Aeolis Research | Abstracts 2004

Abstracts 2004

2005

Title:	Simulating Titan's Atmosphere With the Titan WRF General Circulation Model
Authors:	Newman, C. E.; Richardson, M. I.; Toigo, A. D.; Inada, A.
Affiliation:	AA(California Institute of Technology, MC 150-21, GPS, Caltech, 1200 E. California Boulevard, Pasadena, CA 91125 United States ; claire@gps.caltech.edu), AB(California Institute of Technology, MC 150-21, GPS, Caltech, 1200 E. California Boulevard, Pasadena, CA 91125 United States ; mir@gps.caltech.edu), AC(Kobe University, Graduate School of Science and Technology, Kobe University, Rokkodai-cho 1-1, Nada-ku, Kobe, 657-8501 Japan ; toigo@astro.cornell.edu), AD(California Institute of Technology, MC 150-21, GPS, Caltech, 1200 E. California Boulevard, Pasadena, CA 91125 United States ; inada@gps.caltech.edu)
Journal:	American Geophysical Union, Fall Meeting 2005, abstract #P43B-05
Publication Date:	Dec 2005
Origin:	AGU
Keywords:	0343 Planetary atmospheres (5210, 5405, 5704), 3346 Planetary meteorology (5445, 5739), 5405 Atmospheres (0343, 1060), 6281 Titan
Abstract Copyright:	(c) 2005: American Geophysical Union
Bibliographic Code:	2005AGUFM.P43B..05N
Abstract:	Titan WRF is a new three-dimensional model for the atmosphere of Titan, and is a globalized, `Titan'-ified version of the Earth-based, mesoscale `Weather Research and Forecasting' model. Titan WRF thus inherits all of the desirable features from the original model, including highly parallelized and accurate code (ideal for the long simulations required here) and the ability to place high resolution nests within lower resolution domains (thus study certain areas in high detail without the expense of running the entire model at this resolution). Unlike the original mesoscale version of WRF, however, Titan WRF does not require forcing from a separate model. Our eventual aim is to use Titan WRF to study the onset and evolution of methane clouds in Titan's atmosphere, although initially we are concerned with producing and validating the modeled atmosphere and its seasonal changes, first with a constant haze distribution (varying with height only) then with advection of radiatively-active haze within the atmosphere. We will present the first results for each season of a Titan year, as simulated by Titan WRF (with a constant haze distribution) following several years during which the model atmosphere is allowed to `spin up' due to contact and exchange of angular momentum with the surface. These results will include zonal mean winds (including a discussion of the amount of equatorial superrotation produced), temperatures and mass streamfunctions for different seasons. We will compare these with available observations, then discuss our future plans.

Title:	Three-Dimensional Climate Modeling of the Amazonian Environment and Glaciation
Authors:	Richardson, M. I.; Mischna, M. A.
Affiliation:	AA(California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States ; mir@gps.caltech.edu), AB(Jet Propulsion Laboratory, 4800 Oak Grove Dr, Pasadena, CA 91109 United States ; michael.a.mischna@jpl.nasa.gov)
Journal:	American Geophysical Union, Fall Meeting 2005, abstract #P34A-07
Publication Date:	Dec 2005
Origin:	AGU
Keywords:	4946 Milankovitch theory, 5405 Atmospheres (0343, 1060), 5416 Glaciation, 5462 Polar regions, 6225 Mars
Abstract Copyright:	(c) 2005: American Geophysical Union
Bibliographic Code:	2005AGUFM.P34A..07R
Abstract:	Spacecraft data increasingly suggest that Mars has experienced dramatic changes in the distribution of surface and subsurface water ice in the recent past, potentially associated with rather different climate states. In the limit of high obliquity, this likely corresponds to tropical water ice sheets, while in the low obliquity limit, it corresponds to atmospheric collapse. Climate models suggest that such changes in the planetary environment and water distribution are expected on the basis of the large change in planetary orbital parameters on time scales >10{5} yrs. These variations are quazi-cyclical, and so are expected to have caused ongoing (non-secular) changes in climate throughout the Amazonian. Indeed, some orbital forcing of climate may be involved in the episodes of raised and lowered water table in Terra Meridiani, as inferred from Opportunity observations. It is believed that superposed on this quazi-cyclical pattern is a signal of net atmospheric deflation, due primarily to loss to space. The challenge for climate dynamics is to explain the nature and extent of climate change through time, with a particular focus on the changing distribution and stability of water. This presentation will review developments to date, model sensitivities, and future directions.

