Download Molecules in planet atmospheres

Molecules in planetary atmospheres
Emmanuel Lellouch
Observatoire de Paris
Some history…
Kuiper 1944
« The only reason why I
happened to observe the
planets and the 10 brightest
satellites was that they were
nicely lined up in a region of
the sky where I had run out of
programs stars »
Detection of methane in Titan
Vertical profile of methane from
Huygens and Cassini
VIMS
Some history…
CO produced on dayside
from CO2 + h  CO
Yet, more CO on Venus
nightside than on dayside!
Why hunt for molecules in planets?
1. Because we like to see new species and
because planetary spectra can be beautiful
CH3CN in Titan
(IRAM 30-m; Marten et al. 2002)
Why hunt for molecules in planets?
(even in the infrared…)
Detection of C6H6 in Saturn
(ISO; Bézard et al. 2001)
Disk resolved spectroscopy of Io :
detection of S2 in the Pele plume
and even in the UV…
HST/STIS long-slit
spectroscopy of
Pele plume
Spencer et al. 2000
Why hunt for molecules in planets?
2. Because it gives information on chemical
pathways
SATURN
Detection of hydrogen peroxide (H2O2)
on Mars
•Production
HO2 + HO2  H2O2 +O2
•Destruction
H2O2 + h v  2 OH
362 GHz (JCMT)
8 µm (IRTF)
Clancy et al. 2004
Encrenaz (THERESE) et al
2005
Why hunt for molecules in planets?
3. Because it gives information on dynamics
and the couplings with chemistry
CO lines give maps of
- CO vertical profile
- Thermal profile
- Wind velocity
VENUS
Measuring mesospheric winds on Titan
~300 km
~450 km
Moreno and Marten 2005
Why hunt for molecules in planets?
4. Because it gives information on the
interactions between Solar System objects
External water in the outer planets
ODIN
ISO
• Interplanetary dust
• Planetary environments
• Cometary impacts
HERSCHEL
CO in Neptune’s atmosphere
IRAM 30-m: 8x 1 GHz
Discovery (JCMT)
Marten et al. 1991
A dual source?
- internal
- comet impact
Lellouch et al. 2005
Why hunt for molecules in planets?
4bis) Sometimes, it gives us incomprehensible
problems!
Evolution of the Shoemaker-Levy 9 debris
on Jupiter
CO, CS, HCN
HCN
• Chemical effect?
• Dynamical effect?
CO2
Why hunt for molecules in planets?
5. Because it is a way to study exotic
atmospheres (and to make good friends…)
SO2, SO, and NaCl in Io’s atmosphere
(IRAM 30-m)
SO2
Origin?
• Volcanism
• Sublimation equilibrium (not NaCl)
Detection of NaCl in Io’s atmosphere
Why hunt for molecules in planets?
6. Because it tells us things about origin and
evolution of planets
(sorry, this time, I will take a break about
helium and deuterium)
Isotopic ratios in Titan’s atmosphere
12C/13C
SMA
Gurwell 2004
= terrestrial
14N/15N in HCN = 4.5 times less than terrestrial
in N2 (Cassini) = 1.5 times than terrestrial
 ESCAPE of Titan atmosphere + FRACTIONATION in HCN
Why hunt for molecules in planets?
7. Because it is a race and we are ready to
make big efforts for it
CO on Pluto
4 days of good
Weather
Int. time 2090 min.
Bockelee-Morvan
et al. 2001
Stupid galactic contamination
Search for new compounds on Venus from limbspectroscopy during the June 8 transit (T. Fouchet)
OFF
ON
What do you think it happened?
1. The IRAM TAC did not give time
2. The observations had to be stopped quickly
because the telescope started to heat
dangerously
3. The observations were performed but
nothing was detected (even the 50 % deep
CO lines)
4. CO(2-1) only was detected
5. The observations led to the first detection of
SO2 in Venus’ upper atmosphere
What it happened
1. The IRAM TAC did not give time
2. The observations had to be stopped quickly
because the telescope started to heat
dangerously
3. The observations were performed but
nothing was detected (even the 50 % deep
CO lines) – 200 K ripples!!
4. CO(2-1) only was detected
5. The observations led to the first detection of
SO2 in Venus’ upper atmosphere
Detection of J2O on Earth
(Cambridge 2005 DPS meeting)
J2O abundance:
2 bpp*
* bottles
person
per
Why hunt for molecules in planets?
5. … or good enemies…