CONSTRAINING ATMOSPHERIC DUST LIFTING ON DIURNAL
TIMESCALES FROM EMIRS SURFACE TEMPERATURE OBSERVATIONS
C. A. Wolfe, Northern Arizona University, Flagstaff, AZ, USA (cw997@nau.edu), C. S. Edwards, Northern Arizona University, Flagstaff, AZ, USA, M. D. Smith, NASA Goddard Space Flight Center, Greenbelt, MD, USA, M.
J. Wolff, Space Science Institute, Boulder, CO, USA.

Introduction: Regional and planet-encircling
dust storms occur episodically on Mars, influencing
the thermal structure and dynamics of the atmosphere. While suspended dust particles are nearly always present in the atmosphere of Mars at some
background level, conditions may arise that promote
vigorous dust lifting to occur and existing local or
small-scale dust storms to grow or coalesce, obscuring vast regions of the planet in a thick dust for periods ranging from a few days to many weeks [1].
When dust storms occur, they often alter atmospheric
circulation [2, 3, 4, 5, 6, 7, 8], change surface albedo
patterns [9, 10, 11] and modify subsequent transport
and deposition of water and CO2 at the poles [12, 13,
14]. Dust storms, regardless of their scale, are a key
aspect of the Martian dust cycle. While a community
effort is being put forth to characterize the conditions
necessary for the onset, growth, and decay of dust
storms, little is still known about their diurnal variability.
Most quantitative dust measurements from orbiters during global dust storm events have provided
dust column amounts that are available only on the
dayside part of the orbit [15]. The highly elliptical
orbit of the Emirates Mars Mission (EMM) spacecraft [16] along with fortuitous regional dust storm
event that occurred near the end of 2021 provide a
unique opportunity to investigate atmospheric dust
lifting on diurnal timescales. Using a numerical
thermal model and Emirates Mars Infrared Spectrometer (EMIRS) surface temperature observations,
an upper limit (in µm) will be placed on the amount
of dust that was lofted from the surface before, during, and after the regional dust storm that occurred
near Syrtis Major. Results from EMIRS observations
will be compared to those made by the Thermal Imaging System (THEMIS) instrument on-board Mars
Odyssey during the same time to help further constrain dust lifting. Together, these measurements will
assist in our understanding of dust storm growth and
evolution on diurnal timescales.
Dataset: Syrtis Major is a well-known dark feature lying between the boundary of the northern lowlands and southern highlands of Mars. The dark, low
albedo color is the result of basaltic lava flows covering much of ancient, gently-sloping shield volcano.
The region often undergoes changes in appearance
[10], with the width of the dark region exhibiting
both seasonal and long-term variations [17, 18]. The-

se changes have been attributed to a brightening
caused by global dust storms, followed by darkening
caused by dust removal through aeolian processes
[19, 20].

Figure 1: EXI (top) and EMIRS (bottom) observations showing the evolution of column dust optical
depth from several regional dust storms occurring
near the end of 2021.
Starting in December 2021, the Emirates Exploration Imager (EXI) and EMIRS instruments monitored a rapidly-evolving regional dust storm as it
grew in size (see Figure 1). On December 29, 2021
(LS 149°; EMM orbit number 154), EXI captured a
fully illuminated disk of Mars centered near Syrtis
Major. As is typical for southern hemisphere winter,
the atmosphere was relatively clear, with only a few
discrete water-ice clouds visible over the plains east
of Syrtis Major. Over the next two weeks, both EXI
and EMIRS show high concentrations of airborne
dust approaching and obscuring much of the Syrtis
Major region. During this time, EMIRS observations
reveal a significant increase in the thickness of the
diffuse dust haze, suggesting the active lifting of dust
from the surface.
Methodology: The depletion and replenishment
of surface dust reservoirs available for dust storm
onset
and
growth
leaves
a
measurable
thermophysical signature (i.e. thermal inertia, albedo) that we will quantify using EMIRS surface temperature observations. Variations in diurnal surface
temperature will be interpreted in terms of addition
or removal of surface dust on an otherwise coarser
regolith. Atmospherically corrected surface temperatures are retrieved using the 15-µm CO2 absorption
band [21].
Employing the KRC numerical thermal model
[22], a variety of layered surface and subsurface

