Aeolis Research | Abstracts 1990s-2001

Abstracts 1990s-2001

2001

Title:	Characterization of Sand Dunes in Proctor Crater on Mars by Application of a Mesoscale Model (the Mars MM5) and by Development of a Graphical Information System (GIS)
Authors:	Fenton, L. K.; Richardson, M. I.; Bandfield, J. L.; Ward, A. W.; Albee, A. L.; Toigo, A. D.
Affiliation:	AA(California Institute of Technology, MS 150-21, Pasadena, CA 91125 United States ; lori@gps.caltech.edu), AB(California Institute of Technology, MS 150-21, Pasadena, CA 91125 United States ; mir@gps.caltech.edu), AC(Goddard Space Flight Center, MS 693.0, Greenbelt, MD 20771 United States ; jbandfield@lepvax.gsfc.nasa.gov), AD(United States Geological Survey, 2255 N Gemini Dr., Flagstaff, AZ 86001 United States ; wward@usgs.gov), AE(California Institute of Technology, MS 150-21, Pasadena, CA 91125 United States ; aalbee@caltech.edu), AF(Cornell University, 610 Space Sciences Bldg., Ithaca, NY 14853-6801 United States ; toigo@gps.caltech.edu)
Journal:	American Geophysical Union, Fall Meeting 2001, abstract #P42A-0566
Publication Date:	Dec 2001
Origin:	AGU
Keywords:	5415 Erosion and weathering, 5464 Remote sensing, 6225 Mars
Abstract Copyright:	(c) 2001: American Geophysical Union
Bibliographic Code:	2001AGUFM.P42A0566F
Abstract:	Aeolian action is most likely the dominant geologic process currently acting on the surface of Mars. Data recently acquired by the Mars Global Surveyor have provided an unprecedented opportunity to study in detail the surface features produced by aeolian activity in the area of the southern highlands west of the Hellas Basin. All available data sets have been incorporated into a Graphical Information System (GIS) in order to correlate aeolian features with data products from the Thermal Emission Spectrometer (e.g., albedo, thermal inertia, and composition) and from the Mars Orbiter Laser Altimeter (e.g., surface roughness, and elevation). In addition, a mesoscale model (the Mars MM5) has been applied over the study area to determine sand transport capacity and dominant wind directions. We present results from Proctor Crater, a large ( ~150~km diameter), prominent, and well-studied crater of the southern highlands of Mars. In the eastern portion of Proctor Crater is a dunefield that spans 60~x~35~km. It consists of what has been traditionally thought of as large ( ~1~km spacing), dark transverse dune ridges. Analysis of the GIS has led to numerous conclusions regarding the dunes of Proctor Crater. Surficial mapping of dune crests has led to the hypothesis that the dunes are not transverse (i.e., perpendicular to the dominant dune-forming wind) but that instead they are longitudinal (i.e., parallel to the resultant of multiple dune-forming winds). Mesoscale modeling supports the existence of a complex wind regime that affects the shape of the dunes and determines the state of activity of sand saltation. Close inspection of high resolution images (from the Narrow Angle camera on the Mars Orbiter Camera) reveals that the large dark dunes are surrounded by smaller ( ~30~m spacing), higher albedo duneforms with which they share a complex interaction. Compositional analysis of Proctor Crater has determined that the dark dunes are largely basaltic, more so than the basaltic highlands in which they are located. Calculations of thermal properties have led to estimates of average particle sizes and albedo values for both the dark and bright dunes. These results demonstrate the effectiveness of GIS analysis and the importance of high resolution atmospheric modeling.

Title:	Atmospheric dust, water ice, and temperature from MGS TES and Viking IRTM: An assessment of the global, seasonal, and interannual spacecraft record
Authors:	Liu, J.; Richardson, M. I.
Affiliation:	AA(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States ; ljj@gps.caltech.edu), AB(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States ; mir@gps.caltech.edu)
Journal:	American Geophysical Union, Fall Meeting 2001, abstract #P32E-02
Publication Date:	Dec 2001
Origin:	AGU
Keywords:	3309 Climatology (1620), 5409 Atmospheres: structure and dynamics, 5445 Meteorology (3346), 6225 Mars
Abstract Copyright:	(c) 2001: American Geophysical Union
Bibliographic Code:	2001AGUFM.P32E..02L
Abstract:	Over two years of Viking Infrared Thermal Mapper (IRTM) data and over a year of Mars Global Surveyor Thermal Emission Spectrometer (TES) data now provide the most solid basis for our knowledge of the contemporary Martian climate. Both instruments observed Mars in the thermal infrared, including bands diagnostic of atmospheric temperature (from the 15-micron CO2 band), atmospheric dust (from the 9-micron silicate feature), and atmospheric water ice (at 11-microns). Although the styles of data collection were quite different for the two instruments (MGS provides regular data from a low circular orbit, while Viking provided a wider range of local times and observation elevations; TES is a spectrometer, while IRTM was a 6-channel radiometer), they provide by far the strongest basis for reliable assessment of interannual climate variability. Key to this reliability is the fact that the TES data can be used to generate "equivalent" IRTM data by passing the IRTM spectral response functions over the TES spectra. This allows truly direct "apples-for-apples" comparison between the data sets, greatly reducing the possibility of confusing observational and retrieval biases for true variations in climate. For the retrieval of dust and water ice, we employ the method originally developed by T.Z. Martin [Icarus, 1986], while for air temperatures, we choose to compare the brightness temperatures in the band defined by the well-known IRTM 15-micron channel. We examine the likely biases in the IRTM 15-micron data, and compare a suggested correction [Wilson and Richardson, Icarus, 2000] with the TES observations. In discussing the interannual record of climate, we will highlight the behavior of mid-level air temperatures, the tropical cloud belt, and the variety of dust storms observed in both data sets. Where appropriate, for illustrative purposes, we will compare with results from GFDL Mars GCM.

Title:	Water Transport in the Martian Polar Atmosphere
Authors:	Toigo, A. D.; Richardson, M. I.
Affiliation:	AA(Department of Astronomy, Cornell University, Space Sciences Building, Ithaca, NY 14853 ; toigo@astro.cornell.edu), AB(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States ; mir@gps.caltech.edu)
Journal:	American Geophysical Union, Fall Meeting 2001, abstract #P12E-08
Publication Date:	Dec 2001
Origin:	AGU
Keywords:	5409 Atmospheres: structure and dynamics, 5462 Polar regions, 6225 Mars
Abstract Copyright:	(c) 2001: American Geophysical Union
Bibliographic Code:	2001AGUFM.P12E..08T
Abstract:	Global models of the Martian water cycle suggest that exchange of water with the northern residual ice cap is the key determinant of bulk atmospheric humidity. Unfortunately, pre-MGS data on the behavior of water in the northern summer polar atmosphere has been sparse, and global climate models used to simulate the water cycle are known to provide poor representation of atmospheric motions in the polar regions (due to the longitude-convergence problem). Here, we present the first study of water transport in the northern polar summer atmosphere using a Mesoscale model (the Mars MM5), which does not suffer from the polar defects evident in GCM's. We combine this analysis with newly processed TES data on the distribution of water vapor.

