| Dr. Lori Fenton
Curriculum Vitae:  Planetary scientist Lori Fenton joined the Carl Sagan Center as a Principal Investigator in 2006. She is a member of the Mars-Dunes.org Consortium, and she was awarded NASA’s Carl Sagan Fellowship for Early Career Researchers in 2006. Lori’s primary research interests include Aeolian geomorphology – how wind shapes a planetary surface – for both Mars and the Earth, recent and ongoing climate changes, and the mobility of wind-blown sand and dust. Her research makes use of many different types of data from satellites, images and spectra from visible through infrared wavelengths, and atmospheric models such as the Ames general circulation model. Her recent publications describe how dunes and dune fields record climate change on Mars, identifying the first evidence for dune migration there, and estimating how changes in surface dustiness from the 1970s through the 1990s have influenced the Red Planet’s climate. For Lori, the answers may be blowing in the wind.
Projects
Recent Climate Change on Mars
NNA06CB22A
The two different tasks to be directed by the PI addresses recent change in martian climate. The goal of the effort is to constrain and interpret observed changes in atmospheric and surficial conditions and their impact on a Mars General Circulation Model (GCM) and a ground ice model, respectively.
1. Decadal Albedo Change
In order to predict the influence of albedo change on climatic conditions, the PI will apply the Ames Mars GCM under various albedo conditions of the past and present. Several fundamental questions regarding Mars climate history will be addressed:
a. How might the differing albedos influence wind circulation patterns, surface wind stresses, dust devil formation, surface and atmospheric pressure, surface and atmospheric temperature, heat transport, seasonal CO2 condensation at the poles, and other parameters that the GCM predicts?
b. How might unmodeled processes, such as cloud formation and realistic dust transport, change GCM predictions?
c. How dramatically have the observed albedo changes influenced martian climate over the past 30 years and to what degree might this impact climate change over the past several million years?
d. Do the predicted effects of albedo change correspond with the observed changes on Mars (e.g., frequency of dust storms and dust devils, recession of seasonal polar caps)?
2. Climate change recorded in dune morphology
This work seeks to test the following hypothesis: like many terrestrial dune fields, the martian dunes of the southern mid- and high-latitudes formed under different climatic conditions, when sand was more easily mobilized by the wind. Since that time, the dunes have been locked in place by ground ice, and erosive processes have begun to degrade dune crests and slopes. The investigation of this hypothesis will impact the understanding of climate shifts, dune morphology, and climate-dependent atmospheric circulation patterns. Calculating ice table depths and measuring the quantity of sulfate-bearing materials in dune fields will not only provide information on the processes that stabilize dunes, it will also provide an independent test of the impact of such processes on thermal inertia derivations. Predicting ice table depth as a function of varying orbital parameters will be the first attempt to construct the history of sediment availability on another planet, and it is critical to determining the sediment state of dune fields on Mars. The deduction of ancient wind patterns from epochs when the ice table was too deep to restrict dune activity will produce a record of the atmospheric response to known and dated climate changes. Study of the spatial patterns of dune crest rounding and other erosional features will provide an understanding of the extent, forms, and rate of dune degradation since the dunes were last active.
Recent Climate Shifts Circulation Patterns, and Climate Driven Erosion Recorded in the Morphology of Southern Hemisphere Sand Dunes of Mars
NNX08AH48G
Although Mars is known to have experienced recent climate changes driven by variations in orbital parameters, the impact, timing, and the role of water during these changes is largely unconstrained. Clues to recent climate change are hidden in the morphology of southern hemisphere dunes. A latitudinal shift in dune morphology consistent with stabilized, inactive dunes coincides with the boundary of ground ice inferred from morphology [e.g., Mangold, 2004], Neutron Spectrometer data [Feldman et al., 2004], and a ground ice model [Mellon et al., 2004]. Equatorward of ~60º S, dune slipface crests are crisp, consistent with active dunes. Dunes poleward of this ~60º S boundary display rounded crests and appear coalesced, though deformed in a gravity-driven process.
Sand dunes must form in an environment in which wind energy is great enough to overcome the forces of both gravity and interparticle cohesion. In the high southern latitudes, ground ice is estimated to be present with a water-equivalent mass of greater than 20% (based on a twolayer model) [Feldman et al., 2004] and at a depth of less than ~0.5m [Mellon et al., 2004]. This work seeks to test the following hypothesis: like many terrestrial dune fields, the martian dunes of the southern mid- and high-latitudes formed under different climatic conditions, when sand was more easily mobilized by the wind. Since that time, the dunes have been locked in place by ground ice, and erosive processes have begun to degrade dune crests and slopes. The investigation of this hypothesis will impact the understanding of climate shifts, dune morphology, and climate-dependent atmospheric circulation patterns. Calculating ice table depths and measuring the quantity of sulfate-bearing materials in dune fields will not only provide information on the processes that stabilize dunes, it will also provide an independent test of the impact of such processes on thermal inertial derivations. Predicting ice table depth as a function of varying orbital parameters will be the first attempt to construct the history of sediment availability on another planet, and it is critical to determining the sediment state of dune fields on Mars. The deduction of ancient wind patterns from epochs when the ice table was too deep to restrict dune activity will produce a record of the atmospheric response to known and dated climate changes. Study of the spatial patterns of dune crest rounding and other erosional features will provide an understanding of the extent, forms, and rate of dune degradation since the dunes were last active.
Characterizing Daytime Aeolian Erosion Potential on Mars Using a Turbulence-Resolving Atmospheric Model
NNX08AU36G
A primary goal of Mars science is to understand the present-day interaction between the atmospheric environment and the planet’s surface that ultimately results in climatically- and geologically-important aeolian phenomena (e.g., dust storms, dust devils, albedo changes, dune migration, surface erosion). In particular, the actual patterns of (and processes causing) particle entrainment are poorly quantified. On Mars aeolian activity is produced by a combination of local processes that operate on a spatial scale of < 10 km (e.g., dust devils, convective wind gusts) that are superimposed on (and interact with) regional and global scale dynamics (e.g., slope winds, baroclinic eddies, fronts). Although the impact of regional- and global-scale dynamics on aeolian processes have been modeled and studied in detail, the potential aeolian impact (especially during the daytime) of the complex, highly three-dimensional dry convective circulations within the planetary boundary layer is neither well-quantified nor understood, although it is suspected to be quite significant.
A Large Eddy Simulation (LES) models atmospheric circulations to a much finer resolution than general circulation models (GCMs) and mesoscale models, resolving turbulent eddies down to the resolution of the model domain (10s to 100s of meters). Using an LES, we will characterize the relative variations in daytime aeolian erosion potential on Mars caused by changes in boundary layer convective structure as a result of time-of-day, season, surface elevation, latitude, and a variety of other parameters. We will investigate the ramifications of the full aeolian potential being realized, including dust entrainment, surface abrasion, bedform activity, saltation flux, and surface albedo modification. The proposed work is designed to bridge the gap in understanding between local- and global-scale aeolian processes and to apply this knowledge to interpreting the sedimentary and climate history of Mars.
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