Study of the Martian atmosphere in the
SPICAM IR experiment on Mars-Express
А. Fedorova1,2, A.Trokhimovsky1,2, L.Maltagliati3,4, S.Guslyakova1,2, O.
Korablev1,2, F. Montmessin3, J.L. Bertaux3, A.Reberac3
and the SPICAM team,
1Space
Research Institute, Moscow, Russia;
2Moscow Institute of Physics and Technology (MIPT);
3LATMOS, France;
4LESIA, OBSPM, Meudon, France.
3MS3, Moscow, 8-12 October, Russia
Martian atmosphere in short

Pressure = 6 mbar , CO2 @ 95 %
(varies with season since atmosphere
condenses on the ground)


Mean Surface Temperature = -50°C
Low water vapor content = several
tens of micrometers in the
atmosphere, but large surface
reservoirs (polar caps)

Suspended Particles ( ~ 0.2) :
–
–
–

Dust from the regolith: strong heating
power (like desert dust)
Global dust storms ( ~ 5-10)
Ice crystals (H2O, CO2): from condensation
(cirrus type)
Earth-like Circulation:
–
–
Hadley Cell @ solstices
Strong signal of stationary and transient
waves at mid-to-high latitudes in
fall/winter
MARS-Express
 SPICAM is a one of seven instruments
onboard of Mars-Express.
• UV spectrometer (118-320 nm)
• IR spectrometer (1-1.7 µm; 0.7 kg)
 It was inserted into Mars orbit on
25 December 2003.
 4.5 Martian Years of observations:
from MY26, Ls 330 (January 2004)
to MY 31, Ls 200 (September 2012)
 The possibility of continuous study
of the atmospheric processes for a
long period of time
Солнце
SPICAM IR – AOTF spectrometer:
Spectral range:
Resolving power:
Spectral resolution:
FOV nadir:
solar occultation:
Надир
Лимб
Марс
1-1.7 µm
2000
3.5 cm-1
0.5-1.2 nm
1°
~0.07°
Ночная сто
рона
*
Звезда
*
Звезда
КА
Орбита
Different observation modes
• Nadir viewing (day side)
O 21D g
– H2O abundance at 1.38 μm
– H2O and CO2 ices
– O2 dayglow
CO2 ice
• Solar occultation
– CO2, aerosols, H2O
• Limb
– Airglow in IR (O21Δg 1.27 μm)
– aerosols
H2O
H2O ice
SPICAM IR nadir measurements
MONITORING OF WATER VAPOUR
(2004-2011)
The Current Picture of water vapor cycle
 The first observations of water vapour cycle
MAWD/Viking (1977-1979)
The Global asymmetry of present Mars climate
The Northern summer is in 6 times more water than in the
southern summer
Only 10-20 precipitated μm corresponds to 1-2 m3 of ice!
 TES / Mars Global Serveyor (1999-2004)
The reference map of water vapor seasonal cycle for the
General Circulation modeling.
The asymmetry is changed.
Interannual variations of water vapor
 Studies and modeling of water cycle : Davies
[1981], Jakosky [1983], Haberle & Jakosky [1990], Houben et
al. [1997], Richardson & Wilson [2002]; Montmessin et al.,
2004; Forget et al., 2006; Montmessien et al., 2007 etc.
o Transport of water between hemispheres
o The role of water clouds in the hemispheric asymmetry
(Montmessin et al., 2004)
o The example: the role of transport in the deposition of
water in the polar caps: perennial water ice at the south
pole of Mars could have a precession-controlled
mechanism. The GCM shows that 21,500 years ago, when
perihelion occurred during northern spring, water ice at the
north pole was no longer stable and accumulated instead
near the south pole with rates as high as 1 mm yr-1
(Montmessin et al., 2007)
WATER IN MARS ATMOSPHERE: RECENT DATA SETS
The search of interannual variability
Search of daily and spatial variations, condensation and evaporation processes
 Mars-Express and MGS experiments can’t give an information about daily
variability but can give information about the interannual and spatial variations
 Different measurements from 1977 MAWD, 1999 TES, and 2004 Mars-Express,
2006 MRO. Key to a long-term interannual variability?
BUT Mars-Express has
demonstrated that different
measurement methods can’t be
used for long-term interannual
comparison
The simultaneous observations of
water vapor by different
spectroscopic instruments on MEX
from near IR to thermal range
shows a different results (Korablev
et al., 2006)
7
Retrieval of water vapour in Martian
atmosphere (SPICAM)
•
Near IR range (1.38 μm band of H2O) is sensitive to
multiple scattering by aerosols in the atmosphere
Dust and ice clouds account for MY27-30
(THEMIS/Mars-Odyssey dust and ice data with
correction)
Numerical technique for radiative transfer modeling in
the dusty atmosphere (SHDOM)
•
Uniform mixing of H2O in the atmosphere (up to the
saturation level) is assumed
•
An important issue is an accurate solar spectrum
(Fiorenza and Formisano, 2005), with MAWD data
correction .
•
Spectroscopic database:
HITRAN 2004-2008
•
Liny-by-line calculations
•
Martian Climate Database V4.3 for temperaturepressure profiles
•
To minimize a noise SPICAM spectra were averaged by
10 spectra for a fitting
Dust optical depth from THEMIS (Mars Odyssey) 1075
cm-1 and 825 cm-1 (M. Smith, 2009)
SPICAM spectrum
Influence of dust account on the retrieval procedure
Water vapour with dust account
H2O, pr.mm