Title:	Orbitally-Driven Change in the Martian Atmosphere
Authors:	Mischna, M. A.; Richardson, M. I.; Newman, C. E.; Toigo, A. D.; Vasavada, A. R.; Inada, A.
Affiliation:	AA(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 United States ; michael.a.mischna@jpl.nasa.gov), AB(California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States ; mir@gps.caltech.edu), AC(California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States ; claire@gps.caltech.edu), AD(Graduate School of Science and Technology, Kobe University, 1-1 Rokkodai-cho, Nada Kobe, 657-8501 Japan ; toigo@astro.cornell.edu), AE(Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 United States ; ashwin.r.vasavada@jpl.nasa.gov), AF(California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States ; inada@gps.caltech.edu)
Journal:	American Geophysical Union, Fall Meeting 2005, abstract #P31B-0202
Publication Date:	Dec 2005
Origin:	AGU
Keywords:	0343 Planetary atmospheres (5210, 5405, 5704), 5405 Atmospheres (0343, 1060), 5422 Ices, 5445 Meteorology (3346), 6225 Mars
Abstract Copyright:	(c) 2005: American Geophysical Union
Bibliographic Code:	2005AGUFM.P31B0202M
Abstract:	We consider the impact of orbital cycling (obliquity, eccentricity, perihelion precession) on the martian atmospheric water cycle through recent Amazonian history. Changes in obliquity from present-day values can have a significant effect on the abundance of water vapor in the martian atmosphere. In addition, the magnitude and distribution of surface water ice deposits can vary significantly, on timescales commensurate with the period of obliquity oscillation (100 ky). We have used results from both the GFDL Mars GCM as well as the Planetary WRF GCM to examine possible changes in the water cycle induced by these orbital motions. Preliminary results indicate that if a sublimation lag develops over extant polar deposits during an extended rise to high obliquity (105-106 yr), the amount of water vapor released into the atmosphere will be correspondingly and significantly reduced, maintained in balance with any ice deposits that developed in the lower latitudes prior to the ``shutting off'' of the polar ice deposits. Under these conditions, annual average water abundances at high obliquity may only be 20-80 prμm, one to two orders of magnitude less than previous estimates, and only a factor of a few higher than present-day values. Further, the ``wettest'' periods in recent Mars history may not be directly correlated with the highest mean obliquity but rather with brief periods of high obliquity when the mean obliquity was only slightly higher than present.

Title:	Simulation of Water Cycle With a Martian Weather Research and Forecast Model
Authors:	Inada, A.; Richardson, M. I.; Mischna, M. A.; Newman, C. E.; Toigo, A. D.; Vasavada, A. R.
Affiliation:	AA(California Institute of Technology, M.S. 150-21 1200 E. California Blvd., Pasadena, CA 91125 United States ; inada@gps.caltech.edu), AB(California Institute of Technology, M.S. 150-21 1200 E. California Blvd., Pasadena, CA 91125 United States ; mir@gps.caltech.edu), AC(Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States ; mischna@mail.jpl.nasa.gov), AD(California Institute of Technology, M.S. 150-21 1200 E. California Blvd., Pasadena, CA 91125 United States ; claire@gps.caltech.edu), AE(Graduate School of Science and Technology, Kobe Univ., 1-1 Nada, Kobe, 657-8501 Japan ; toigo@astro.cornell.edu), AF(Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States ; ashwin_vasavada@yahoo.com)
Journal:	American Geophysical Union, Fall Meeting 2005, abstract #P21E-08
Publication Date:	Dec 2005
Origin:	AGU
Keywords:	5210 Planetary atmospheres, clouds, and hazes (0343), 6225 Mars
Abstract Copyright:	(c) 2005: American Geophysical Union
Bibliographic Code:	2005AGUFM.P21E..08I
Abstract:	The water cycle in the Martian atmosphere is influenced by exchange with the subsurface, condensation on the surface, mixing between the boundary layer and the free atmosphere, large-scale horizontal mixing of air masses and precipitation as water ice particles. We have installed a water cycle model with microphysics processes into the Martian Weather Research and Forecast (WRF) model. It treats subsurface water diffusion and adsorptive / condensational exchange, surface ice formation and diffusive mixing in the atmosphere. Formed water ice particles in the atmosphere are transformed by advection, diffusion and sedimentation. We will present the spatial and diurnal variation of water including cloud/fog formation.

