Molecules in planetary atmospheres

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Molecules in planetary atmospheres

• Emmanuel Lellouch
• Observatoire de Paris

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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
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Vertical profile of methane from Huygens and
Cassini
VIMS
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Some history
CO produced on dayside from CO2 h? ? CO Yet,
more CO on Venus nightside than on dayside!
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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)
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Why hunt for molecules in planets?

• (even in the infrared)

Detection of C6H6 in Saturn (ISO Bézard et al.
2001)
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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
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Why hunt for molecules in planets?

• 2. Because it gives information on chemical
  pathways

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SATURN
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Detection of hydrogen peroxide (H2O2) on Mars

• Production
• HO2 HO2 ? H2O2 O2
• Destruction
• H2O2 h v ? 2 OH

Clancy et al. 2004
362 GHz (JCMT)
8 µm (IRTF)
Encrenaz (THERESE) et al 2005
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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
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Measuring mesospheric winds on Titan
300 km
450 km
Moreno and Marten 2005
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Why hunt for molecules in planets?

• 4. Because it gives information on the
  interactions between Solar System objects

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External water in the outer planets
ODIN

• Interplanetary dust
• Planetary environments
• Cometary impacts

ISO
HERSCHEL
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CO in Neptunes atmosphere
IRAM 30-m 8x 1 GHz
Discovery (JCMT) Marten et al. 1991
A dual source? - internal - comet impact
Lellouch et al. 2005
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Why hunt for molecules in planets?

• 4bis) Sometimes, it gives us incomprehensible
  problems!

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Evolution of the Shoemaker-Levy 9 debrison
Jupiter
CO, CS, HCN
HCN

• Chemical effect?
• Dynamical effect?

CO2
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Why hunt for molecules in planets?

• 5. Because it is a way to study exotic
  atmospheres (and to make good friends)

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SO2, SO, and NaCl in Ios atmosphere(IRAM 30-m)
SO2

• Origin?
• Volcanism
• Sublimation equilibrium (not NaCl)

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Detection of NaCl in Ios atmosphere
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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)

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Isotopic ratios in Titans atmosphere
SMA Gurwell 2004
12C/13C 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
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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
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Search for new compounds on Venus from
limb-spectroscopy during the June 8 transit (T.
Fouchet)
OFF
ON
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What do you think it happened?

• The IRAM TAC did not give time
• The observations had to be stopped quickly
  because the telescope started to heat dangerously
• The observations were performed but nothing was
  detected (even the 50 deep CO lines)
• CO(2-1) only was detected
• The observations led to the first detection of
  SO2 in Venus upper atmosphere

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What it happened

• The IRAM TAC did not give time
• The observations had to be stopped quickly
  because the telescope started to heat dangerously
• The observations were performed but nothing was
  detected (even the 50 deep CO lines) 200 K
  ripples!!
• CO(2-1) only was detected
• The observations led to the first detection of
  SO2 in Venus upper atmosphere

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Detection of J2O on Earth (Cambridge 2005 DPS
meeting)
J2O abundance 2 bpp bottles per
person
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Why hunt for molecules in planets?

• 5. or good enemies