First observation of CO at 345 GHz in the atmosphere of Saturn with the JCMT. New constaints on its origin

International audienceWe have performed the first observation of the CO(3-2) spectral line in the atmosphere of Saturn with the James Clerk Maxwell Telescope. We have used a transport model of the atmosphere of Saturn to constrain the origin of the observed CO. The CO line is best-fit when the CO is located at pressures less than (15± 2) mbar with a mixing ratio of (2.5±0.6)×10-8 implying an external origin. By modelling the transport in Saturn's atmosphere, we find that a cometary impact origin with an impact 200-350 years ago is more likely than continuous deposition by interplanetary dust particles (IDP) or local sources (rings/satellites). This result would confirm that comet impacts are relatively frequent and efficient providers of CO to the atmospheres of the outer planets. However, a diffuse and/or local source cannot be rejected, because we did not account for photochemistry of oxygen compounds. Finally, we have derived an upper limit of 1×10-9 on the tropospheric CO mixing ratio

Scientific rationale of a Saturn probe mission

We describe the main scientific goals to be addressed by future in situ exploration of Saturn

First results on Martian carbon monoxide from Herschel/HIFI observations

We report on the initial analysis of Herschel/HIFI carbon monoxide (CO) observations of the Martian atmosphere performed between 11 and 16 April 2010. We selected the (7-6) rotational transitions of the isotopes ^{13}CO at 771 GHz and C^{18}O at 768 GHz in order to retrieve the mean vertical profile of temperature and the mean volume mixing ratio of carbon monoxide. The derived temperature profile agrees within less than 5 K with general circulation model (GCM) predictions up to an altitude of 45 km, however, show about 12-15 K lower values at 60 km. The CO mixing ratio was determined as 980 \pm 150 ppm, in agreement with the 900 ppm derived from Herschel/SPIRE observations in November 2009.Comment: Accepted for publication in Astronomy and Astrophysics (special issue on HIFI first results); minor changes to match published versio

Observation of water vapor in the stratosphere of Jupiter with the Odin Space Telescope.

International audienceThe water vapor line at 557 GHz has been observed with the Odin space telescope with a high signal-to-noise ratio and a high spectral resolution on November 8, 2002. The analysis of this observation as well as a re-analysis of previously published observations obtained with the SubmillimeterWavelength Astronomy Satellite seem to favor a cometary origin (Shoemaker-Levy 9) for water in the stratosphere of Jupiter, in agreement with the ISO observation results. Our model predicts that the water line should become fainter and broader from 2007. The observation of such a temporal variablity would be contradictory with an IDP steady flux, thussupporting the SL9 source hypothesis

Detection of water vapor on Jupiter with the Odin space telescope

The Infrared Space Observatory (ISO) has detected water vapor in the stratospheres of the giant planets and Titan and CO2 on Jupiter, Saturn and Neptune (Feuchtgruber et al. 1997, 1999, Lellouch et al. 1999). The presence of the atmospheric cold trap implies an external origin for H2O (interplanetary dust, sputtering from the satellites and /or rings, large meteoritic impacts). The H2O submillimeric line at 557 GHz was detected by the Submillimeter-Wave Astronomy Satellite (SWAS) in 1999 and 2001 (Bergin et al. 2000, Lellouch et al. 2002), but the vertical profile and the column density derived from the observations are different from the one obtained from ISO mesurements (Lellouch et al. 2002).The swedish sub-millimeter satellite Odin carries out a long lasting monitoring of Jupiter's H20 (110-101) 557 GHz line, since its launch in 2001. As an example, the high resolution H2O spectrum obtained on November 8th, 2002, will be presented and discussed here. Spectral analysis combined with the use of our photochemical model (Ollivier et al. 2000, adapted for Jupiter) provides new clues which help understanding the discrepancy between the ISO and SWAS results

Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS): following the water trail from the interstellar medium to oceans

Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS) is a space-based, MIDEX-class mission concept that employs a 17-meter diameter inflatable aperture with cryogenic heterodyne receivers, enabling high sensitivity and high spectral resolution (resolving power ≥106) observations at terahertz frequencies. OASIS science is targeting submillimeter and far-infrared transitions of H2O and its isotopologues, as well as deuterated molecular hydrogen (HD) and other molecular species from 660 to 80 μm, which are inaccessible to ground-based telescopes due to the opacity of Earth’s atmosphere. OASIS will have <20x the collecting area and ~5x the angular resolution of Herschel, and it complements the shorter wavelength capabilities of the James Webb Space Telescope. With its large collecting area and suite of terahertz heterodyne receivers, OASIS will have the sensitivity to follow the water trail from galaxies to oceans, as well as directly measure gas mass in a wide variety of astrophysical objects from observations of the ground-state HD line. OASIS will operate in a Sun-Earth L1 halo orbit that enables observations of large numbers of galaxies, protoplanetary systems, and solar system objects during the course of its 1-year baseline mission. OASIS embraces an overarching science theme of “following water from galaxies, through protostellar systems, to oceans.” This theme resonates with the NASA Astrophysics Roadmap and the 2010 Astrophysics Decadal Survey, and it is also highly complementary to the proposed Origins Space Telescope’s objectives