conditions are simulated to produce a multidimensional lookup table. Specifically, we are interested in modeling the removal of a thin layer of finegrained, low thermal inertia, high albedo dust particles on top a substrate with a higher bulk thermal
inertia and lower albedo [23]. Using a host of input
parameters, including LS, latitude, local time, elevation, and dust opacity, surface temperature is derived
for a variety of thermal inertia and surface albedo
values, allowing different dust layer thicknesses to be
modeled.
Surface temperature is modeled as a function of
local time based on data collected near the center of
the Syrtis Major quadrangle (10° N, 60° E). To compute the surface temperature difference and thus constrain the amount of dust that was lifted during the
dust storm, modeled diurnal surface temperature
curves were subtracted from one another. This simple algebraic operation was performed for several
cases, including instances where either surface albedo or thermal inertia were allowed to vary, with the
other remaining input parameters held constant. Figure 2 demonstrates the effect a variety surface and
subsurface conditions have on surface temperature
difference over diurnal time scales.

ture difference derived from EMIRS data acquired
before and after the dust storm event. The surface
temperature difference resulting from dust lifting
depends strongly on the time of day, with surface
temperature decreases typically occurring during the
day and increases during the night. The surface temperature fluctuations induced by dust removal are
largely due to the thermal properties of the dust and
underlying surface material, specifically their thermal
inertias. As the fine grain, low thermal inertia dust is
lifted aloft through various mechanisms, it exposes
the coarse, high thermal inertia surface material below. To place an upper limit on the amount of dust
lifted or removed from the surface, modeled diurnal
surface temperature difference curves from KRC are
compared with EMIRS observations.
Preliminary Results:
Figure 3 illustrates the binned and averaged diurnal
surface temperature differences determined from
EMIRS data acquired before and after the dust storm
event. Due to both local time coverage and the binning method, data is somewhat sparse during the
morning and evening hours. Furthermore, the observed data exhibits a high degree of variability,
which may stem from the rather large region of interest sampled. Despite the sporadic nature of the data
points, there does appear to be some weak agreement
with the modeled data from KRC, specifically a temperature decrease during the daytime hours and an
increase during the nighttime hours.

Figure 2: Modeled diurnal surface temperature difference curves for the Syrtis Major region demonstrating the influence of albedo and dust thickness.
Using the Java Mission-planning and Analysis for
Remote Sensing (JMARS) software suite [24], a query was performed that returned EMIRS pixels occupying the Syrtis Major region (approximately a 13° x
31° rectangular grid) based on EMM orbit number.
Only pixels that were acquired with the center detector were utilized as this detector was found to have
the highest performance. Furthermore, the query restricted returning any pixels with an emission angle
exceeding 70°. Retrieved parameters, including
brightness temperature and column dust optical
depth, were exported to a tabulated CSV file. A Python script was written to ingest the CSV files that
were generated and bin the retrieved parameters by
15-minute local time intervals. The average value of
the retrieved parameter of interest was then computed for each local time bin.
The JMARS query described above was carried
out for a total of 7 EMM orbits (Orbit number 153,
154, 156, 157, 158, 165, 166), with surface tempera-

Figure 3: Binned and averaged diurnal surface temperature differences based on EMIRS surface temperature data before (EMM orbits 153-154) and after
(EMM orbits 165-166) the dust storm event.
Summary and Future Work:
We have successfully demonstrated the ability to
place upper limits on the amount of dust lifted from
the surface of Mars following a regional dust storm.
While the observed EMIRS surface temperature data
between successive EMM orbits shows significant
variability, we find some agreement with surface
temperature differences modeled with KRC. Future
work will involve reducing the variability in EMIRS
surface temperature data, perhaps through refining
the selected region of interest, to constrain dust lifting with a greater degree of accuracy.

