THE DYNAMIC ATMOSPHERIC AND AEOLIAN ENVIRONMENT OF
JEZERO CRATER, MARS
C. E. Newman, Aeolis Research, Chandler, AZ, USA (claire@aeolisresearch.com), R. Hueso, UPV/EHU, Bilbao, Spain, M. T. Lemmon, SSI, College Station, TX, USA, A. Munguira, UPV/EHU, Bilbao, Spain, Á. Vicente-Retortillo, CAB, INTA, Madrid, Spain, V. Apestigue, INTA, Madrid, Spain, G. Martínez Martínez, LPI,
Houston, TX, USA, D. Toledo Carrasco, INTA, Madrid, Spain, R. Sullivan, Cornell, Ithaca, NY, USA, K.
Herkenhoff, USGS Astrogeology Science Center, Flagstaff, AZ, USA, M. de la Torre Juárez, JPL-Caltech,
Pasadena, CA, USA, M. I. Richardson, Aeolis Research, Chandler, AZ, USA, A. Stott, ISAE-SUPAERO, Toulouse, France, N. Murdoch, ISAE-SUPAERO, Toulouse, France, A. Sanchez-Lavega, UPV/EHU, Bilbao,
Spain, M. Wolff, SSI, College Station, TX, USA, I. Arruego Rodriguez, INTA, Madrid, Spain, E. Sebastián,
CAB, INTA, Madrid, Spain, S. Navarro, CAB, INTA, Madrid, Spain, J. Gómez-Elvira, CAB-INTA, Madrid,
Spain, L. Tamppari, JPL-Caltech, Pasadena, CA, USA, D. Viúdez-Moreiras, CAB, INTA, Madrid, Spain, J.
Pla-Garcia, CAB, INTA, Madrid, Spain; SSI, Boulder, CO, USA, Mars 2020 Atmospheres Working Group.

Introduction:
Aeolian processes are the main causes of change
to the Martian surface and atmosphere in the modern
era (1,2). Large dust storms hugely alter atmospheric
temperatures, densities, and circulation, presenting
hazards to robotic and human missions, but atmospheric dust is present year-round, affecting visibility
and solar power (3,4). Yet, despite their importance
to science and exploration, processes that move sand
and raise dust have not been well quantified in situ,
with missions lacking the necessary sensors and/or a
sufficiently active aeolian environment (5-12).
By contrast, the Perseverance rover carries the
most sophisticated atmospheric and dust sensors yet
flown to Mars. The Mars Environmental Dynamics
Analyzer (MEDA; 13) includes novel Radiation and
Dust Sensors (RDS), which detect dust clouds and
dust devils via changes to direct and scattered sunlight every second, simultaneous with MEDA measurements of p, T, wind and RH, and radiative fluxes
from MEDA’s Thermal InfraRed Sensor (TIRS). In
combination, RDS and TIRS downward and upward
SW radiation data provide albedo and albedo changes due to surface dust removal or deposition. These
sensors allow MEDA to track the passage of dusty
phenomena around / over the rover for a large fraction of each sol, and to relate it both to meteorological timeseries and surface changes. Perseverance
also carries the first microphones to operate on Mars,
providing data on turbulence, vortices, and wind
activity (14), and high-resolution cameras including
the Navcams and Mastcam-Z, to image aeolian activity and features, such as dust devils and surface
wind streaks (15,16). Most crucially, Jezero crater
contains many aeolian surface features, imaged both
from orbit (17,18) and since landing, and dozens of
examples of aeolian activity have been observed
over the first 216 sols of the mission, covering early
spring through early summer (Ls ~13-105°), as described below. The Mars 2020 mission is thus a perfect combination of instrumentation and environment
for studying atmospheric and aeolian connections.

Results:
Wind patterns and aeolian surface features are
controlled by regional and local slopes. In situ wind
data confirm atmospheric model predictions (19,20)
that Jezero crater wind directions are driven mainly
by regional (Isidis basin) and local (crater rim) slope
flows, resulting in a reversal of wind direction twice
per sol. Daytime wind speeds vary hugely on subhourly timescales due to convective activity, but
both hourly mean and maximum values are generally
much stronger than those at night (Fig. 1A).