Dust optical depth for 1,38 mkm
(“Dust” - ”No dust”)
Dust single scattering albedo w = 0.971; Asymmetry factor g=0.63
%
A seasonal map of the H2O distribution by SPICAM
H2O, pr.mm
MY27
MY28
MY29
MY30
Ls
Comparison of
MAWD (1977-1979)
TES (1999-2004)
SPICAM (2004-2009)
 The recalculation of MAWD/Viking
1 and 2 measurements in the same
1.38 μm with modern climate
database (GCM 2005) and
spectroscopic dataset (HITRAN
2008)
 A good agreement with SPICAM
measurements in the same 1.38
μm band
Annual water vapour cycle by SPICAM IR
All years together H2O, pr.mm
Example of water vapour loss
during global dust storm at MY28
(seasonal dependence for H2O
averaged on latitude stripe (-45:-55))
MY27
1 km3
of ice
• Good dataset of four Martian years for further analysis
MY28
Summary
• “Nothing” else to add to the retrieval algorithm
• New solar spectra, resulted in more then 10 % increase of water vapour abundance for polar cap,
and up to 20% increase for other areas.
• For the first time water vapour map taking into account dust-clouds scattering, to be compared with
GCM and other instruments results.
SPICAM IR limb measurements
O2 NIGHTGLOW ON MARS
(2010-2012)
The O2 dayglow in 1.27 µm on Mars
The dayside
The O2 emission at 1.27 μm is produced by UV dissociation of ozone
O3 + hn
O(1D) + O2(a1Dg)
220 nm < l < 320 nm
The emission was predicted after the ozone discovery in atmosphere of Mars in spectra
recorded by UV spectrometer onboard of Mariner-7 (Barth, 1971). For the first time the
emission was detected by Noxon et al. (1976) by means of ground-based telescopes. The
maximum values observed in the early spring in both hemispheres are closer to polar regions,
reach 30 MR, and its variations reflect variations of the ozone abundance in the atmosphere.
Seasonal distribution
Deactivation of the emission:
1) The emission at altitudes >20-25 km
O2(a1Dg)
O2(X3Sg) + hn ( ~ 4566 s )
2) Deactivation through collision with CO2
CO2 (<20 km)
O2(a1Dg) + CO2
(k2 ~ 10-20 cm3 s-1)
O2(X3Sg)+ CO2
from January 2004 (Ls=330o) to May 2006 (Ls=50o)
The nightglow О2 (а1Δg) 1.27 μm on Venus and Mars
The O2 emission is produced by oxygen recombination
O+O+CO2
O2(a1Dg)+CO2
Venus
 The O2 emission was known for a long time
 The oxygen emission at 1.27 μm at the night
side of Venus is a product of atomic oxygen
recombination that in turn is a product of
photolysis of CO2 on the dayside and transfers
to the nightside by global circulation in the
upper mesosphere and thermosphere of
Venus which causes the gas motion from
subsolar to antisolar point.
Mars
 The O2 emission was not detected directly up to 2010
 Atomic oxygen which participates in the reaction, is
formed on the dayside of Mars as a result of CO2
photodissociation by solar UV radiation with a
wavelength λ <207.5 nm and transported on the
night side by the subsolar-antisolar circulation. The
transport to the winter polar region is performed by
the Hadley meridional cell.
(Krasnopolsky, Icarus, 2004)
First detection on Mars in 2010
1) Detection of the O2 nightglow
on Mars in 2010 in the OMEGA
experiment on Mars-Express
(Gondet et al., 2010; Bertaux et al.,
2011,2012)
There were three detections of the O2
nightglow on limb at the South and
North Poles. The vertical emission
intensity is 0.24 MR
The O2 nightglow
2) Observations of the O2
nightglow on Mars in 2010-2012
by CRISM experiment on MRO
(Clancy et al., 2011, 2012)
Since July of 2009, the Compact
Reconnaissance Imaging Spectrometer
for Mars (CRISM) onboard the Mars
Reconnaissance Orbiter (MRO) has
obtained limb scans over two orbits at
solar longitude (Ls) intervals of ~30°.
O2 nightglow with SPICAM IR
 This emission is an effective indicator of downward flow of air from the altitudes
where the CO2 photodissociation occurs (i.e. above 70 km). The intensity of the
nightglow emission and the altitude of the nightglow layer are controlled by wind
magnitudes and eddy diffusion , the key chemical reaction rates.
 Since 2010 the OMEGA/MEX does not operate in this spectral range
SPICAM IR
 Good points:
 A campaign of nightglow observations by SPICAM has begun from July 2010
 A new command has been used with a maximal integration time of one spectral point
11.2 ms (5.6 ms is a standard for dayside nadir and solar occultations). One ‘window’ in
the spectral range of 1260-1280 nm. 2 sec for one spectrum
 IR channel of SPICAM/MEX is turned on now during stellar occultations in 2011-2012
and we hope during night limb from summer 2012.
 Bad points:
 low vertical distribution of SPICAM with FOV of 1o , about 20 km at limb near a
pericenter of orbit
 Low sensitivity is not enough for nadir measurements – only limb measurements can be
done
First observations (2010), MY30, Ls 150-160, the South Pole
Vertical distribution of the O2 (a1Δg)
volume emission rate in MR/km can be
retrieved from the slant emission.


