Transcript La mission Venus Express

Non-LTE emission from
VIRTIS/Venus Express
observations
Pierre Drossart1
With Giuseppe Piccioni2,
Gabriella Gilli3, M. Lopez-Valverde3,
Raphaël Garcia4 and the
VIRTIS/VEX team
1LESIA,
Observatoire de Paris
2IAPS, CNR, Rome;
3IAA, Granada, 4 IRAP, Toulouse
Launch :
9 November 2005
Orbit insertion:
11 April 2006
Today :
~2364 orbits
VIRTIS for Venus Express – 7 years after…
P. Drossart, G. Piccioni
– in mem. A. Coradini
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
3
3M-S3
Aeronomy of Venus
The upper atmosphere of planets exhibit a
large variety of physical processes, essential
to understand the interaction of a planet
with its environment, but these regions are
difficult to sound, and still relatively poorly
explored!
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
4
3M-S3
O2 average emission (L. Soret and JC. Gérard , Liège)
O2 emission
altitude : ~95 km
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
5
3M-S3
VIRTIS O2 Herzberg II spectrum obs.
Cf Migliorini et al – O2 emission altitude ~ 95 – 105 km
Mean spectrum, obtained by averaging about 8700 spectra, acquired in the
period 17-03-2010 – 28-02-2011.
Identification of 8 Herzberg II bands. In addition, 3 Chamberlain bands are
observed.
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
6
3M-S3
OH and O2 emission on Venus
OH altitude emission
~ 95 km as O2
cf Piccioni et al 2009
A.V. Shakun, PhD Thesis 2012
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
7
3M-S3
NO observations
from VIRTIS
on Venus
Garcia-Munoz et
al, PNAS, 2009
NO altitude (from
UV/SPICAV) : ~110 km
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
8
3M-S3
Basics on non-LTE models for
Venus, Mars and the Earth : 1) CO
CO 4.7 µm levels scheme
CO 4.7 µm Vibrational temperatures
Gilli et al. 2011
FB and FH bands: main bands
responsible for the 4.7 µm emission
9 octobre 2012
LTE breakdown for CO(2) occurs at higher
pressure then CO(1) in the 3 planets
Pierre Drossart
Москва, ИКИ РАН
9
3M-S3
Results from CO 4.7 m analysis (I)
• Rotational lines identified according to the
spectral resolution of the instruments
Formisano et al. 2005
Formisano et al.2005
Mars
• In Mars and Venus, FH lines
dominate the emission at 100
km,
FB becomes optically thin
• On the Earth the FB is optically thin at all
upper
altitudes,in
duethe
to the
smallerlayers
abundance of CO.
80-110km
Funke et al. 2007
Venus
100 km 150
km
Earth
Funke et al 2005
68 km
Gilli et a. 2011
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
10
3M-S3
Results from CO
4.7m analysis (I)
• Emitted radiance proportional to the
amount of emitters in opt. thin condition
• FB, and FH lines saturated in the
mesosphere of Venus and Mars (opt. thick
condition)
• FH and FB band do not saturate at any
altitudes on the Earth
Gilli et al. 2011
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
11
3M-S3
Results from CO 4.7 m analysis (II)
(focus on Venus and Mars)
80-110 km
100 km
150 km
Gilli et al. 2011
Data-model comparison for the first time at 4.7 m.
Good overall agreement. In Mars the residuals are within the noise level
The knowledge of the actual thermal structure on Venus and Mars is required
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
12
3M-S3
Results:
VIRTIS-H CO
density (I)
Difficult to find spatial and diurnal
variation, due to the irregular
distribution of the data
Local time
variations
No significant variations with
Local Time observed in this
latitude box
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
13
3M-S3
Basics on non-LTE models for
Venus, Mars and the Earth : 2) CO2
CO2 4.3 m levels scheme
• FB band: Transition
from 001 level to the
ground
• FH, SH bands: arises
from higher energy states
CO2 high energy states directly excited
during daytime by solar absorption.
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
14
3M-S3
Comparative planetology: atmosphere of
the terrestrial planets
SIMILARITIES
• UV, soft X-rays absorption in the
Thermosphere
• IR absorption in the mesosphere
DIFFERENCES
• Venus and Mars thermosphere
colder than on the Earth
• O, CO about 10 times more
abundant on Venus and Mars
• Stronger cooling in the upper
regions of Mars and Venus by the CO2
15-m vibrational excited levels
• CO2 vmr on the Earth is 1000 time
smaller
1.
2.
Limb data from VIRTIS/Vex, PFS/Mex (Formisano et al. 2005) and results from MIPAS/Envisat
(Funke et al. 2007) were used.
Non-LTE models for Venus (Roldan et al. 2000, López-Valverde et al. 2007), for Mars (LopezPuertas and Lopez Valverde 1994) and for the Earth (Lopez-Puertas et al. 2005)
9 octobre 2012
Pierre Drossart
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3
Москва, ИКИ РАН
3M-S
Basics on non-LTE models for
Venus, Mars and the Earth
CO2 4.3 m Vibrational temperatures
• LTE departure at similar
pressure levels for Mars
and Venus, lower pressure
on Earth
• Vibrational temperatures
constant at the top of the
atmosphere
Lopez-Valverde, Gilli,… PSS, 2011
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
16
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VIRTIS observations for CO2 non-LTE
Gilli et al, JGR 2009
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
17
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CO2 4.3-m non-LTE measurements
VIRTIS-M spectra & profiles
VIRTIS-M maps
Gilli et al. JGR, 2009
- CO2 emission peak around 110-120 km
- good S/N up to 160 km
- Higher emission at lower SZA
-Change in the overall shape of the band with
altitude
-The altitude peak is maximum at the centre of the
band (4.32 m)
9 octobre 2012
Pierre Drossart
Москва, ИКИ РАН
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R. Garcia,
2011
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Москва, ИКИ РАН
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Москва, ИКИ РАН
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Москва, ИКИ РАН
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Москва, ИКИ РАН
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Москва, ИКИ РАН
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Москва, ИКИ РАН
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Москва, ИКИ РАН
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Москва, ИКИ РАН
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Что дальше на Венере ?
Venus as seen by Akatsuki on 6 December 2010 from 600 000 km (UV- 380 nm)