Title:	THEMIS-VIS Measurements of the Altitude and Velocity of Clouds in the Martian Mesosphere
Authors:	McConnochie, T. H.; Bell, J. F.; Savransky, D.; Wolff, M. J.; Christensen, P. R.; Richardson, M. I.; Titus, T. N.
Affiliation:	AA(Cornell University, Space Sciences Building, Ithaca, NY 14853 United States ; thm9@cornell.edu), AB(Cornell University, Space Sciences Building, Ithaca, NY 14853 United States ; jfb8@cornell.edu), AC(Cornell University, Space Sciences Building, Ithaca, NY 14853 United States ; ds264@cornell.edu), AD(Space Science Institude, 4750 Walnut Street Suite 205, Boulder, CO 80301 United States ; wolff@spacescience.org), AE(Arizona State University, Mars Space Flight Facility, Tempe, AZ 85287 United States ; phil.christensen@asu.edu), AF(Caltech, Div Geological & Planetary Sci MC 150-21, Pasadena, CA 91125 United States ; mir@gps.caltech.edu), AG(USGS, 2255 North Gemini Drive, Flagstaff, AZ 86001 United States ; ttitus@usgs.gov)
Journal:	American Geophysical Union, Fall Meeting 2005, abstract #P21E-03
Publication Date:	Dec 2005
Origin:	AGU
Keywords:	5405 Atmospheres (0343, 1060), 5464 Remote sensing, 5494 Instruments and techniques
Abstract Copyright:	(c) 2005: American Geophysical Union
Bibliographic Code:	2005AGUFM.P21E..03M
Abstract:	Although Mars Odyssey's Thermal Emission Imaging System visible subsystem (THEMIS-VIS) was not designed or intended for stereo imaging or cloud tracking, its multiple exposure color-imaging sequence serendipitously causes a parallax effect that allows the height of high-altitude clouds to be determined, and has sufficient time delay to detect the movement of these clouds. As a result, THEMIS-VIS has acquired exceptionally high resolution (36 or 72 m pixel scale) nadir-pointed images of martian clouds with altitudes in the 60-80 km altitude range, and is providing the first direct measurements of wind speed at these altitudes. We discover high altitude cloud candidates by noticing a severe misalignment of cloud features between any two bands of an image which has been map-projected at the altitude of the local surface. In order to measure altitude and velocity, we reproject the subframes that make up a THEMIS-VIS image at a series altitudes above the local surface, shifting the subframes relative to each other to account for a range of candidate velocities. To select the best fitting altitude and velocity, we manually inspect the reprojected images to find an approximate solution, and then maximize the correlation between the 425 nm band and 540 nm band within a manually selected high-constrast cloud-dominated region of the image in order to refine the solution. The precision of this technique is of course inherently limited by the sharpness of the cloud features. To date we have obtained two high-altitude velocity measurements, and have identified 50 more images with high altitude clouds that are likely to yield velocity measurements. In THEMIS sequence number V06930045, 217 degrees L_s and 47 degrees north latitude, we measure eastward cloud motion of 60 +/- 15 m/s at an altitude of 70 +/- 5 km. In THEMIS sequence number V10526009, 26 degrees L_s and 0.5 degrees north latitude, we measure westward cloud motion of 90 +/- 20 m/s at an altitude of 80 +/- 5 km.

Title:	Planetary WRF: a Multi-Scale, Planetary, Atmospheric Model
Authors:	Toigo, A.; Richardson, M. I.; Newman, C. E.
Affiliation:	AA(Kobe University, Graduate School of Science and Technology Rokkodai-cho 1-1, Nada-ku, Kobe, 657-8501 Japan ; toigo@astro.cornell.edu), AB(California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States ; mir@gps.caltech.edu), AC(California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States ; claire@gps.caltech.edu)
Journal:	American Geophysical Union, Fall Meeting 2005, abstract #P13A-0140
Publication Date:	Dec 2005
Origin:	AGU
Keywords:	3337 Global climate models (1626, 4928), 3346 Planetary meteorology (5445, 5739), 5405 Atmospheres (0343, 1060), 5445 Meteorology (3346), 6225 Mars
Abstract Copyright:	(c) 2005: American Geophysical Union
Bibliographic Code:	2005AGUFM.P13A0140T
Abstract:	The NCAR terrestrial Weather Research and Forecast (WRF) atmospheric model has been converted into a global, planetary model. Planetary WRF is the first truly multi-scale numerical model having the ability to run on scales from meters to global, and with 2-way domain nesting interactivity. The model is fully compressible, has 3D Coriolis and curvature treatment and has hydrostatic and non-hydrostatic options. The model has initially been converted for use on Mars and Titan with future applications to other planets planned. The dynamical core has been validated using the standardized forcing and setup described in Held and Suarez (1994), and comparison of 1D and 3D Martian and 1D Titan versions with existing models. The conversion process and preliminary results at a variety of scales including validation will be presented.