References:
[1] Martin, L. J., and Zurek, R. W. (1993), An analysis of the history of dust activity on Mars, J.
Geophys. Res., 98(E2), 3221– 3246.
[2] Conrath, B. J. (1975). Thermal structure of the
Martian atmosphere during the dissipation of the dust
storm of 1971. Icarus, 24(1), 36–46.
[3] Guzewich, S. D., Wilson, R. J., McConnochie, T.
H., Toigo, A. D., Banfield, D. J., & Smith, M. D.
(2014). Thermal tides during the 2001 Martian global-scale dust storm. Journal of Geophysical Research: Planets, 119, 506–519.
[4] Haberle, R. M., Leovy, C. B., & Pollack, J. B.
(1982). Some effects of global dust storms on the
atmospheric circulation on Mars. Icarus, 50(2-3),
322–367.
[5] Leovy, C. B., & Zurek, R. W. (1979). Thermal
tides and Martian dust storms: Direct evidence for
coupling. Journal of Geophysical Research, 84(B6),
2956–2968.
[6] Newman, C. E., Lewis, S. R., Read, P. L., & Forget, F. (2002). Modeling the Martian dust cycle, 1.
Representations of dust transport processes. Journal
of Geophysical Research, 107(E12), L04203.
[7] Wilson, R. J. (1997). A general circulation model
simulation of the Martian polar warming. Geophysical Research Letters, 24(2), 123–126.
[8] Zurek, R. W. (1982). Martian great dust storms:
An update. Icarus, 50(2–3), 288–310.
[9] Cantor, B. A. (2007). MOC observations of the
2001 Mars planet-encircling dust storm. Icarus,
186(1), 60–96.
[10] Szwast, M. A., Richardson, M. I., & Vasavada,
A. R. (2006). Surface dust redistribution on Mars as
observed by the Mars Global Surveyor and Viking
orbiters. Journal of Geophysical Research, 111,
E11008.
[11] Vincendon, M., Audouard, J., Altieri, F., &
Ody, A. (2015). Mars Express measurements of surface albedo changes over 2004–2010. Icarus, 251,
145–163.
[12] Benson, J. L., & James, P. B. (2005). Yearly
comparisons of the Martian polar caps: 1999–2003
Mars Orbiter Camera observations. Icarus, 174(2),
513–523.
[13] Cantor, B. A. (2007). MOC observations of the
2001 Mars planet-encircling dust storm. Icarus,
186(1), 60–96.
[14] Strausberg, M. J., Wang, H., Richardson, M. I.,
Ewald, S. P., & Toigo, A. D. (2005). Observations of
the initiation and evolution of the 2001 Mars global
dust storm. Journal of Geophysical Research, 110,
E02006.
[15] Kleinboehl, A., Spiga, A., Kass, D. M., Shirley,
J. H., Millour, E., Montabone, L., & Forget, F.
(2020). Diurnal variations of dust during the 2018
global dust storm observed by the Mars Climate
Sounder. Journal of Geophysical Research: Planets,
125, E006115.

[16] Amiri, H.E.S., Brain, D., Sharaf, O. et al. The
Emirates Mars Mission. Space Sci Rev 218, 4 (2022)
[17] Sagan, C., Veverka, J., Fox, P., Dubisch, R.,
French, R., Gierasch, P., Quam, L., Lederberg, J.,
Levinthal, E., Tucker, R., Eross, B., Pollack, J. B.,
(1973) Journal of Geophysical Research, 78(20),
4163-4196.
[18] McKim, R. J. (1999). Telescopic Martian dust
storms: a narrative and catalogue. Memoirs of the
British Astronomical Association, 44, 165.
[19] Lee, S. W. (1986). Regional sources and sinks
of dust on Mars; Viking observations of Cerberus,
Solis Planum, and Syrtis Major, LPI Contribution
599: 57-58.
[20] Christensen, P. R. (1988). Global albedo variations on Mars: Implications for active aeolian
transport, deposition, and erosion, J. Geophys. Res.,
93(B7), 7611– 7624.
[21] Edwards, C.S., Christensen, P.R., Mehall, G.L.
et al. The Emirates Mars Mission (EMM) Emirates
Mars InfraRed Spectrometer (EMIRS) Instrument.
Space Sci Rev 217, 77 (2021).
[22] Kieffer, H. H. (2013), Thermal model for analysis of Mars infrared mapping, J. Geophys. Res. Planets, 118, 451– 470.
[23] Edwards, C. S., Nowicki, K. J., Christensen, P.
R., Hill, J., Gorelick, N., and Murray, K. (2011),
Mosaicking of global planetary image datasets: 1.
Techniques and data processing for Thermal Emission Imaging System (THEMIS) multi-spectral data,
J. Geophys. Res., 116, E10008.
[24] Christensen, P. R., et al. (2009) JMARS - A
Planetary GIS, American Geophysical Union, Fall
Meeting 2009.