Current observation programs

Title Telescope Type Role
Jupiter System JWST ERS Science Team
Are the Enceladus geysers the source of Saturn’s water ? ALMA Cycle 5 PI
Constraining Jupiter’s atmospheric chemistry and dynamics from H2O mapping in ALMA band 5 ALMA Cycle 5 PI
The first direct measurement of Saturn’s stratospheric winds ALMA Cycle 5 Co-I
Constraining the internal and external sources of CO in Saturn’s atmosphere IRTF Standard Co-I
Constraining Jupiter’s atmospheric chemistry and dynamics from post-SL9 species mapping ALMA Cycle 4 PI
HCN emission: a diagnostic of Enceladus cryovolcanic activity and torus dynamics ALMA Cycle 2 Co-I
Probing the vertical structure of Saturn’s storm with ALMA ALMA Cycle 0 PI
Water and related chemistry in the Solar System Herschel Guaranteed Time

Key Program

Associate Scientist
Probing the temperature and chemistry of Saturn’s storm with Herschel Herschel Open Time PI
Probing the Enceladus torus with Herschel Herschel Open Time Co-I
Variability in Ice Giant Stratospheres: Implications for Radiative, Chemical and Dynamical Processes Herschel Open Time Co-I
The spatial distribution of CO in Saturn SMA Standard PI
Observation of an equatorial jet in the atmosphere of Jupiter IRAM-30m Standard PI
The origin of CO in Saturn’s atmosphere VLT Short Program Co-I
Jupiter’s stratospheric HCN, hydrocarbon and temperature fields SOFIA Cycle 3 Co-I

An external source of CO for Uranus

With the Herschel Space Observatory, my colleagues and I have detected CO (carbon monoxide) in the stratosphere of Uranus. The analysis and interpretation of the data demonstate that it is supplied by an external source. Is this oxygen delivered by comets, as in Jupiter (see this post), or by interplanetary dust particles? Complementary observations (e.g., with ALMA) are required to disentangle the two origins.

CO emission of Uranus as observed with Herschel. Different source models produce the vertical profiles shown in the right panel. These profiles translate into the emission lines with the corresponding colors in the left panel. Observation/model comparison proves that CO has an external source.

Reference: Cavalié et al. 2014, Astronomy and Astrophysics 562, A33.

The cometary water of Jupiter

In July 1994, comet Schoemaker-Levy 9 (SL9) spectacularly impacted Jupiter. As comets are water-rich bodies, the detection of water in Jupiter’s stratosphere in 1997 by the Infrared Space Observatory (Feuchtgruber et al. 1997) was suggestive of the cometary origin of the observed water.

(left) Jupiter and comet Shoemaker-Levy 9 fragments. (right) scars in Jupiter’s atmosphere caused by the comet impacts.


However, more than a decade of observations with SWAS, Cassini, and Odin could provide us with additional hints (Lellouch et al. 2002, 2006, Cavalié et al. 2008, 2012), but no formal proof. We have mapped the water emission of Jupiter with Herschel in 2009-2010 with its HIFI and PACS instruments. The spatial resolution combined with the very high spectral resolution of our observations prove that the bulk of Jupiter’s stratospheric water was deposited by comet SL9 in 1994. There is indeed an overabundance of water in the southern hemisphere of the planet, i.e. the impacted hemisphere, and the altitude level of residence of water is only compatible with what is expected from the temporal evolution after such an impact.

The stratospheric water of Jupiter thus originates from the comet Shoemaker-Levy 9.

Spatial distribution (in terms of column density) of water in Jupiter’s stratosphere as observed with Herschel. The overabundance seen in the southern hemisphere is reminiscent of the impacts of comet SL9 in 1994 in this same hemisphere.


This result has led to several press releases:

  • European Space Agency: click here (or here for more details)
  • CNRS (in french): click here
  • Astronomy and Astrophysics (not available anymore)

Reference: Cavalié et al. 2013, Astronomy and Astrophysics 553, A21.