The Seasonal Behavior of Water
Ice Clouds in the Tharsis and
Valles Marineris Regions of Mars:
Mars Obiter Camera Observations
J. Benson, B. Bonev, P. James, K. Shan,
B. Cantor, M. Caplinger
ICARUS
Presented by Kate Hale
12/9/04
Outline
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Objectives of the study
Why is the study important?
Description of technique
Data
Results
Objectives
• Quantify seasonal variations of cloud characteristics
associated with certain topographical features
(canyons and volcanoes)
• Determine periodicities in data
• Estimate cloud top height
• Determine optical depth of observed clouds to
estimate their water content
Why is this study important?
Past Studies:
• Ground based
• Mariners 6, 7 & 9
• Viking
• Hubble Space Telescope
ALL LIMITED
None able to perform continuous, daily monitoring
Techniques of the study
• Data taken from March 15 1999, to July 31, 2001
• Mars Orbital Camera took images in both red and blue
bandpass range
– In blue the ice clouds appear very bright (high scattering albedo)
separating them from the darker dust clouds
• In 24-hr period a complete global map is obtained of
resolution = 7.5 km/pixel (Daily Global Maps)
– However some missing data at times due to solar conjunction and
incomplete data reception at Deep Space Network (~19 Martian days)
• Visually located areas of high cloud density, then matched
with blue images and cloud area measured
• Thermal Emission Spectrometer (TES) data complemented
visual images
Data - 4 Tharsis region volcanoes
From (D)
Formed from
upward slope
of volcano
Ripple
“W” cloud
(large, bright,
limb clouds)
From (C)
A) Arsia Mons (1˚S, 130˚W by 10˚S, 110˚W)* May 2001
B) Alba Patera (50˚N, 128˚W by 30˚N, 99˚W)* Dec 2000
C) Ascraeus Mons (25˚N, 129˚W by 2˚N, 88.5˚W)* February 2001
D) Pavonis Mons (11˚N, 127˚W by 8˚S, 105˚W)* February 2001
*Window coordinates: (left top, right bottom)
Data- Seasonal for Volcanoes
Aerocentric Longitude:
Angle of Mars in its
orbit around the sun,
measured from the
vernal equinox (Ls = 0
starting northern
hemisphere’s Spring
season)
Observations:
- Olympus and
Ascraeus are similar
- Arsia has constant
cover
- Pavonis Mons had
double peak
Alba Patera
• Alba Patera also has
double peak (highest peak
at 1.2 million km2)
• Anticorrelated with
Olympus and Ascraeus
Data
• Cloud height taken for several days throughout cloudy
season.
- Visual inspection of position relative to volcano
compared against topographical maps of the volcanoes
• Cloud optical depth was calculated from blue images and
the radiance (albedo) of the clouds using the 3 layer model
which was used in modeling Hubble’s observations.
- Observed radiance compared with outside point
surface albedo
- TES data used to estimate dust optical depth
• Water column abundances were calculated from final
calculated cloud depths
Results
• Overlapping of data shows that there is seasonal repeatability
for the Tharsis volcanoes, Olympus Mons, and Alba Patera
• Cloud area on short scale (< 10-15 sols) intensifies in both
size and thickness as the day progresses
• Clouds at Valles Marineris are in form of haze from Spring to
mid-Summer, then small discrete clouds until end of Summer.
• Cloud heights increase as day progresses
– Range for Alba Patera 5.5 – 6.5 km compared to
– Olympus Mons 19 – 21 km
• H2O abundances range from .080 - .820 pr μm for Arsia Mons
to .101 – 1.358 pr μm (pr μm = precipitable microns)