Title:	Nature and Stability of the Martian Seasonal Water Cycle
Authors:	Richardson, M. I.; Wilson, R. J.
Affiliation:	AA(Caltech, 150-21, Pasadena, CA 91125 United States ; mir@gps.caltech.edu), AB(GFDL, NOAA, Princeton, NJ United States ; rjw@gfdl.gov)
Journal:	American Geophysical Union, Fall Meeting 2001, abstract #P12E-07
Publication Date:	Dec 2001
Origin:	AGU
Keywords:	3367 Theoretical modeling, 5409 Atmospheres: structure and dynamics, 5462 Polar regions, 6225 Mars
Abstract Copyright:	(c) 2001: American Geophysical Union
Bibliographic Code:	2001AGUFM.P12E..07R
Abstract:	Which components control the contemporary water cycle and what is the nature of the control mechanisms? These questions are at the heart of understanding how the Martian exchangeable water budget adjusts to perturbations and changes in the climate system. Analysis of a water cycle model embedded in the GFDL Mars GCM provides a paradigm for the water cycle as a feedback system, providing information on the important control points and response times. Much information on this system derives from monitoring the evolution towards steady state--one that resembles the observed water vapour and ice cloud distributions. The most important exchange balance in the system is that between the northern polar atmosphere and the rest of the planet. As the major net source for water, the northern residual water ice cap is active during summer, in the window of time between the sublimation and recondensation of the seasonal CO2 cap. At this time, water is exported from the northern polar atmosphere at a rate determined by the mixing capacity of the atmosphere and the amount of water held in the polar atmosphere. The latter is determined by the cap surface temperature. During the remainder of the year, water is returned to the pole. This return flux is determined by the atmospheric mixing capacity and the amount of water vapour held in the tropical and winter extratropical atmosphere. Steady-state is achieved when these fluxes balance. For a given climate state (and a roughly repeatable annual cycle of mixing), the outflux and influx of polar water are controlled by separate variables. Holding the cap temperature constant, the outflux will remain constant. Any perturbation to the global water budget will result in a change in the return flux that tends to oppose the sense of the perturbation--the perturbation will be damped. In the same way, a change in cap temperature (e.g. associated with a change in albedo) will result in changed water outflow. Again, this will tend to change the non-polar water vapour budget and hence the polar water influx so as to develop a new steady-state. It is important to note that only in this case is the steady-state global humidity changed: a given cap temperature and seasonal cycle of mixing capacity specifies a bulk steady-state atmospheric humidity. In all cases, the regolith acts as a damper on the system and adjusts to the global water distribution dictated ultimately by the northern cap. The model also suggests fast adjustment times, on order decades. A number of factors can affect atmospheric mixing capacity. As climate forcing factors change (associated with obliquity or greenhouse gas loading) the mixing capacity will change--an area for future study. The current mixing capacity of the atmosphere is also different from one that would obtain without atmospheric water condensation and sedimentation. Model clouds play important roles in returning water to the residual ice cap in northern summer, and significantly altering interhemispheric transport from that which would occur without clouds. As with previous studies, the southern polar cap acts as a permanent sink for water. The model and resulting paradigm for the water cycle can be used in very preliminary studies of past climate states. Forcing the model with an obliquity of 45 deg., the seasonal water ice caps become significantly more extended, reaching into the summer hemisphere. In fact, the seasonal caps "overlap" in the northern tropics, generating a year-round surface ice belt. Much work remains to be done in understanding water ice transport and exchange processes before models of paleoclimate can be of widespread utility--of which analysis of data from MGS and future missions will be key.

Title:	The Mars Exploration Rovers: A Meteorological Tale of Four Landing Sites
Authors:	Toigo, A. D.; Richardson, M. I.
Affiliation:	AA(Cornell University), AB(California Insitute of Technology)
Journal:	American Astronomical Society, DPS Meeting #33, #27.09; Bulletin of the American Astronomical Society, Vol. 33, p.1089
Publication Date:	Nov 2001
Origin:	AAS
Abstract Copyright:	(c) 2001: American Astronomical Society
Bibliographic Code:	2001DPS....33.2709T
Abstract:	The Mars Exploration Rovers: A Meteorological Tale of Four Landing Sites In order to support landing site selection for the Mars Exploration Rovers (MER), due for launch in mid-2003, we have conducted mesoscale simulations of the meteorology at four sites using the Mars MM5 [Toigo and Richardson, 2001]. The simulations at the four diverse sites highlight interesting dynamical phenomena related to convection and topographic control of flow. The Hematite region (2S, 6W), sitting in the cratered southern plains, shows a large scale diurnal cycle of winds that are primarily tidal. Embedded within this flow during the daytime hours of peak heating are convective motions displaying classic hexagonal cellular behavior. The convection is initiated over locally high topography, but becomes detached and migrates during the late afternoon. The Gusev Crater site (15S, 175E) displays similar tidal and cellular convective behavior to the Hematite site, but also begins to show evidence for channeling of flow by Ma'adim Vallis. Persistent slope flow is also observed into and out of the crater. The Eos Chasma (13S, 41W) and Melas Chasma (9S, 77W) sites are both within the Valles Marineris system, with Eos Chasma being at the eastern end of the main canyon system. Both sites show very strong channeling of flow, with canyon floor flow in substantially different direction to that on the surrounding plains. Significant flow into and out of the canyons is also indicated in response to diurnal cycles of heating. Adding to the effects of topography is the strong contrast in thermal inertia between the canyon floor and the plains. In all cases, we gauge the predicted wind speeds and vertical shears at the landing times and locations to be quite modest, at the extreme not more than 10 m/s per km. Given the interesting flow behavior in the canyon systems, we very much hope for one of the rovers to explore the depths of Valles Marineris.

Title:	GCM simulations of the current Martian water cycle: clouds and dynamical leverage
Authors:	Rodin, A. V.; Wilson, R. J.; Richardson, M. I.
Affiliation:	AA(Space Research Institude, Moscow), AB(GFDL/NOAA), AC(Caltech)
Journal:	American Astronomical Society, DPS Meeting #33, #27.04; Bulletin of the American Astronomical Society, Vol. 33, p.1088
Publication Date:	Nov 2001
Origin:	AAS
Abstract Copyright:	(c) 2001: American Astronomical Society
Bibliographic Code:	2001DPS....33.2704R
Abstract:	A multiannual simulation of the current Martian climate has been carried out with the GFDL Mars general circulation model (MGCM) that includes atmospheric transport of dust and water, as well as microphysics and the radiative effects of water ice clouds. Simulations show good agreement with the recent water column retrievals from TES data. The apparent differences with Viking observations suggest that the MAWD data were biased by the shielding of water vapor absorption features by dust. The North tropical maximum of water column observed by TES in the perihelion season (South winter) is reproduced in the GCM simulations and coincides with the downward branch of the Hadley cell. Its counterpart in the aphelion season is missing because of the condensational cutoff of atmospheric water in the tropical upward branch of the Hadley cell that produces the aphelion season tropical cloud belt. A series of parametric sensitivity tests carried out with the model shows that both the seasonal trends and latitudinal gradients of water column are largely controlled by the intensity of Hadley circulation. In particular, in the aphelion season, a more intense circulation results in stronger latitudinal gradients and shorter period of rapid water vapor release from the North polar cap. By contrast, a weaker circulation results in smoother latitudinal extent of atmospheric water. In the equinoctial seasons when the circulation intensity is weakest, it remains responsible for the appearance of the precursor maxima of water vapor in the extratropics in the spring hemispheres. As the intensity of the Hadley circulation is sensitive to the thermal state of the atmosphere, the water cycle is, in part, controlled by the microphysical and radiative properties of water ice clouds, with sensitivity of this control channel being rather smooth. There is no evidence, however, that the adsorbing capability of the regolith has an equally important leverage on the Martian water cycle.