Fig. 1. Minute-average MEDA horizontal (A) wind speed
and (B) direction at 1.45m at Ls~90°. (C,D) Modeled
change in crater rim downslope flows from 00:04 to 03:44
LTST at Ls~90° using the MarsWRF mesoscale model.

Winds blow on average from the ESE from midmorning through sunset (Fig. 1B), and are more
southerly earlier and more easterly later in the day.
The pattern of daytime winds is very similar to that
predicted by both atmospheric models that resolve
the crater slopes and those that do not (19). This
suggests daytime winds are driven mainly by deep,
strong, regional Isidis basin upslope flows, with limited impact of crater slopes during the daytime, when
a thick planetary boundary layer (PBL) means flows
are not confined close to the surface. However, closer inspection and comparison with modeling reveals
a slight decrease in wind speed mid-afternoon, attributed to local crater slopes and associated flows.
Although wind stress (hence the ability to
transport sand or raise dust, if available) increases
with atmospheric density, which is greater at night,
the dominance of daytime wind speeds over those at
night translates to net sand transport towards 276° i.e., from slightly south of east - over the first 216
sols of the mission. This sand transport direction is
consistent with orbital observations of active sand
transport from the ~ESE in and around Jezero crater
(17,18) and with Perseverance observations of wind
tails in Navcam and Mastcam-Z images (Fig. 2A,B).

Fluting in ventifacts observed by Perseverance
along its traverse (Fig. 2C,D) already indicates dominant transport from the WNW (Fig. 2B), which is
consistent with nighttime wind directions but inconsistent with wind stresses being larger during the
daytime at all locations to date. This suggests the
ventifacts formed during anomalous weather conditions (e.g. major dust storm) or a past climate epoch.
Rare ‘gust lifting’ events are linked to the passage of convection cells. In Perseverance’s first 216
sols, Navcam took 30 time-lapse movies and 49 surveys (five image triplets taken all around the rover)
designed to search for dust devils and dust lifting. Of
these, three surveys show dust lifting by non-vortex
wind gusts. Figs. 3 and 4 show data from the largest
event, on sol 117. Based on the relationship of dust
clouds to surface features (Fig. 3A), the first, northcentered triplet (Fig. 3B-D) shows dust being lifted
over ~30s in a line ~N to S. Areas of active dust lifting cannot be clearly differentiated from those with
dust blowing over them, but we estimate a lifting
area of >4 km2. The fifth image triplet (not shown),
taken 5 mins later and centered just N of W, shows a
dust cloud moving away over the delta to the NW of
the rover, consistent with the observed wind direction and estimated delta height wind speed.

Fig. 2. (A) “Wind tails” (as seen in this Navcam image)
indicate wind-driven sand transport directions. (B) Rose
diagram showing orientations of wind tails (blue) and ventifacts (orange) seen along the rover traverse, plus net sand
transport estimated from MEDA winds and densities over
the first 216 sols (red arrow). (C) Ventifact seen by Mastcam-Z. (D) Example of azimuth measurements of flutes,
used to infer the transport direction of abrading grains.

At night, winds since landing blow on average
from the WNW, similar to the expected directions of
nighttime downslope flows on both the Isidis and
Jezero slopes. While Isidis slope flows are predicted
to increase in strength until sunrise, however, the
observed wind minimum around 03:00 LTST is only
found in atmospheric models that resolve Jezero
crater’s rim (19,20). In such models (Fig. 1C,D) the
rim blocks the regional downslope flows, which are
relatively shallow due to a thin PBL at night, but
develops its own strong downslope winds; these
flows extend to the rover’s current location earlier in
the night but then intensify and concentrate on the
rim after ~01:30, causing wind speeds to decrease at
the rover’s location, consistent with observations. As
Perseverance drives to the crater rim, we expect
nighttime wind speeds to increase greatly, which
may result in dominant nighttime aeolian activity
and net sand transport from the WNW.

Fig. 3: (A) Surface features and viewshed. (B-D) The first,
N-centered triplet of Navcam images (trimmed), 14s apart.
(E) Azimuthal pointing of MEDA RDS sensors on sol 117.