N O 2 ( Ro )   nO 2 (l )dl  2  nO 2 ( z )

Ro
z
dz
z  Ro 2
2
1. Tikhonov regularization
2. the Richardson-Lucy algorithm
to deconvolve FOV of SPICAM
3. an inversion of the O2 volume
emission rate in MR/nm for
both deconvolved profiles of
slant emission and profiles with
the SPICAM original resolution
First results for the South Pole:
1. Vertical resolution for the observations varies
from 20 to 35 km. Deconvolution with the FOV
was necessary.
2. Altitude of a peak of the O2 slant emission
varies from 37 to 47 km
The Martian general circulation model by LMD
(LMD GCM, Lefevre et al., 2004; Millour et al., 2008; version 2012)
• a new Martian general
circulation (version 2012)
• Atmospheric circulation,
photochemical cycle, upper
atmosphere processes and
ionosphere
• Plenty of improvements
including Improved Dynamics,
Convection and Turbulence Model,
Improved “dust model” to simulate
observed Martian years (MY24 –
MY30), IR and solar wavelength
radiative effects of clouds,
Improved cloud microphysics etc
A new model well reproduce now
the current MEX and MRO
observations
Comparison of the O2 nightglow with the LMD GCM
(Lefevre et al., 2004; Millour et al., 2008; version 2012)
Black - SPICAM observations;
Red - OMEGA data
Blue – GCM model (dashed blue –
convolved with SPICAM vertical
resolution)
• the altitude of the nightglow maximum for volume emission rate varies
from 45 to 55 km, which corresponds on average the model values.
• The vertically integrated emission rate is in 2 times lower than in the model
– more intense transport?
Vertical distribution of the atomic oxygen
O2(a1Dg)+CO2 (1)
O + O +CO2
Important issue:
the oxygen photochemistry controls the energy budget in the 70 to 130 km altitude range.
Atomic oxygen is known to have an important effect on the CO2 15-μm cooling. The
underestimation of O content would yield an overestimation of the temperature in the
GCM modeling.
Assuming the vertical distribution of O2(a1Δg) is preliminary controlled by photochemistry.
Using appropriate reactions, the equilibrium equation for O2(a1Δg) could be written as:
d [O2 (a1D g )]
1
 k1  [O][O][CO2 ]  O 2 (a 1D g )   k2 O 2 (a 1D g ) CO2 
dt

k1 is the rate coefficient of reaction (1), β is the effective yield; k2 is the
deactivation rate; τ is radiative lifetime of the excited state
1
d
[
O
(
a
D g )]
2
The steady state is reached, when photochemical equilibrium exists:
~0
1
dt
1
1
k1  [O][O][CO2 ] ~