Title:	A New General Circulation Model of Titan's Atmosphere
Authors:	Newman, C. E.; Richardson, M. I.; Toigo, A. D.
Affiliation:	AA(California Institute of Technology), AB(California Institute of Technology), AC(Kobe University)
Journal:	American Astronomical Society, DPS meeting #37, #51.10; Bulletin of the American Astronomical Society, Vol. 37, p.735
Publication Date:	Aug 2005
Origin:	AAS
Bibliographic Code:	2005DPS....37.5110N
Abstract:	Some big questions relating to Titan's atmosphere are: How much equatorial superrotation occurs? What determines the way in which albedo patterns change over time at different wavelengths? and What determines the size, frequency and location of the recently observed southern hemisphere clouds? To investigate such questions properly requires a three-dimensional model of Titan's thick atmosphere, which can examine different scenarios in multi-year simulations. Such simulations are computationally demanding due to Titan's long radiative and seasonal timescales, as well as its slow rotation rate, all of which mean a long time is required to spin up then conduct each run. This demands the use of an efficient, accurate, and mass- and momentum-conserving model. One such model is the newly developed Planetary Weather Research and Forecasting model (PWRF), which is based on a pre-existing terrestrial mesoscale model (WRF). WRF is a highly parallelized and numerically efficient model, which is also able to place high resolution 'nests' (with information passing both inwards and outwards) over selected regions where resolving small-scale features is most necessary. This is very useful, as increasing the resolution everywhere would slow the model considerably. PWRF retains these features, but extends to using a global mother domain (no separate global model required), and has also been adapted to include a planetary timing system (using areocentric longitude) and other planetary options (such as radiation schemes). We will present results from the Titan version of PWRF to demonstrate how well the model reproduces key aspects of Titan's circulation (e.g. superrotation, temperature structure). We will describe our plans to include aerosol transport, and our eventual aim to model the recently observed (telescopically from Earth, e.g. Griffith et al. Nature 1998, Brown et al. Nature 2002, and from Cassini, e.g. Porco et al. Nature 2005) methane clouds. This work is funded by NASA.

Title:	Simulation of Column Water Processes with a One Dimensional Martian Climate Model
Authors:	Inada, A.; Richardson, M. I.; Mischna, M. A.; Newman, C. E.; Toigo, A. D.; Vasavada, A. R.
Affiliation:	AA(California Institute of Technology), AB(California Institute of Technology), AC(Jet Propulsion Laboratory), AD(California Institute of Technology), AE(Graduate School of Science and Technology, Kobe Univ.), AF(Jet Propulsion Laboratory)
Journal:	American Astronomical Society, DPS meeting #37, #33.22; Bulletin of the American Astronomical Society, Vol. 37, p.696
Publication Date:	Aug 2005
Origin:	AAS
Bibliographic Code:	2005DPS....37.3322I
Abstract:	The variation of water vapour near the Martian surface will be influenced by exchange with the subsurface, condensation on the surface and in the atmosphere, mixing between the boundary layer and the free atmosphere, and the large-scale horizontal mixing of air masses. In order to isolate column processes from those of transport, we have developed a "complete" model of column water cycling based around a one-dimensional version of the Martian Weather Research and Forecast (WRF) model. Explicitly treated processes include subsurface water diffusion and adsorptive/condensational exchange, surface ice formation, diffusive mixing in the atmosphere, and the microphysics of atmospheric cloud/fog formation and sedimentation. The formation of surface ices and clouds/fogs allow for the activation of feedback systems due to their influence on the radiative heating of the surface and hence the surface energy balance and temperature. The model is used to assess the variation of cloud/fog vertical structure and water vapour at likely Phoenix and MSL landing sites (for which fog and water vapour measurements, respectively, are planned for collection). The implication of cloud radiative effects for retrieval of surface thermal properties will also be discussed.

Title:	Development of a Martian Sonic Anemometer
Authors:	Dissly, R. W.; Banfield, D. J.; Lasnik, J.; Waters, J. T.; McEwan, I. J.; Richardson, M. I.
Affiliation:	AA(Ball Aerospace), AB(Cornell), AC(Ball Aerospace), AD(Cornell), AE(Caltech), AF(Caltech)
Journal:	American Astronomical Society, DPS meeting #37, #18.05; Bulletin of the American Astronomical Society, Vol. 37, p.650
Publication Date:	Aug 2005
Origin:	AAS
Bibliographic Code:	2005DPS....37.1805D
Abstract:	This presentation will describe the progress to-date on the development of an acoustic anemometer for the in-situ measurement of wind speeds on Mars, funded by NASA PIDDP. Improved measurements of Martian winds are needed for several reasons: better prediction and understanding of global and regional weather, direct measurement of fluxes between surface/atmosphere of momentum, heat, and trace atmospheric constituents, characterizing and monitoring boundary layer winds that influence the safe delivery of spacecraft to/from the Martian surface, and improved characterization of geologically important aeolian processes that can pose a hazard to future exploration via dust storms and dust devils. Prior attempts to measure surface winds have been limited in capability and difficult to calibrate. Sonic anemometry, measuring wind speed via sound pulse travel-time differences, can overcome many of these issues. Sonic anemometry has several distinct advantages over other methods such as hot wire techniques: higher sensitivity ( <5 cm/s), higher time resolution (10-100 Hz), and fewer intrinsic biases for improved accuracy. Together, these open the possibility of resolving turbulent boundary layer eddies to directly capture surface-to-atmospheric fluxes for the first time. We will describe the results of our development of an acoustic anemometer using capacitive micro-machined devices, optimized for acoustic coupling in a low-pressure medium like the Martian atmosphere. This development includes transducer characterization tests in a pressure chamber at Ball Aerospace with Mars-relevant CO2 pressures. We will also describe experimental results showing that the addition of water in a low-pressure CO2 atmosphere can significantly increase acoustic attenuation. Finally we will describe plans for further optimization of the instrument for future Mars payloads.