Title:	Fundamental Asymmetry in the Martian Circulation and Climate Resulting from the Global Topographic Dichotomy
Authors:	Richardson, M. I.; Wilson, R. J.
Affiliation:	AA(Caltech), AB(NOAA/GFDL)
Journal:	American Astronomical Society, DPS Meeting #33, #27.02; Bulletin of the American Astronomical Society, Vol. 33, p.1088
Publication Date:	Nov 2001
Origin:	AAS
Abstract Copyright:	(c) 2001: American Astronomical Society
Bibliographic Code:	2001DPS....33.2702R
Abstract:	Mars is replete with hemispheric asymmetry. Within the climate system, asymmetry is expressed by the presence of a permanent CO2 ice cap in the south and a residual water ice cap in the north; a cool, long northern summer and a warm, short southern summer; and, far more vigourous atmospheric circulation during southern summer than during northern summer. Geophysically, asymmetry is expressed by the large difference ( 5 km) in the mean elevation of the much older southern hemisphere and the younger north. It is generally accepted that the primary cause of the climatic asymmetries is the relatively large eccentricity of the Martian orbit (0.093) and the timing of perihelion just before southern summer solstice. As the argument of perihelion changes with time, it is expected that asymmetric biases in climate will cycle between the hemispheres on time-scales of 105-106 years. In this presentation, we demonstrate that a decidedly endogenic and non-time varying characteristic of Mars - the offset in planetary centre-of-mass from centre-of-figure - imparts a strong hemispherically asymmetric signature on the climate. We show that the topographic dichotomy forces an annual-average tropical circulation which is strongly biased towards the southern summer solstice, winter hemisphere cell. This bias has important implications for interhemispheric transport of water and lifting of dust. We relate the circulation bias to model predictions that in the absence of a residual CO2 ice cap, water ice would be unstable at the southern pole. Hemispheric biases in the atmospheric cycles of water ice and dust may be fundamentally linked to the distribution of Martian volatiles.

Title:	Characterization of Sand Dunes in Proctor Crater on Mars by Application of a Mesoscale Model (the Mars MM5) and by Development of a Graphical Information System (GIS)
Authors:	Fenton, L. K.; Richardson, M. I.; Bandfield, J. L.; Ward, A. W.; Albee, A. L.; Toigo, A. D.
Affiliation:	AA(Caltech), AB(Caltech), AC(Goddard Space Flight Center), AD(USGS), AE(Caltech), AF(Cornell U.)
Journal:	American Astronomical Society, DPS Meeting #33, #19.05; Bulletin of the American Astronomical Society, Vol. 33, p.1068
Publication Date:	Nov 2001
Origin:	AAS
Abstract Copyright:	(c) 2001: American Astronomical Society
Bibliographic Code:	2001DPS....33.1905F
Abstract:	Aeolian action is most likely the dominant geologic process currently acting on the surface of Mars. Data recently acquired by the Mars Global Surveyor have provided an unprecedented opportunity to study in detail the surface features produced by aeolian activity in the area of the southern highlands west of the Hellas Basin. All available data sets have been incorporated into a Graphical Information System (GIS) in order to correlate aeolian features with data products from the Thermal Emission Spectrometer (e.g., albedo, thermal inertia, and composition) and from the Mars Orbiter Laser Altimeter (e.g., surface roughness and elevation). In addition, a mesoscale model (the Mars MM5) has been applied over the study area to determine sand transport capacity and dominant wind directions. We present results from Proctor Crater, a large ( ~150 km diameter), prominent, and well-studied crater of the southern highlands of Mars. In the eastern portion of Proctor Crater is a dunefield that spans 60 x 35 km. It consists of what has been traditionally thought of as large ( ~1 km spacing), dark transverse dune ridges. Analysis of the GIS has led to numerous conclusions regarding the dunes of Proctor Crater. Surficial mapping of dune crests has led to the hypothesis that the dunes are not transverse (i.e., perpendicular to the dominant dune-forming wind) but that instead they are longitudinal (i.e., parallel to the resultant of multiple dune-forming winds). Mesoscale modeling supports the existence of a complex wind regime that affects the shape of the dunes and determines the state of activity of sand saltation. Close inspection of high resolution images (from the Narrow Angle camera on the Mars Orbiter Camera) reveals that the large dark dunes are surrounded by smaller ( ~30 m spacing), higher albedo duneforms with which they share a complex interaction. Compositional analysis of Proctor Crater has determined that the dark dunes are largely basaltic, more so than the basaltic highlands in which they are located. Calculations of thermal properties have led to estimates of average particle sizes and albedo values for both the dark and bright dunes. These results demonstrate the effectiveness of GIS analysis and the importance of high resolution atmospheric modeling. This work has been supported by the Mars Data Analysis Program.

Title:	The Origin of Bright and Dark Streaks on Mars: Using a Mars GCM to Solve the Problem
Authors:	Fenton, L. K.; Richardson, M. I.
Journal:	32nd Annual Lunar and Planetary Science Conference, March 12-16, 2001, Houston, Texas, abstract no.1995
Publication Date:	Mar 2001
Origin:	LPI
Bibliographic Code:	2001LPI....32.1995F
Abstract:	Because wind streaks are the only synoptic measurements of surface wind patterns on Mars, it is imperative to understand the origin of these features. Using GCM winds, we investigate the long-standing issue of the origin of bright and dark streaks.

