| 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: |
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: |
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.
|
| 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: |
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: |
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.
|