Title:	Surface Dust Redistribution on Mars as Observed by the Mars Global Surveyor
Authors:	Szwast, M. A.; Richardson, M. I.; Vasavada, A. R.
Journal:	36th Annual Lunar and Planetary Science Conference, March 14-18, 2005, in League City, Texas, abstract no.2191
Publication Date:	Mar 2005
Origin:	LPI
Bibliographic Code:	2005LPI....36.2191S
Abstract:	A study of MGS TES albedo data set as a proxy for dust cover was performed focusing around the 2001 global dust storm. We found widespread surface dust redistribution caused by the storm, and recovery since implying a multi-year cyclical nature.

Title:	GCM Simulations of the Tropical Hydrogen Distribution Observed by Mars Odyssey
Authors:	Mischna, M. A.; Richardson, M. I.
Journal:	36th Annual Lunar and Planetary Science Conference, March 14-18, 2005, in League City, Texas, abstract no.1518
Publication Date:	Mar 2005
Origin:	LPI
Bibliographic Code:	2005LPI....36.1518M
Abstract:	We use the GFDL Mars GCM with a fully coupled atmosphere-regolith water cycle to understand the age of the hydrogen deposits observed by Mars Odyssey. Trends in subsurface ice evolution are observed during various obliquity and polar cap conditions.

2004

Title:	Does the present-day wind regime explain the location and geomorphology of dunes in the southern highlands of Mars?
Authors:	Fenton, L. K.; Toigo, A. D.; Richardson, M. I.
Affiliation:	AA(Arizona State University, Department of Geology, MS 6305, Tempe, AZ 85287 United States ; lkfenton@asu.edu), AB(Cornell University, Center for Radiophysics and Space Research, 326 Space Sciences Bldg., Ithaca, NY 14853 United States ; toigo@astro.cornell.edu), AC(Caltech, Division of Geological and Planetary Sciences, MS 150-21, Pasadena, CA 91125 United States ; mir@gps.caltech.edu)
Journal:	American Geophysical Union, Fall Meeting 2004, abstract #P22A-05
Publication Date:	Dec 2004
Origin:	AGU
Keywords:	5415 Erosion and weathering, 3329 Mesoscale meteorology, 3346 Planetary meteorology (5445, 5739), 3307 Boundary layer processes, 1625 Geomorphology and weathering (1824, 1886)
Bibliographic Code:	2004AGUFM.P22A..05F
Abstract:	Dozens of dunefields are scattered throughout the southern highlands of Mars, mostly (but not entirely) located in the floors of impact craters. MOC Narrow Angle images reveal that these dunes are not basic barchan or transverse in form, but rather that they are a combination of barchans, reversing, linear, and star dunes, indicating that they were formed in a multi-directional wind regime. In Noachis Terra, west of Hellas Planitia, almost all dunefields show three dominant slipface orientations, indicating formative winds from the SW, SE, and NE. Different dunefields show these three winds in different proportions, suggesting that in different areas, different winds have dominated. To determine how these different winds interact in the present day wind regime, we ran the Mars MM5 over Noachis Terra. The model runs include twelve 10-day runs spaced throughout the martian year, with a grid size of 20 km and a timestep of 10 seconds (physical parameters were saved once every hour). Winds from the SW blow during winter afternoons, caused by geostrophic forcing. Because of coverage from the seasonal polar cap, these winds are more effective in blowing sand at latitudes poleward of 50° S, roughly consistent with the observed spatial pattern in dune morphology. Winds from the SE blow during the early to mid afternoon in the spring, caused by slope winds blowing up and over the rim of the Hellas basin. These winds should be more common closer to Hellas Planitia, but they appear in dunes throughout Noachis Terra. Winds from the NE blow in the evening during summer, and they are katabatic flows that accelerate into topographic lows, following the diurnal tide. These winds are strongest equatorward of 50° S, which is fairly consistent with observed dune morphology. Discrepancies between the model and observed dune slipfaces can be explain by shifting physical parameters (i.e., dust loading or obliquity).