O (a D )   k O (a D ) CO 
2
g
2
2
g
2
1
(  k 2 [CO2 ])
The resulting formula for atomic oxygen:
[O]  [O2 (1D)] 
k1  CO2 
Oxygen profiles and comparison with the GCM
1
(  k 2 [CO2 ])
[O]  [O2 (1D)] 
k1  CO2 
Solid lines: observations
Dashed lines: LMD GCM modeling
The estimated density of oxygen atoms at
altitudes from 50 to 65 km varies from 1.5
1011 to 2.5 1011 cm-3
As the basic values we have taken:
1) the kinetics rate of reaction k1(T) = 9.46 × 10−34
exp(485/T)cm6 molecule-1 seс-1 (NIST dataset) ,
2) the effective yield β =0.75
3) deactivation rate k2=10-20 cm3 molecule-1 seс-1
4) radiative lifetime of the excited state τ =4470 sec.
5) Temperature and atmospheric density vertical profiles
were are taken from the LMD general circulation model.
The O2 nightglow observations (2011-2012)
• 64 observations (from orbit 8302 to 10642) with the O2 nightglow detected at limb for
the North Pole from Ls 250 to Ls 360 and the South Pole from Ls 0 to 120.
• Plenty of observations with vertical resolution better than 40 km
• The black points are indicated emissions detected at limb
• Detection at low latitudes is the O2 day-side afterglow.
Vertical profiles of the O2 emission
• Emission peak at 35-42 km for the North Pole and 45-50 km for the South Pole
• The emission is more intense for the North Pole
Seasonal distribution of O2 for the South and North Poles
Comparison with the GCM O2-O
MR
The vertically integrated emission rate is totally lower than in the model but the South
Pole emission shows more discrepancies
The maximum of emission is shifted for the season compared to the GCM model
The temperature and CO2 density from UV stellar occultations
The South Pole
Simultaneous observations of
atmospheric density
The South Pole Ls 115-160
The North Pole
• Warming of the middle atmosphere
40-70 km is more strong (on 20-30K)
The atmospheric downwelling
circulation over the Pole, which is part of
the equator-to-pole Hadley circulation is
more strong than expected?
The same results by MCS/MRO
McCleese et al.,2008. Not completely
improved by the model?
• The cold layer at 105 km
• The density is much higher
The North Pole Ls 265-275
• Good agreement for density
• Warming in the middle
atmosphere is well reproduced
• Possible cold layer at 120 km
Conclusions
SPICAM IR on MEX is a small instrument performing observations of the
Martian atmosphere:
1)
Mapping of water vapor, search of interannual variability

2)
Good dataset of four Martian years for further analysis
The study of the O2 nightglow as a tracer of polar dynamics
 The estimated density of oxygen atoms at altitudes from 50 to 65 km varies from 1.5 to 2.5 1011 cm-3.
 The South Pole: the GCM model does not well reproduce the emission, atmospheric density and
temperature profiles in the South Pole night. The North Pole: a good agreement with the model
 The differences may reflect the current uncertainties in the kinetics of the production of O2(a1Δg), or
can be due to an inaccurate downward transport of O atoms by the GCM in the polar night region
(especially for the South Pole).
3)
Mapping of O2 dayglow (a tracer of ozone on Mars)
 Validation of Martian GCM with photochemisty, anticorrelation with water vapour
 Validation of kinetic parameters
4)
5)
Vertical distribution of water vapor form solar occultation on Mars

Transport of water, condensation processes

Supersaturation has been detected during the northern spring (Maltagliati et al., 2011)
Dust and water ice clouds studies from solar occultation

Seasonal changes of vertical distribution and particles sizes

Impact on the atmospheric heating in the middle atmosphere