Title:	Aeolian Erosional and Depositional Cycles on Mars: Initial Exploration of Surface Wind Stress for Varying Surface Pressures and Orbital Parameters with a GCM
Authors:	Richardson, M. I.; McCleese, D. J.
Journal:	32nd Annual Lunar and Planetary Science Conference, March 12-16, 2001, Houston, Texas, abstract no.1883
Publication Date:	Mar 2001
Origin:	LPI
Bibliographic Code:	2001LPI....32.1883R
Abstract:	We present results from an atmospheric model which provide insight into how surface stresses vary with atmospheric mass and discuss implications for erosion and deposition

2000

Title:	Comparison of a Mars Mesoscale Model to Martian Lander Meteorological Data
Authors:	Toigo, A. D.; Richardson, M. I.
Affiliation:	AA(Caltech), AB(Caltech)
Journal:	American Astronomical Society, DPS Meeting #32, #51.18; Bulletin of the American Astronomical Society, Vol. 32, p.1097
Publication Date:	Oct 2000
Origin:	AAS
Abstract Copyright:	(c) 2000: American Astronomical Society
Bibliographic Code:	2000DPS....32.5118T
Abstract:	The three Martian landers (Mars Pathfinder, Viking Lander 1, and Viking Lander 2) were able to collect high temporal resolution weather station data (pressure, temperature, and winds) for three different locations on the Martian surface. These data sets provide ground-truth against which modeling efforts can compare themselves. We have developed a new Martian mesoscale model, the Mars MM5, based upon the Penn State/NCAR Fifth Generation Mesoscale Model and modified for use with Mars. We will compare the modeled meteorological variables against those observed by the landers. We will show that the incorporation of high resolution topography, albedo, and thermal inertia data allow the mesoscale model to reproduce the measured atmospheric variables better than a global circulation model (GCM).

Title:	Changes in the Martian Circulation and Climate in Response to Orbital Parameter Variations
Authors:	Richardson, M. I.; Wilson, R. J.
Affiliation:	AA(California Institute of Technology), AB(Geophysical Fluid Dynamics Laboratory)
Journal:	American Astronomical Society, DPS Meeting #32, #50.05; Bulletin of the American Astronomical Society, Vol. 32, p.1092
Publication Date:	Oct 2000
Origin:	AAS
Abstract Copyright:	(c) 2000: American Astronomical Society
Bibliographic Code:	2000DPS....32.5005R
Abstract:	Martian orbital parameters are known to vary on time scales greater than 105 years. Such variations, especially in obliquity, have important consequences for the spatial distribution of solar heating of the surface and atmosphere, and hence are expected to affect some form of quasi-periodic climate change. The impact of changing obliquity on surface temperatures, and hence on volatile stability have been widely addressed. However, the changing insolation patterns should also modify the circulation of the atmosphere. As the nature and rate of volatile transport, and the vigour of dust lifting and transport from the surface are critical aspects of the climate, the circulation response to orbital variations needs to be assessed. In this presentation, we show results from the Geophysical Fluid Dynamics Laboratory (GFDL) Mars General Circulation Model (GCM) in which the orbit of Mars has been varied: obliquities between 0 and 60, perihelion passage between Ls=70 and 250, and eccentricities between 0 and 0.12. In general, the total atmosphere and cap CO2 budget is held constant (i.e. we assume no exchange with the regolith), and that the rate of dust supply into the lowest model level remains constant. The impact of these assumptions are examined. Many of the anticipated changes in circulation are found to occur as obliquity is increased from 0: The Hadley cell strength and that of the winter polar jet are found to increase; The magnitude of the seasonal CO2 cycle increases, resulting in extensive seasonal ice caps; Surface winds strengthen resulting in greater surface stresses and likely stronger dust lifting; The cycle of water becomes more vigourous, with large column vapour amounts in the polar regions corresponding to higher cap surface temperatures. However, some results contrast with expectations: Although the surface wind strengths change with orbital parameters, the mean directions tend not to, with implications for aeolian geological features; Even at low obliquity, the model does not develop a permanent CO2 ice cap at either pole (this likely reflects the fact that uniform and non-varying ice properties are gravely inadequate to realistically simulate Martian polar ices); Water ice deposits do not stabilize at the equator, even at high obliquity - instead they slosh backwards-and-forwards between the seasonal ice caps, as they do at present. We note that the southern summer Hadley circulation remains the dominant cell when integrated over the annual cycle, even when the timing of perihelion passage is varied by 180 degrees. We suggest that this reflects the greater importance of the global topographic dichotomy for the strength of the mean meridional circulation over that of eccentricity.

Title:	The Polar Regions and Martian Climate: Studies With a Global Climate Model
Authors:	Wilson, R. J.; Richardson, M. I.; Rodin, A. V.
Affiliation:	AA(Princeton Univ.), AB(California Inst. of Tech.), AC(Academy of Sciences (USSR))
Journal:	International Conference on Mars Polar Science and Exploration, p. 180
Publication Date:	Aug 2000
Origin:	STI
Keywords:	AIR LAND INTERACTIONS, MARS (PLANET), MARS SURFACE, POLAR REGIONS, CLIMATE MODELS, CLIMATE CHANGE, CLIMATOLOGY, ATMOSPHERIC GENERAL CIRCULATION MODELS, DUST, ICE, HYDROLOGICAL CYCLE
Bibliographic Code:	2000mpse.conf..180W
Abstract:	Much of the interest in the polar regions centers on the fact that they likely contain the best record of Martian climate change on time scales from years to eons. This expectation is based upon the observed occurrence of weathering product deposits and volatile reservoirs that are coupled to the climate. The interpretation of these records requires an understanding of the exchange of dust, water, and CO2 between the surface and atmosphere, and the atmospheric redistribution of these species. Here we discuss a global climate model that incorporates these elements at some level and will allow examination of the coupling between polar deposits and global climate systems to begin in earnest. Additional information is contained in the original extended abstract.

Title:	Mesoscale Simulations of Martian Polar Circulation
Authors:	Toigo, A. D.; Richardson, M. I.
Affiliation:	AA(California Inst. of Tech.), AB(California Inst. of Tech.)
Journal:	International Conference on Mars Polar Science and Exploration, p. 175
Publication Date:	Aug 2000
Origin:	STI
Keywords:	MARS (PLANET), MARS SURFACE, POLAR CAPS, POLAR REGIONS, DUST, MODELS, CONVECTION, SOUTHERN HEMISPHERE, SIMULATION
Bibliographic Code:	2000mpse.conf..175T
Abstract:	Lifting of dust requires high near-surface winds. A major problem in understanding the Mars dust cycle centers on determining the mechanism(s) generating these winds. Potential mechanisms include small-scale convective vortices (dust devils), regional slope winds, albedo and/or thermal inertia contrast (seabreeze) winds, etc. The retreating edge of the south seasonal polar cap is the observed location of numerous local dust storms. Therefore the role of the strong temperature contrast between bare ground and the CO2 ice has long been suspected of being an important generator of dust-lifting winds. The acquisition of high quality topography for the south polar regions allows for the first time simulations of the south polar circulation to be undertaken. Of equal importance is the availability of high-resolution atmospheric models and high-speed computing facilities, which allow the circulation to be inferred from the topographic (and albedo and thermal inertia) data. Additional information is contained in the original extended abstract.