Title:	Surface Dust Redistribution on Mars as Observed by the Viking and Mars Global Surveyor Orbiters
Authors:	Szwast, M.; Richardson, M. I.; Vasavada, A. R.; Wang, H.
Affiliation:	AA(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States ; ), AB(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States ; ), AC(Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States ; ), AD(Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 United States ; Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States ; )
Journal:	American Geophysical Union, Fall Meeting 2004, abstract #P22A-04
Publication Date:	Dec 2004
Origin:	AGU
Keywords:	5415 Erosion and weathering, 5445 Meteorology (3346), 5462 Polar regions, 5470 Surface materials and properties, 6225 Mars
Bibliographic Code:	2004AGUFM.P22A..04S
Abstract:	The global redistribution of dust by the atmosphere is geologically and climatologically important. Dust deposition and removal at the surface represents ongoing sedimentary geology: a vestige of aeolian processes responsible for the concentration of vast dustsheets and potentially for ancient layered units at various locations on Mars. The varying amount of dust on the surface has also long been hypothesized as a factor in determining whether regional or global dust storms occur in a given year. Indeed, the atmosphere has a very short, sub-seasonal time-scale (or memory) and as such, any inter-annual variability in the climate system that is not simply ascribable to stochastic processes, must involve changing conditions on the surface. An excellent, multi-year dataset is provided by the combined Viking and Mars Global Surveyor (MGS) orbiter albedo and thermal observations, from the Infrared Thermal Mapper (IRTM) and Thermal Emission Spectrometer (TES), and from the MGS Mars Orbiter Camera Wide Angle imager (MOC-WA). This dataset allows investigation into the degree to which surface dust deposits on Mars really change: over decadal time scales, over the course of the annual cycle, and as a result of global and regional dust storms. The MGS mapping orbit data set extends over almost 3 Martian years at the time of writing, while the Viking data set provides a much less complete sampling of three northern summers/autumns and one southern summer/autumn. These data sets include three global dust storms (two for Viking and one for MGS) and smaller regional storms (one in the first TES mapping year and two in the third). We have examined the Viking IRTM, MGS TES, and MGS MOCWA data sets to determine what types of changes in dust coverage have occurred. Viking-to-MGS changes in albedo are highlighted by the drastic modification of a large, low albedo (low dust) feature to the east of Utopia Planitia. Year-to-year changes within the Viking and MGS records are dominanted by the effects of global dust storms. The 2001 storm observed by MGS is the best documented. We found a number of regions that changed significantly after the 2001 global dust storm. Areas with noticeable changes include the brightening of Syrtis Major, Hellas Planitia, and the region east of Hellas Planitia, and the darkening of Tharsis. Solis Planum, a region known to have participated as a secondary source for the 2001 storm became darker following the storm, while an area directly to the east of Solis became brighter. The majority of these changes are visible in both TES maps and MOC wide-angle images. These changes have been slowly relaxing back towards pre-storm conditions since the end of the storm. Similar albedo changes in these same regions were found associated with the global storms observed by the Viking IRTM. This suggests that the very limited number of dust storms observed by spacecraft have tended to produce the same kinds of changes in surface dust coverage. The origin of the long-term changes in Utopia are not understood.

Title:	The Long-Term Evolution of Transient Liquid Water on Mars
Authors:	Mischna, M. A.; Richardson, M. I.
Affiliation:	AA(Jet Propulsion Laboratory, 4800 Oak Grove Drive M/S 183-401, Pasadena, CA 91109 United States ; michael.a.mischna@jpl.nasa.gov), AB(California Institute of Technology, 1200 E. California Blvd. M/S 150-21, Pasadena, CA 91125 United States ; mir@gps.caltech.edu)
Journal:	American Geophysical Union, Fall Meeting 2004, abstract #P13A-0977
Publication Date:	Dec 2004
Origin:	AGU
Keywords:	5409 Atmospheres: structure and dynamics, 5445 Meteorology (3346), 5450 Orbital and rotational dynamics, 3344 Paleoclimatology, 3319 General circulation
Bibliographic Code:	2004AGUFM.P13A0977M
Abstract:	Liquid water is not currently stable on the surface of Mars but transient liquid water, generated by the melting of ice, may occur if surface temperatures are between the melting and boiling points and the surface pressure exceeds the triple point. Such conditions can be met on Mars with current-day surface pressures and obliquity due to the large diurnal range of surface temperatures, yielding the potential for liquid water. A general circulation model is used to undertake an initial exploration of the variation of this ``liquid water potential'' (LWP) for different obliquities and over a range of increased atmospheric CO2 abundances representing progressively earlier phases of Martian geological history. At higher obliquities and slightly higher surface pressures (<50 mb) possible in the relatively recent past (<108 yr), the LWP conditions are met over a very large fraction of the planet. However, as the surface pressure is increased above about 50--100 mb, the increased atmospheric heat capacity and greenhouse effect reduce the diurnal surface temperature range, resulting in daytime temperatures rarely exceeding the melting point. This reduction of peak daytime temperatures below the melting point greatly reduces the possibility of even transient liquid water. The modeling presented here does not extend to a state of stable liquid water for early Mars---how Mars may have yielded a ``warm, wet'' early climate is currently an open research question. However, if Mars had an early ``warm, wet'' stage, then the potential for liquid water on Mars has not decreased monotonically from that state to the present day, as the atmosphere was lost. Instead, a distinct minimum in LWP will have occurred during the extended period for which pressures were in the middle range of about 0.1 and 1 bar. These results suggest that the current climate and recent paleoclimate may be more conducive for liquid water than paleoclimate states corresponding to much thicker atmospheres. The existence of this ``dead zone'' for liquid water, likely extending over a large fraction of Martian history has direct and restrictive implications for chemical weathering and life. The fundamental conclusion of this study is insensitive to invocation of brines and to more detailed treatment of atmospheric radiative processes.