Data from MEDA’s RDS photodiodes (Fig. 4C)
provide a more complete picture of this event. The

vertical FOV of the lateral sensors is ~20-30° above
the horizontal, with azimuthal pointing as in Fig. 3E,
hence their signals can be interpreted as follows:
Dust is raised and forms low dust clouds, producing
the small lat6 and larger lat7 initial peaks; as lifting
ceases, the dust is blown away at low altitudes to the
WNW, moving sideways out of the lat6 FOV and
below the lat7 FOV; as the cloud reaches the delta
front, it rises and moves fully into the lat7 FOV, then
moves below it again as it continues traveling away
from the rover, producing the large, long, and
smooth second lat7 peak. Other peaks are likely due
to dust raised by a previous gust front passing the
rover to the S/SW or diffuse dust activity to the E.

thus suggest that gust lifting events are triggered by
strong winds aligned in gust fronts behind the leading wall of strong convection cells, with these fronts
(on average) perpendicular to the background wind
direction. This is consistent with the pattern of dust
lifting and transport seen on sol 117.

Fig. 5. (A) As in Fig. 1D but now showing daytime convection cells advected over Jezero at Ls~60°. (B) Snapshot
of lifted dust flux in a MarsWRF LES of Jezero.

Fig. 4: MEDA (A) wind direction, (B) speed, and (C) RDS
for 20 mins covering the sol 117 Navcam survey. Timing
of the five image triplets is shown as vertical dotted lines.

All imaged gust lifting events to date occurred
during the period of strong convective activity from
~10:30-16:00 LTST, which manifests as large temporal variability in wind speed (Fig. 1A; 4B), temperature, and other meteorological timeseries. On sol
117 this included a sequence of 24 SuperCam microphone recordings. The microphone signal is sensitive to the product of wind speed and its standard
deviation (21) and two recordings made during the
largest peaks in the MEDA wind data were strongly
saturated (Fig. 4B), indicating particularly intense
and variable winds. The timescale of the variations is
consistent with the walls of convection cells passing
overhead ~4-7 times per hour (periods of 8.6 to 15
minutes), advected by large-scale daytime upslope
winds. Similar activity was reported for the InSight
landing site (22,23), but with fewer peaks per hour,
and has long been predicted for Mars, both by analogy with Earth’s deserts (24) and in Large Eddy Simulations (LES) (25,26). These cells consist of strong,
warm updrafts concentrated in narrow cell walls and
weaker, cooler downdrafts in cell centers, with surface winds blowing toward the walls to conserve
mass. As convection cells are advected over the region, the background and cellular near-surface winds
have the same direction behind the leading cell wall
and combine constructively to produce peak wind
speeds there. This is also seen in the wind field of
the MarsWRF mesoscale simulation (Fig. 5A). We

Output from the high-resolution MarsWRF LES
is used to calculate dust lifting for a threshold wind
stress of 0.008 Pa, and shows similar gust lifting
events occurring along gust fronts (Fig. 5B). We
speculate that a gust front responsible for the second
large wind gust shown in Fig. 4B intensified shortly
after it passed the rover, exceeding the threshold
wind and producing the observed dust lifting. These
results suggest ‘gust lifting’ in Jezero is produced by
gust fronts with wind speeds exceeding a threshold
that is some unknown amount greater than 15 ms-1.
Daytime convective vortices and dust devils are
common in Jezero crater. While dust lifting by wind
gusts appears relatively rare, dust lifting by convective vortices is very common, with dust devils in
30% of movies and surveys designed to seek them
(e.g. Fig. 6), and frequently in other images also.

Fig. 6. (left) Frames every 28s from a Navcam dust devil
movie at ~12:10 LTST on sol 148. (right) Difference between each image and the average, enhancing changes.

The signature of all passing convective vortices
is highly distinctive in wind and pressure and often
in temperature and longwave flux. Further, MEDA’s
RDS photodiodes allow us to identify those vortices
with significant dust content. See the abstract of
Hueso et al. for more details. Correcting for gaps in
coverage, results show on average >4 daytime vortex
pressure drops of >0.5 Pa per sol, with a peak of