Title:	Control of the Martian Water Cycle by the Northern Polar Ice Cap
Authors:	Richardson, M. I.; Wilson, R. J.
Affiliation:	AA(California Inst. of Tech.), AB(Princeton Univ.)
Journal:	International Conference on Mars Polar Science and Exploration, p. 149
Publication Date:	Aug 2000
Origin:	STI
Keywords:	WATER CIRCULATION, WATER, MARS (PLANET), MARS SURFACE, POLAR CAPS, HYDROLOGICAL CYCLE, ICE, ATMOSPHERIC GENERAL CIRCULATION MODELS, TEMPORAL DISTRIBUTION, MARS ENVIRONMENT
Bibliographic Code:	2000mpse.conf..149R
Abstract:	In order to undertake credible studies of the Martian climate at other epochs, one requirement is a mechanistic understanding of the processes controlling the water cycle. This need arises from the increasing role of atmospheric water ice and vapour as radiatively active species as global atmospheric water abundances increase. Further, a key motivation for modeling past climates is the need to understand temporal variations in the amounts, state, and locations of water. We have investigated the processes controlling the water cycle with the Geophysical Fluid Dynamics Laboratory (GFDL) Mars General Circulation Model (GCM). These simulations suggest that primary parameters controlling current global atmospheric water abundance are the albedo and thermal inertia of the northern residual water ice cap, which in turn will be controlled by the macro- and microphysical properties of the ice. Additional information is contained in the original extended abstract.

Title:	Mesoscale Simulations of Martian Polar Circulation
Authors:	Richardson, M. I.; Toigo, A. D.
Affiliation:	AA(California Inst. of Tech.), AB(California Inst. of Tech.)
Journal:	International Conference on Mars Polar Science and Exploration, p. 148
Publication Date:	Aug 2000
Origin:	STI
Keywords:	ICE, MARS (PLANET), MARS SURFACE, POLAR REGIONS, WATER, WATER CIRCULATION, HYDROLOGICAL CYCLE, ATMOSPHERIC GENERAL CIRCULATION MODELS, DUST, VAPOR PHASES, SIMULATION, THREE DIMENSIONAL MODELS
Bibliographic Code:	2000mpse.conf..148R
Abstract:	Exchange of water with the residual water ice cap at the northern pole is likely the primary mechanism controlling the water cycle and the global abundance of atmospheric water. The mechanics of this exchange lie in the mixing of water between the polar airmass immediately adjacent to the cap and the airmasses at lower latitudes. To date, the most detailed models of these transport processes have been undertaken with global three-dimensional models. However, such models are least valid in these regions due to the topology of their construction. For example in grid-point models, grid points evenly spaced in longitude become progressively more tightly packed in physical separation. This necessitates filtering of dynamical fields, which degrade and modify the circulation. Mesoscale models represent an improved tool with which to investigate the polar circulation. They are designed to simulate limited domains and can be arbitrarily centered, in this case on the pole, eliminating topological problems common to global models. The only previous mesoscale study of northern polar water transport is described by Siili et al., who examined aspects of cap edge water transport and localized water cold trapping. However, two-dimensional models, such as that used by Siili et al., are inherently of limited utility for modeling transport due to their inability to treat the true three-dimensional complexity of atmospheric mixing processes (which are of crucial importance even in the global models). We have adapted a fully three-dimensional mesoscale model to examine Martian polar water transport. The model and conversion are described by Toigo and Richardson. The model is based on the Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model version five (MM5) and is fully adapted to Mars. The northern polar cap is represented by Mars Orbiter Laser Altimeter topography, and Viking Infrared Thermal Mapper albedo and thermal inertia as reprocessed by Vasavada et al. Water ice is prescribed to exist everywhere that the albedo is above a value of 0.4. Exchange of water between the surface and atmosphere is parameterized using the surface flux scheme. Water transport in the atmosphere is implemented using the MM5 advection and diffusion schemes. Exchange of water between the vapor and ice phases in the atmosphere is implemented assuming instantaneous conversion at saturation to and from fixed ice particle sizes. More detailed microphysics may be implemented in the near future. Boundary and initial conditions for the simulations, including the spatial varying fields of atmospheric dust and water are derived from General Circulation Model (GCM) simulations with the Geophysical Fluid Dynamics Laboratory (GFDL) Mars GCM. We will present results comparing the transport fluxes of water between the northern polar- and mid-latitudes as simulated by the Mars MM5 and Mars GCM. We will describe the dominant modes of atmospheric transport, and comment on the implications for the water cycle control picture described by Richardson and Wilson.

Title:	A Two-Stream Model for the Mars Exploration Program
Authors:	Richardson, M. I.; McEwan, I. J.; Vasavada, A. R.
Affiliation:	AA(California Inst. of Tech.), AB(California Univ.), AC(California Univ.)
Journal:	Concepts and Approaches for Mars Exploration, p. 265
Publication Date:	Jul 2000
Origin:	STI
Keywords:	MARS EXPLORATION, MARS SAMPLE RETURN MISSIONS, MISSION PLANNING, MARS MISSIONS, PROJECT MANAGEMENT, MARS SURVEYOR 98 PROGRAM, EXTRATERRESTRIAL LIFE
Bibliographic Code:	2000came.work..265R
Abstract:	The Mars Exploration Program represents an unprecedented opportunity to study and explore a planet and an environment beyond our own. While this opportunity represents the most important development in planetary exploration since the initial robotic survey of the Solar System, it presents organizational and architectural challenges that have simply not been faced in the NASA robotic exploration endeavor to date. These challenges, of flying frequent, probably interrelated, missions to Mars within a moderate, flat fiscal environment, were responded to in the late 1990's by the Mars Surveyor Program. The architecture that evolved within this program became singularly motivated by the search for life and singularly focused upon a sample return mission (to be executed over many opportunities). The strategy behind this architecture sought to provide a clear rationale, develop common engineering systems, and centrally execute an ambitious technical program. We argue that the singular focus on the search for life and on the highly ambitious sample return strategy, while well motivated in terms of developing program coherence, forced the program into a non-optimal architecture and caused it to over-reach its means. We will argue that the focused and centralized nature of the program seriously limited its ability to respond to failures or successes; overly strained the program by coupling broad constituencies with a highly ambitious technical approach, and ultimately stifled competition, creativity, and responsiveness as the Announcement of Opportunity (AO) system was abandoned in favor of facility development.

Title:	The 'Why' and the 'What': The Science Focus of the Mars Exploration Program
Authors:	Richardson, M. I.; Gaidos, E. J.
Affiliation:	AA(California Inst. of Tech.), AB(California Inst. of Tech.)
Journal:	Concepts and Approaches for Mars Exploration, p. 263
Publication Date:	Jul 2000
Origin:	STI
Keywords:	MARS EXPLORATION, MISSION PLANNING, MARS MISSIONS, EXTRATERRESTRIAL LIFE, MARS SURVEYOR 98 PROGRAM, SNC METEORITES, HABITABILITY, MARS SAMPLE RETURN MISSIONS, FOSSILS
Bibliographic Code:	2000came.work..263R
Abstract:	The high-level scientific goals and themes of the Mars Exploration Program place important requirements on the nature and architecture of the program. Choices at this level impact not only the particular sequence of missions to be flown, but also the program's saleability, the extent to which the planetary science community is engaged in the program, and the ultimate value of the program both to our understanding of Mars and as a survey tool for deciding whether humans should venture there. We briefly review the history of scientific interest in Mars, through to the inception of the Mars Surveyor Program (MSP). While the MSP began as a relatively broad-based investigation of Mars, the excitement surrounding the 'discovery' of life in the Martian meteorite ALH 84001 redirected the program onto a pathway almost singularly focused on searching for fossil (or even extent) life in returned samples. We support the notion that the question of life is the single most important theme in Martian exploration. However, we argue that the approach that has evolved in the MSP--and would govern missions to be flown beyond 2001--is overly focused. This threatens the utility of the program as a means of understanding the cause and context of life's absence or presence. The rush to a yes-or-no answer on life has also placed technical strain on the program, will ultimately disenfranchise a significant fraction of the scientific community, and will seriously limit the ability of the program to 'survey' the planet for future exploration.