Title:	Variation of Non-Condensables in the Martian Atmosphere
Authors:	Xiao, 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 ; jiafang@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 2004, abstract #P11A-0962
Publication Date:	Dec 2004
Origin:	AGU
Keywords:	5405 Atmospheres: composition and chemistry, 5409 Atmospheres: structure and dynamics, 5462 Polar regions, 6225 Mars, 3319 General circulation
Bibliographic Code:	2004AGUFM.P11A0962X
Abstract:	The Martian atmosphere is dominated by CO{_2}, but a small fraction is made up of non-condensables, predominantly Ar and N{_2}. These non-condensables make up about 4.7% of the atmosphere, but this fraction is likely not constant over the seasonal cycle or spatially. The reason for this is that the major gas, CO{_2} condenses in the autumn pole and sublimes at the spring pole, concentrating and diluting, respectively, the non-condensable mass-mixing ratio. The purpose of this study has been to examine the seasonal cycle of non-condensables with a Martian General Circulation Model (GCM) to provide a basis of comparison with data becoming available from the Mars Odyssey spacecraft, and to provide insight into the evolving non-condensable distributions. The model includes a full seasonal cycle of CO{_2} and atmospheric dust.

Title:	Hydrodynamic Escape from Hydrogen Rich Atmospheres
Authors:	Parkinson, C. D.; Richardson, M. I.; Hill, D. J.
Affiliation:	AA(California Institute of Technology), AB(California Institute of Technology), AC(California Institute of Technology)
Journal:	American Astronomical Society, DPS meeting #36, #40.07; Bulletin of the American Astronomical Society, Vol. 36, p.1167
Publication Date:	Nov 2004
Origin:	AAS
Abstract Copyright:	(c) 2000: American Astronomical Society
Bibliographic Code:	2004DPS....36.4007P
Abstract:	Atmospheric loss processes have played a major role in the evolution and habitability of the terrestrial planet atmospheres in our solar system. The hydrogen escape rate to space is the key parameter that controls the composition of the primitive terrestrial atmosphere, including its possible methane concentration. Most models of the early atmosphere assume that hydrogen escapes at the diffusion-limited rate (Walker, 1977), but this need not necessarily have been true. A CO2- or CH4-rich primitive atmosphere may have been relatively cool in its upper regions, and the escape may therefore have been limited by energy considerations rather than by diffusion. Resolving questions of hydrogen escape for these cases requires solving a set of hydrodynamic equations for conservation of mass, momentum, and energy. Hydrodynamic escape may also be important for Close-in Extrasolar Gas Giants (CEGPs) such as HD209458b, which has recently been observed to be losing hydrogen by the Hubble Space Telescope (Vidal-Madjar et al., 2003; 2004). Although planetary hydrodynamic escape models have been created in the past (Watson et al., 1981; Kasting and Pollack, 1983; Chassefiere, 1996), the problems were solved by integrating the coupled, time independent mass, momentum, and energy equations for the escaping gas from the homopause out to infinity. Solving the one-dimensional, steady state approximation becomes problematic at the distance where the outflow becomes supersonic. A new technique has been developed for the treatment of hydrodynamic loss processes from planetary atmospheres that overcomes the instabilities inherent in modelling transonic conditions by solving the coupled, time dependent mass, momentum, and energy equations, instead of integrating time independent equations. We validate a preliminary model of hydrodynamic escape against simple, idealized cases (viz., steady state and isothermal conditions) showing that a robust solution obtains and then compare to existing cases in the literature as cited above. The general tools developed here are applied to the problems of hydrodynamic escape on the early Earth and close-in extrasolar gas giant planets and results from these analyses are shown.