>1.15 vortices per hour from 12:00-13:00 LTST. Of
these vortices, ~25% produced a decrease in RDS
top7 signal of greater than 0.5%, indicating sufficient
dust content to significantly block incoming sunlight.
This is a lower bound on the percentage of dusty
vortices, due to the sun-rover-vortex geometry.
However, even 25% would make Jezero’s vortices
far dustier than those observed by other missions.
Dustier vortices typically have larger pressure
drops and maximum wind speeds, which are expected to be correlated (27). This is consistent with
stronger tangential winds - perhaps combined with a
pressure drop ‘suction’ effect - producing greater
dust lifting. Exceptions may have passed on the side
of the rover opposite the sun and thus only appear to
be less dusty. However, we find little correlation
between the approximate vortex diameter and the
pressure drop or dust content of the vortex.
Applying the same technique to InSight data, we
find the peak number of vortex pressure drops >0.5
Pa from Ls~13-105° is nearly 2 per hour. However,
if we correct for InSight daytime winds being ~twice
as fast as in Jezero (hence vortices are blown past
~twice as fast), we find nearly as many vortices are
produced at InSight as in Jezero. We also find a similar distribution of vortex diameters and intensities.
Peak pressure drops >8Pa were found during the
equivalent seasonal period at InSight (28), compared
to a peak of ~6.5Pa in Jezero, while peak vortexassociated wind speeds up to 31ms-1 were found at
InSight (12), similar to the 32ms-1 in Jezero. At both
sites, these were inferred to cause surface changes
seen in imaging, such as motion of surface grains
and appearance of nearby dust devil tracks at InSight
(11,12), or the appearance of surface grains on the
rover deck and motion of surface drill tailings at
Perseverance. Yet puzzlingly, InSight never imaged
a single dust devil, in stark contrast to Perseverance.
Local dust lifting was detected (via RDS/TIRS
albedo changes) four times in association with vortex
passage, providing direct data on threshold conditions needed to raise dust. We find no local dust lifting by vortices for tangential wind speeds < 15 ms-1
or central pressure drops < 2.6 Pa. This minimum
wind speed for dust lifting is comparable to that
measured regularly in association with passing convection cells, yet such speeds alone have not been
observed to raise dust locally, suggesting the vortical
nature of the encounter may be important. See the
abstract of Vicente-Retortillo et al. for more details.
Discussion:
Dust devils and wind gusts could contribute
equally to background dust lifting. An outstanding
question for Mars is what maintains the background
dust haze: dust devils or lifting by non-vortical wind
stress. We find that >30% of dust devil surveys /
movies clearly contain dust devils, while gust lifting
events were found in <4% of surveys / movies.

However, the huge sol 117 gust lifting event may
have raised dust over >4 km2. By contrast, we estimate the largest dust devil imaged would have swept
out an area 1/10th as large. While the other two gust
lifting events were far smaller, and larger dust devils
were inferred from MEDA data, it is feasible that
dust lifted by gust fronts might have equaled that
lifted by vortices over this period, unless events such
as that on sol 117 are very rare. More data are needed to assess this and to look for seasonal variations.
Significance for understanding threshold conditions for dust lifting. A related question is what
threshold conditions must be exceeded for sand motion or dust lifting to occur. We find local dust lifting
by vortices occurs only for winds > ~15 ms-1, which
was also the minimum reported by (12) at which
surface darkening (inferred as dust lifting by a passing vortex) was observed at InSight. However, winds
of 15 ms-1 have been observed at some point by most
surface missions to carry wind sensors (11,12,29-31)
but have not been observed to raise dust outside of
vortex encounters, or to move sand. While Perseverance measured wind speeds of 15ms-1 shortly before
imaging huge gust lifting activity, no dust was raised
locally. Combined with a lack of similar events either imaged or detected by MEDA RDS in most periods with similarly strong wind speeds, we assume
that the gust front strengthened after passing over the
rover, hence the winds associated with dust lifting
are unknown. Thus a notional 15 ms-1 threshold appears limited to dust lifting by a vortex, which may
involve additional (e.g. pressure drop) effects.
Why is Jezero crater so active compared to most
other landing sites? The ability of gust fronts associated with convection cells to - albeit rarely - raise
large amounts of dust differs from observations at all
prior landing sites. Further, the fraction of vortices
that are dusty is far higher than at all previous sites
for which this fraction was known. The contrast with
InSight is particularly striking, as it has equivalent
size, number, and intensity of vortices to Jezero, but
has yet to definitively detect any dust devils. Identifying the cause of this difference, such as surface
properties affecting dust lifting, will have major implications for understanding dust lifting across Mars.
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