures at relatively low latitudes was itself a mystery, and the formation dynamics of such scarps have also not been explained. In this work we model the ice ablation rates of several identified mid-latitude scarps. We find that, given certain characteristics of t
Authors
Kaj E. Williams, Colin M. Dundas, Melinda A. Kahre
Martian gully activity and the gully sediment transport system
The formation process for Martian gullies is a critical unknown for understanding recent climate conditions. Leading hypotheses include formation by snowmelt in a past climate, or formation via currently active CO2 frost processes. This paper presents an expanded catalog of >300 recent flows in gullies. The results indicate that sediment transport in current gully flows moves the full range of mat
Authors
Colin M. Dundas, Susan J. Conway, Glen E. Cushing
Mass balance of two perennial snowfields: Niwot Ridge, Colorado and the Ulaan Taiga, Mongolia.
Perennial snowfields are generally receding worldwide, though the precise mechanisms causing recessions are not always well understood. Here we apply a numerical snowpack model to identify the leading factors controlling the mass balance of two perennial snowfields that have significant human interest: Arapaho glacier, located at Niwot Ridge in the Colorado Rocky Mountains (United States), and a s
Authors
Kaj E. Williams, Christopher P. McKay, Owen B. Toon, Keith S. Jennings
Past, present, and future of Mars Polar Science: Outcomes and outlook from the 7th International Conference on Mars Polar Science and Exploration
Mars Polar Science is a subfield of Mars science that encompasses all studies of the cryosphere of Mars and its interaction with the Martian environment. Every 4 yr, the community of scientists dedicated to this subfield meets to discuss new findings and debate open issues in the International Conference on Mars Polar Science and Exploration (ICMPSE). This paper summarizes the proceedings of the s
Authors
Patricio Becerra, Isaac B. Smith, Shannon M Hibbard, Chimira Andres, Jonathan Bapst, Ali Bramson, Peter Buhler, Andrea Coronato, Serina Diniega, Jeremy Emmett, Anna Grau Galofre, Clemence Herny, Melinda Kahre, J. Paul Knightly, Stefano Nerozzi, Alyssa Pascuzzo, Ganna Portyankina, Jorge Rabassa, Leslie Tamppari, Timothy N. Titus, Jennifer L Whitten, Zuriñe Yoldi
Airborne dust plumes lofted by dislodged ice blocks at Russell crater, Mars
Linear dune gullies on poleward‐facing Martian slopes are enigmatic. Formation by CO2‐ice block or snow cornice falls has been proposed based on optical imagery of bright, high‐albedo features inside gully channels. Because these features often resemble patchy frost residue rather than three‐dimensional blocks, more evidence is needed to support the ice‐block formation mechanism. Satellite imagery
Authors
Cynthia Dinwiddie, Timothy N. Titus
Widespread exposures of extensive clean shallow ice in the mid-latitudes of Mars
Although ice in the Martian midlatitudes is typically covered by a layer of dust or regolith, it is exposed in some locations by fresh impact craters or in erosional scarps. In both cases, the exposed ice is massive or excess ice with a low lithic content. We find that erosional scarps occur between 50° and 61° north and south latitude and that they are concentrated in and near Milankovič crater i
Authors
Colin M. Dundas, Michael T. Mellon, Susan J. Conway, Ingrid J. Daubar, Kaj E. Williams, Lujendra Ojha, James J. Wray, Ali Bramson, Shane Byrne, Alfred S. McEwen, Liliya Posiolova, Gunnar Speth, Donna Viola, Margaret E. Landis, Gareth A Morgan, Asmin V Pathare
Conceptual model for the removal of cold-trapped H2O ice on the Mars northern seasonal springtime polar cap
The transport of H2O ice along the retreating north polar seasonal CO2 ice cap has previously been modeled and observed. Spectral observations show that H2O ice forms on the interior of the seasonal cap, while thermal observations show these regions to be consistent with CO2 ice. Prior to the sublimation of the seasonal CO2, the observed H2O ice deposits are diminished—and because H2O ice sublimat
Authors
Timothy N. Titus, Kaj E. Williams, Glen E. Cushing
The formation of gullies on Mars today
A decade of high-resolution monitoring has revealed extensive activity in fresh Martian gullies. Flows within the gullies are diverse: they can be relatively light, neutral or dark, colourful or bland, and range from superficial deposits to 10 m-scale topographic changes. We observed erosion and transport of material within gullies, new terraces, freshly eroded channel segments, migrating sinuous
Authors
Colin M. Dundas, Alfred S. McEwen, Serina Diniega, Candice J. Hansen, Jim N. McElwaince
Exposed subsurface ice sheets in the Martian mid-latitudes
Thick deposits cover broad regions of the Martian mid-latitudes with a smooth mantle; erosion
in these regions creates scarps that expose the internal structure of the mantle.We
investigated eight of these locations and found that they expose deposits of water ice that
can be >100 meters thick, extending downward from depths as shallow as 1 to 2 meters below
the surface.The scarps are actively ret
Authors
Colin M. Dundas, Ali M Bramson, Lujendra Ojha, James J. Wray, Michael T. Mellon, Shane Byrne, Alfred S. McEwen, N. E. Putzig, Donna Viola, Sarah Sutton, E. Clark, J.W. Holt
CO2 cycle
This chapter discusses the use of models, observations, and laboratory experiments to understand the cycling of CO2 between the atmosphere and seasonal Martian polar caps. This cycle is primarily controlled by the polar heat budget, and thus the emphasis here is on its components, including solar and infrared radiation, the effect of clouds (water- and CO2-ice), atmospheric transport, and subsurfa
Authors
Timothy N. Titus, Shane Byrne, Anthony Colaprete, Francois Forget, Timothy I. Michaels, Thomas H. Prettyman
The effects of snow and salt on ice table stability in University Valley, Antarctica
The Antarctic Dry Valleys represent a unique environment where it is possible to study dry permafrost overlaying an ice-rich permafrost. In this paper, two opposing mechanisms for ice table stability in University Valley are addressed: i) diffusive recharge via thin seasonal snow deposits and ii) desiccation via salt deposits in the upper soil column. A high-resolution time-marching soil and snow
Authors
Kaj E. Williams, Jennifer L. Heldmann, Christopher P. McKay, Michael T. Mellon
Modeling the development of martian sublimation thermokarst landforms
Sublimation-thermokarst landforms result from collapse of the surface when ice is lost from the subsurface. On Mars, scalloped landforms with scales of decameters to kilometers are observed in the mid-latitudes and considered likely thermokarst features. We describe a landscape evolution model that couples diffusive mass movement and subsurface ice loss due to sublimation. Over periods of tens of
Authors
Colin M. Dundas, Shane Byrne, Alfred S. McEwen