Title:	The Martian Atmosphere, Climate, and General Circulation Models
Authors:	Richardson, M. I.
Affiliation:	AA(California Institute of Technology, MC 150-21, 1200 E. California Blvd., Pasadena, CA 91125 United States ; mir@gps.caltech.edu)
Journal:	American Geophysical Union, Spring Meeting 2004, abstract #SA51B-03
Publication Date:	May 2004
Origin:	AGU
Keywords:	0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707), 3367 Theoretical modeling, 5409 Atmospheres: structure and dynamics, 5445 Meteorology (3346), 6225 Mars
Bibliographic Code:	2004AGUSMSA51B..03R
Abstract:	Our understanding of the Martian atmosphere, and the embodiment of this understanding in GCM models, sits part way between that of the Earth's atmosphere and that of the other planets in the solar system. Compared to the Earth, it is incomplete even as it applies to certain basic, elementary components and it is studied by a very limited community. Compared to the other planets in the solar system, most elements of the circulation are understood in outline, the data sets are vast and rich, and a number of well-staffed, competing modeling groups exist. Given this ``middle sibling'' status of Martian atmospheric science, an obvious issue arises as to whom it should be compared: Is the paucity of our understanding compared to the Earth motivation for redoubled efforts, or advanced state of knowledge cause to refocus on other planetary bodies? In this presentation, I will review the components of the Martian circulation and the progress that has been made in their understanding through the synthesis of data with GCMs. I will also review the aspects of Martian climate that uniquely influence the atmosphere. These include the lofting of dust by large-scale winds and thermal convection, resulting in a permanent (if varying) dust haze that significantly increases atmospheric temperatures, and occasionally leading to the generation of global dust storms. The spontaneous generation of such storms in a GCM has only very recently been accomplished. The condensation of the major atmospheric constituent (CO2) onto the surface to form massive seasonal ice caps in the frigid polar winter also generates a significant climate signal and a pole-to-pole condensation flow. Finally, Mars possesses an active water cycle with the development of clouds, formation of seasonal water ice deposits, and storage of water in the near-sub surface as adsorbate. The water cycle is fundamentally driven by exchange with a residual water ice cap at the northern (and not the southern) pole. Such asymmetries abound in the Martian atmosphere and climate system - some are tied to the planetary eccentricity and some to the difference in topographic elevation of the two hemispheres. Many significant questions remain open regarding how these climate system elements interoperate and how they might have changed the face of Mars as forcing, due to abundance of greenhouse gases or the pattern of insolation associated with particular obliquity or orbital parameter values, have changed.

Title:	Interpreting Martian Paleoclimate with a Mars General Circulation Model
Authors:	Richardson, M. I.; Mischna, M. A.; Basu, S.; Fenton, L. K.; Wilson, R. J.
Journal:	35th Lunar and Planetary Science Conference, March 15-19, 2004, League City, Texas, abstract no.2100
Publication Date:	Mar 2004
Origin:	LPI
Bibliographic Code:	2004LPI....35.2100R
Abstract:	We review the capabilities and studies undertaken with the Geophysical Fluid Dynamics Laboratory (GFDL) Mars GCM.

Title:	Enhanced Water-Equivalent Hydrogen on the Western Flanks of the Tharsis Montes and Olympus Mons: Remnant Subsurface Ice or Hydrate Minerals?
Authors:	Elphic, R. C.; Feldman, W. C.; Prettyman, T. H.; Tokar, R. L.; Lanza, N.; Lawrence, D. J.; Head, J. W., III; Mischna, M. A.; Richardson, M. I.
Journal:	35th Lunar and Planetary Science Conference, March 15-19, 2004, League City, Texas, abstract no.2011
Publication Date:	Mar 2004
Origin:	LPI
Bibliographic Code:	2004LPI....35.2011E
Abstract:	Enhanced water-equivalent hydrogen (2 8 wt%) is found in and around the Tharsis Montes and Olympus Mons, especially on the western flanks. This is where glacial landforms are found, and where GCMs hint at past ice accumulations.

Title:	Explaining the Mid-Latitude Ice Deposits with a General Circulation Model
Authors:	Mischna, M. A.; Richardson, M. I.; Wilson, R. J.; Zent, A.
Journal:	35th Lunar and Planetary Science Conference, March 15-19, 2004, League City, Texas, abstract no.1861
Publication Date:	Mar 2004
Origin:	LPI
Bibliographic Code:	2004LPI....35.1861M
Abstract:	We look at the formation of the mid- and low-latitude subsurface water deposits using the GFDL Mars GCM with an active regolith. Results suggest such deposits are a combination of diffusively placed water and surface ice deposits while at high obliquity.

Title:	Dynamics and structure of the Mars atmosphere: The post-Viking perspective
Authors:	Zurek, R. W.; Murphy, J.; Kass, D.; Richardson, M. I.; Rafkin, S.; Malin, M.; Cantor, B.; Keating, G.; Smith, M.
Journal:	35th COSPAR Scientific Assembly. Held 18 - 25 July 2004, in Paris, France., p.4291
Publication Date:	n/a 2004
Origin:	ADS
Bibliographic Code:	2004cosp...35.4291Z
Abstract:	Past summaries of knowledge about the dynamics of the Mars atmosphere were based on Mariner 9 and Viking data and on then state-of-the-art general circulation models. Since then, Mars Pathfinder and the two Mars Exploration Rovers have provided new in situ entry data, and a suite of Mars spacecraft have provided in situ measurements during aerobraking and new remote sensing observations from orbit. Mars Express has joined the ongoing Mars Global Surveyor and the 2001 Mars Odyssey spacecraft in orbit around Mars, and the Mars Reconnaissance Orbiter is preparing for launch in 2005. Entry data and measurements from orbit are providing the data needed to test our understanding and our advanced modeling of Mars atmospheric processes. Analyses of these data have provided both confirmation of some earlier expectations and new perspectives on atmospheric dynamics. These will be reviewed in this talk, which will touch on the roles of synoptic-scale weather events and of mesoscale circulations, the connections between lower and upper atmosphere, and the nature of seasonal and interannual variations.