Title:	Adaptivity and the Architecture for a New Mars Exploration Program
Authors:	Pinder, J. D.; Richardson, M. I.
Affiliation:	AA(RAND Corp.), AB(California Inst. of Tech.)
Journal:	Concepts and Approaches for Mars Exploration, p. 251
Publication Date:	Jul 2000
Origin:	STI
Keywords:	MARS EXPLORATION, MARS MISSIONS, MISSION PLANNING, MARS SURVEYOR 98 PROGRAM, FLEXIBILITY
Bibliographic Code:	2000came.work..251P
Abstract:	In spite of recent failures, the prospects for Mars exploration remain excellent. The motivation for such optimism is, ironically, rooted in cyclical constraints that are unique to this endeavor: (1) steady annual funding of about 200 million; (2) regular launch opportunities every 26 months; (3) four to six years for the entire spacecraft development process; and (4) six to eight years for the science to unfold through instrument conception and design, and then converge through analysis and publication. These stable cycles create an important opportunity to employ an intelligent exploration strategy that is based on interactive adaptation, using past triumphs and failures to shape future missions. This stability, however, also poses a dangerous temptation to take the opposite approach: a static exploration strategy that is focused on a limited let of scientific objectives. Such an approach must, necessarily, rely on a single overarching 'best guess' as to exactly which fixed sequence of missions is the most attractive, based on a host of assumptions about the cost, technical risk, and potential scientific benefits of the options considered. This approach, however, is fundamentally flawed, even when implemented perfectly, because it does not allow lessons learned over time from both successes and failures to be incorporated into subsequent missions.

Title:	Global Martian Sand Transport as Predicted by the GDFL Mars GCM
Authors:	Fenton, L. K.; Richardson, M. I.
Journal:	31st Annual Lunar and Planetary Science Conference, March 13-17, 2000, Houston, Texas, abstract no. 2072
Publication Date:	Mar 2000
Origin:	LPI
Bibliographic Code:	2000LPI....31.2072F
Abstract:	Not Available

Title:	Advances in Understanding of the Martian Climate
Authors:	Richardson, M. I.
Affiliation:	AA(California Institute of Technology, USA)
Journal:	Highlights of Planetary Exploration from Space and from Earth, 24th meeting of the IAU, Joint Discussion 12, August 2000, Manchester, England, meeting abstract.
Publication Date:	n/a 2000
Origin:	AUTHOR
Bibliographic Code:	2000IAUJD..12E..16R
Abstract:	Data collected by the Viking mission to Mars resulted in a picture of the Martian climate which stood largely unmodified for over a decade. When a challenge did come in the mid-1990's it resulted from ground-based and HST observations which suggested lower global-average temperatures and dust opacities, and more atmospheric water ice than inferred from Viking. These observations prompted suggestions of climate change orders of magnitude larger and faster than anything contemplated for the Earth. A combination of new data from the Mars Global Surveyor Thermal Emission Spectrometer (TES) and reanalysis of Viking-era data have resulted in a new picture of the Martian climate. It is now clear that no significant climate change has occurred and that the ``cooler and cloudier'' conditions observed in the 1990's for northern summer applied equally well to the Viking era. TES observations have provided detailed information on the cycle of air temperature and water ice clouds which support and extend the ground-based and HST observations. The disagreement with Viking observations has been found to result from faults in the Viking Orbiter Infrared Thermal Mapper (IRTM) 15 μm channel, the lack of analysis of IRTM data applicable to water ice, and the misinterpretation of Viking Lander opacity measurements. The TES observations provide a rich data base which is now allowing a new picture of the Martian climate to be constructed in which water vapour and water ice clouds may play a significant role in modulating the annual cycles of dust and air temperature.

1990s

Title:	Polar CAP Edge Circulations in a 3D Martian Mesoscale Model
Authors:	Toigo, A. D.; Richardson, M. I.
Affiliation:	AA(California Institute of Technology), AB(California Institute of Technology)
Journal:	American Astronomical Society, DPS meeting #31, #48.01
Publication Date:	Sep 1999
Origin:	AAS
Abstract Copyright:	(c) 1999: American Astronomical Society
Bibliographic Code:	1999DPS....31.4801T
Abstract:	The Martian cap edge region is characterized by high surface winds which are driven by the large surface thermal contrast. For this study we have converted the NCAR MM5V2 mesoscale model to Mars. The model includes atmospheric dust, representation of the polar ice cap, detailed topography, thermal and albedo maps derived by Vasavada et al. (1999), and boundary conditions provided by the GFDL Mars Global Circulation Model (MGCM). We will show time evolving circulation patterns for a range of different thermal contrasts and different seasons.

Title:	The Coupled Roles of Dust and Water Ice Clouds in the Mars Aphelion Season
Authors:	Rodin, A. V.; Wilson, R. J.; Clancy, R. T.; Richardson, M. I.
Journal:	The Fifth International Conference on Mars, July 19-24, 1999, Pasadena, California, abstract no. 6235
Publication Date:	Jul 1999
Origin:	LPI
Bibliographic Code:	1999ficm.conf.6235R
Abstract:	Not Available

Title:	Comparison of Mars GCM Dust Storm Simulations with Viking Mission Observations
Authors:	Wilson, R. J.; Richardson, M. I.
Journal:	The Fifth International Conference on Mars, July 19-24, 1999, Pasadena, California, abstract no. 6234
Publication Date:	Jul 1999
Origin:	LPI
Bibliographic Code:	1999ficm.conf.6234W
Abstract:	Not Available

Title:	Seasonal Variation of Aerosols
Authors:	Toigo, A. D.; Richardson, M. I.
Journal:	The Fifth International Conference on Mars, July 19-24, 1999, Pasadena, California, abstract no. 6233
Publication Date:	Jul 1999
Origin:	LPI
Bibliographic Code:	1999ficm.conf.6233T
Abstract:	Not Available

Title:	The Water Cycle: Dynamics of Reservoir Exchange, Transport, and Integrated Behaviour
Authors:	Richardson, M. I.
Journal:	The Fifth International Conference on Mars, July 19-24, 1999, Pasadena, California, abstract no. 6021
Publication Date:	Jul 1999
Origin:	LPI
Bibliographic Code:	1999ficm.conf.6021R
Abstract:	Not Available

