WIND DIRECTION RECORD OF AEROSOLS OBSERVED BY THE MARS
SCIENCE LABORATORY
C. L. Campbell1 (ccamp93@yorku.ca), J. L. Kloos2, C. L. Smith3, D. Ellison4, C. Hayes1, A. C. Innanen1, J.
E. Moores1. 1Centre for Research in Earth and Space Science, York University, Toronto, ON M3H 1P3, CA, 2University
of Maryland, College Park, Maryland, USA, 3Oberlin College, 173 W Lorain St, Oberlin, OH 44074, USA, 4Jet Propulsion
Laboratory, 4800 Oak Grove Dr, Pasadena, CA 91109, USA

Introduction:
Since the beginning of the mission, the Mars Science Laboratory (MSL, Curiosity) has observed the
behavior of overhead aerosols through movies taken
by the Navigation Camera (Navcam). These movies
are useful to capture a variety of parameters such as
optical depth [1,2] and aerosol motion [3]. With an
average cadence of 3-4 sols, a seasonal record of
observed wind directions can be created and analyzed for five Mars Years (MYs).
Wind studies have been completed at Gale Crater
using the Rover Environmental Monitoring Station
(REMS) [4,5,6]. However, this only provides near
surface winds and the loss of Boom 1 restricts REMS
from properly measuring wind direction if the incoming winds relative to the rover is between 90 and 270
degrees [6]. To fill in the gaps, Mars Global Climate
Models (GCMs) have been used in comparison with
REMS observations [7].
Mars GCMs have shown that wind direction does
change with altitude [3] and this must be taken into
consideration. Data from the Cloud Altitude Observation (CAO) will be included that correlates wind
speed from two observations to calculate altitudes of
overhead water-ice clouds. Altitudes from the CAO
have already predicted clouds between 20-40 km
which seemed to agree with modelled results [3]. By
noting the wind direction associated with these altitudes, the CAO can help pinpoint any patterns associated with altitude and wind direction.
Methods:
Zenith Movies. The atmospheric movie that is analyzed for meteorological wind direction is the Zenith Movie (ZM). It consists of eight frames pointed
vertically (~85) to observe aerosol movement directly above the rover. Due to this pointing, the ZM
has a time constraint of  2.5 hours from local noon
to avoid sun saturation in the frames.
Due to the thin nature of Martian aerosols, an imaging technique is needed. Known as the Mean
Frame Subtraction (MFS), it subtracts the mean
frame by each individual frame to reveal any changes, hence aerosol movement. An example of a raw
and MFS movie is shown in Figure 1.
All ZMs within the data set are given a quality
number to determine what aerosols are within the
frames. If they have more uniform motion, they are

classified as water-ice clouds. Any chaotic movement
is considered dust. Any movie with noticeable
movement is analyzed further by overlaying a compass rose to find meteorological wind direction.

Cloud Altitude Observation. To determine the altitude of the observed wind directions, the CAO will
be used. This observation consists of two eightframed movies, a ZM and Cloud Shadow Movie
(CSM), shown in Figure 2. The vertical pointing of

the ZM allows an angular distance to be calculated
by considering the field of view (FOV) of the
Navcam and pixel size of the image. Dividing the
duration of the movie translates the angular distance
into an angular wind velocity. The CSM on the other
hand is pointed directly at Aeolis Mons (Mount
Sharp) to capture shadow movement across the
mountain. By using a Digital Terrain Model (DTM)
a distance can be calculated and translated into an
absolute velocity by noting the time duration of the
shadows. Comparing the angular and absolute velocity from each movie allows the calculation of altitude
of the observed aerosols.

in MY 34 and 35 are shown in Figure 3. To investigate diurnal effects, data is divided into morning
(06:00-10:00 LTST) and afternoon (14:00-18:00
LTST).

Results from the CAO investigates water-ice altitudes during the Aphelion Cloud Belt (ACB) season.
Shown in Figure 4, each MY indicate a consistent
altitude between 15-40 km, however, some data
points at the start and end of the season have a higher
altitude. This could be due to the presence of CO2
clouds instead of water-ice. A wind direction analysis
will be done on each CAO data point and compared
to the ZM data set.

Results:
ZM data will include all movies from the beginning of the mission till MY 36. The CAO was not
introduced until MY 34 so only 3 MYs of data will
be used.
Preliminary results for wind directions measured

Acknowledgements:
The authors wish to thank the Mars Science Laboratory science team. This work was funded by the
Canadian Space Agency MSL Participating Scientist
program and the Natural Sciences and Engineering
Research Council of Canada (NSERC) Technologies
for Exo-planetary Science (TEPS) Collaborative
Research and Training Experience (CREATE) program.

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