Title:	Viking Infrared Measurements of Martian Atmospheric Temperatures Revisited
Authors:	Wilson, R. J.; Richardson, M. I.
Affiliation:	AA(NOAA/GFDL), AB(UCLA)
Journal:	American Astronomical Society, DPS meeting #30, #04.05; Bulletin of the American Astronomical Society, Vol. 30, p.1021
Publication Date:	Sep 1998
Origin:	AAS
Abstract Copyright:	(c) 1998: American Astronomical Society
Bibliographic Code:	1998DPS....30.0405W
Abstract:	Viking Infrared Thermal Mapper (IRTM) data provide the foundation for much of our current knowledge of the present Martian climate. The IRTM data, which were collected over a period in excess of two Mars years, contain a wealth of information on the spatial and temporal variation of surface and atmospheric temperatures on diurnal to seasonal time scales. The 15 micron channel is of particular interest for atmospheric studies as it was designed to measure brightness temperatures (T15) within a deep layer of atmosphere centered at roughly 0.5 mb ( 25 km). Our re-examination of the T15 data suggests that the 15 micron channel was sensitive to surface radiance to an extent that the air temperature measurements are significantly biased. This bias is suggested by the strong correlation between the diurnal variation of tropical surface and T15 temperatures (for non-dust storm conditions). Atmospheric thermal tide modeling provides a basis for distinguishing between the surface and atmospheric contributions to the T15 observations. We use this approach to estimate the surface radiance contribution, which may then be removed from the T15 signal, allowing the atmospheric temperature signal to be recovered. We propose that midday, tropical T15 temperatures 'corrected' in this manner are over 15 K cooler than the IRTM observations. This suggestion is supported by a comparison of IRTM data with Mariner 9 IRIS data. Further, 'correcting' global average IRTM temperatures accounts for the instrumental bias found to exist between simultaneous IRTM and microwave observations. We will present a description of the revised T15 temperatures and discuss aspects of the martian circulation and climate which are highlighted by a consideration of the reprocessed observations.

Title:	Mars GCM Experiments: Application to the Transport and Behaviour of Water
Authors:	Richardson, M. I.; Wilson, R. J.; Paige, D. A.; Wood, S. E.
Affiliation:	AA(UCLA), AB(GFDL), AC(UCLA), AD(UCLA)
Journal:	American Astronomical Society, DPS meeting #29, #06.03; Bulletin of the American Astronomical Society, Vol. 29, p.967
Publication Date:	Jul 1997
Origin:	AAS
Abstract Copyright:	(c) 1997: American Astronomical Society
Bibliographic Code:	1997DPS....29.0603R
Abstract:	The Martian water cycle is highly asymmetric with regard to season. Spacecraft and telescopic observations show peak column water vapour abundances over the northern summer high latitudes ( ~ 90prmu m) with the southern summer peak being smaller ( ~ 20prmu m) and appearing further from the pole. This distribution of vapour results in an annual average meridional vapour gradient whose means of maintenance has yet to be conclusively determined (Jakosky and Haberle, 1992). Hypotheses thus advanced include a net annual transfer of water from north to south, more vigorous meridional transport during southern summer (Davies 1981, James 1985), and trapping of vapour in the northern summer hemisphere by the circulation (Haberle and Jakosky 1990), water condensation (Clancy {et} {al.} 1996), or subsurface adsorption (Houben {et} {al.} 1997). The GFDL Mars General Circulation Model (Wilson and Hamilton 1996 and Wilson {et} {al.} 1997, this volume) has been augmented with water processes including: atmospheric water vapour transport, water exchange with surface ice, atmospheric vapour condensation, and subsurface water exchange. This model represents the first treatment of the water cycle in a full General Circulation Model including the effects of topography, diurnal cycle, and interactive atmospheric dust. Results will be shown from model experiments designed to assess the ability of the atmosphere to extract water from the north polar cap source and effect equatorward transport. The role of atmospheric vapour condensation in limiting the transport of water, its effect on the spatial distribution of dust (via the use of dust for water condensation nuclei), and consequently its influence on the vigour of circulation (by altering the amount of solar radiation absorbed by airborne dust) will be examined.

Title:	Simulation of Aerosol and Water Vapor Transport with the GFDL Mars General Circulation Model.
Authors:	Wilson, R. J.; Richardson, M. I.; Clancy, R. T.; Rodin, A. V.
Affiliation:	AA(GFDL/NOAA), AB(UCLA), AC(SSI, Boulder), AD(IKI, Moscow)
Journal:	American Astronomical Society, DPS meeting #29, #06.02; Bulletin of the American Astronomical Society, Vol. 29, p.966
Publication Date:	Jul 1997
Origin:	AAS
Abstract Copyright:	(c) 1997: American Astronomical Society
Bibliographic Code:	1997DPS....29.0602W
Abstract:	Observations of the martian atmosphere reveal a strong annual modulation of atmospheric temperature that is evidently due to the pronounced seasonal asymmetry in solar radiation and the highly variable distribution of aerosol. The implied variations in thermal forcing are closely coupled to the character and vigor of the atmospheric general circulation through the raising and transport dust. The GFDL Mars GCM has been developed to investigate the interaction between thermal forcing and the atmospheric circulation, most notably the Hadley circulation and the thermal tides (Wilson and Hamilton, 1996). Using a prescribed aerosol source in the bottom atmospheric layer, the model self-consistently calculates aerosol transport and radiative heating. For example, with a sufficiently rapid injection of aerosol into the atmosphere, a realistic simulation of the 1977b global dust storm and associated winter polar warming may be obtained (Wilson, 1997). Sources and sinks of water vapor and condensate and their transport have also been incorporated in the GCM in order to explore arguments (Clancy et al. 1996) that the water vapor distribution may play a role in establishing and maintaining a relatively clear and cold atmosphere during the Northern hemisphere summer season. Simulations indicate that inclusion of possible radiative and sedimentation effects of water-ice-coated dust can have a significant interactive effect on the aerosol and temperature distribution in the martian tropical region. We will present results for a variety of dust source scenarios which illustrate the role of aerosol in the martian climate.

Title:	Atmospheric Heat, Dust, and Water Transport During Martian Polar Warmings
Authors:	Richardson, M. I.; Murphy, J. R.; Haberle, R. M.; Paige, D. A.; Schaeffer, J.
Affiliation:	AA(UCLA), AB(San Jose State), AC(NASA/Ames), AD(UCLA), AE(Sterling Software)
Journal:	American Astronomical Society, DPS meeting #28, #03.12; Bulletin of the American Astronomical Society, Vol. 28, p.1066
Publication Date:	Sep 1996
Origin:	AAS
Abstract Copyright:	(c) 1996: American Astronomical Society
Bibliographic Code:	1996DPS....28.0312R
Abstract:	How the Martian atmosphere transports heat, dust, and water into the polar air column is likely to affect the development of the polar layered terrains, growth of the seasonal polar caps, optical properties of the polar caps, and partitioning of CO2 condensation between the atmosphere and surface. It has been known for some time that the vigour of the large scale circulation and transport into the polar air mass are related to the amount of dust suspended in the atmosphere. During periods of low dust loading, the Hadley circulation terminates well short of the polar regions and a strong, isolating polar jet vortex develops along the polar front. When dust increases, the Hadley cell expands and eddy transports increase. However, until recently it has not proven possible to simulate the most dramatic episode in observed polar meteorology: the polar warming following the second global dust storm of 1977. Model improvements have now allowed simulation of this event in the NASA Ames GCM (Haberle et al. 1996 - companion abstract). The ability of the Ames GCM to emulate the observed polar warming increases confidence in the fidelity of the model during periods of high dust loading. We will present analysis of model output for varying dust loading configurations. In particular we will illustrate variations in the heat transport associated with the mean circulation, and stationary and transient eddies; variations in the amount and location of atmospheric condensation; and the results of tracer transport studies using an aerosol model coupled to the GCM. We will also examine the simulated 1977 polar warming in order to compare with the Viking observations of atmospheric temperature and dust transport.

Title:	A Microphysical Model of CO_2 Snow on Mars
Authors:	Wood, S. E.; Richardson, M. I.; Paige, D. A.
Affiliation:	AA(UCLA), AB(UCLA), AC(UCLA)
Journal:	American Astronomical Society, DPS meeting #28, #03.05; Bulletin of the American Astronomical Society, Vol. 28, p.1065
Publication Date:	Sep 1996
Origin:	AAS
Abstract Copyright:	(c) 1996: American Astronomical Society
Bibliographic Code:	1996DPS....28.0305W
Abstract:	Atmospheric condensation of CO_2 is a critical but poorly understood part of the Martian seasonal CO_2 cycle. During polar night, the latent heat released by CO_2 condensation is the major heat source, and CO2 clouds can substantially reduce the infrared emission from the condensing seasonal CO_2 polar cap. The CO_2 snow which precipitates from the atmosphere may also help determine the radiative and physical characteristics of the seasonal CO_2 polar caps, depending on the relative amount of condensation which takes place in the atmosphere. Previous models of atmospheric CO_2 condensation on Mars have not taken into account the finite rates of nucleation, growth, and sedimentation, or the radiative effects of the CO_2 clouds themselves, and their results may be inconsistent with available data. In order to address these issues, we have developed a one-dimensional model of the growth and precipitation of CO_2 snow in the polar night atmosphere of Mars. The model includes a realistic treatment of the microphysical processes of heat and mass transfer in both the continuum and free molecular regimes, as well as the transition region. We have also taken into account surface kinetics, or the finite rate at which molecules can be incorporated into the crystal lattice. We will present model calculations of snow particle growth and sedimentation rates for different values of atmospheric supersaturation and nucleation height. These results are compared with Viking IRTM observations to place constraints on the amount of atmospheric condensation. We will also present predictions of what TES and MOLA will see on Mars Global Surveyor.

Title:	Microphysical and Radiative Processes in CO2 Snow on Mars
Authors:	Wood, S. E.; Richardson, M. I.; Paige, D. A.
Journal:	American Astronomical Society, DPS Meeting #27, #15.07; Bulletin of the American Astronomical Society, Vol. 27, p.1098
Publication Date:	Jun 1995
Origin:	ADS
Bibliographic Code:	1995DPS....27.1507W
Abstract:	Not Available

Title:	Mars Winter Polar Vortices: Inter-Hemispheric Asymmetry in Tracer and Heat Transport
Authors:	Richardson, M. I.; Paige, D. A.; Zurek, R. W.; Murphy, J. R.; Haberle, R. M.
Journal:	American Astronomical Society, DPS Meeting #27, #04.03; Bulletin of the American Astronomical Society, Vol. 27, p.1065
Publication Date:	Jun 1995
Origin:	ADS
Bibliographic Code:	1995DPS....27.0403R
Abstract:	Not Available

Title:	IRTM brightness temperature maps of the Martian south polar region during the polar night: The cold spots don't move
Authors:	Paige, D. A.; Crisp, D.; Santee, M. L.; Richardson, M. I.
Affiliation:	AA(California Univ., Los Angeles.), AB(California Univ., Los Angeles.), AC(California Univ., Los Angeles.), AD(California Univ., Los Angeles.)
Journal:	In Lunar and Planetary Inst., Mars: Past, Present, and Future. Results from the MSATT Program, Part 1 p 34-35 (SEE N94-33190 09-91)
Publication Date:	n/a 1993
Origin:	STI
Keywords:	BRIGHTNESS TEMPERATURE, MARS SURFACE, PLANETARY TEMPERATURE, POLAR REGIONS, TEMPERATURE DISTRIBUTION, THERMAL MAPPING, MARS ATMOSPHERE, NIGHT, POLAR CAPS, VIKING 2 SPACECRAFT
Bibliographic Code:	1993mppf.proc...34P
Abstract:	A series of infrared thermal mapper (IRTM) south polar brightness temperature maps obtained by Viking Orbiter 2 during a 35-day period during the southern fall season in 1978 was examined. The maps show a number of phenomena that have been identified in previous studies, including day to day brightness temperature variations in individual low temperature regions and the tendency for IRTM 11-micron channel brightness temperatures to also decrease in regions where low 20-micron channel brightness temperatures are observed. The maps also show new phenomena, the most striking of which is a clear tendency for the low brightness temperature regions to occur at fixed geographic regions. During this season, the coldest low brightness temperatures appear to be concentrated in distinct regions, with spatial scales ranging from 50 to 300 km. There are approximately a dozen of these concentrations, with the largest centered near the location of the south residual polar cap. Other concentrations are located at Cavi Angusti and close to the craters Main, South, Lau, and Dana. Broader, less intense regions appear to be well correlated with the boundaries of the south polar layered deposits and the Mountains of Mitchell. No evidence for horizontal motion of any of these regions has been detected.

Title:	New dust opacity maps from Viking IR thermal mapper data
Authors:	Martin, T. Z.; Richardson, M. I.
Affiliation:	AA(Imperial Coll. of Science and Technology, London, England), AB(Imperial Coll. of Science and Technology, London, England)
Journal:	In Lunar and Planetary Inst., Workshop on the Martian Surface and Atmosphere Through Time p 101-102 (SEE N92-28988 19-91)
Publication Date:	Dec 1992
Origin:	STI
Keywords:	DUST STORMS, MARS ATMOSPHERE, MARS SURFACE, THERMAL MAPPING, RADIATION ABSORPTION, VIKING MARS PROGRAM
Bibliographic Code:	1992msat.work..101M
Abstract:	Mapping of dust opacity of the Martian atmosphere, using the silicate-induced absorption of 9 micron radiation, was performed with the Viking Infrared Thermal Mapper (IRTM) data for several local dust storms and in a global sense. We present here the first results from an effort to extend the earlier mapping work to the period of the 1977b major storm, and to concentrate attention on the details of opacity behavior during the initial phases of the 1977a and b storms.

Title:	Global Behavior of Martian Atmospheric Dust During the Viking ERA
Authors:	Martin, T. Z.; Richardson, M. I.
Journal:	Abstracts of the Lunar and Planetary Science Conference, volume 23, page 847, (1992)
Publication Date:	Mar 1992
Origin:	METBASE
Bibliographic Code:	1992LPI....23..847M
Abstract:	Not Available