The science of extra-solar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and dedicated space missions has resulted in 560-plus planets being detected, and over 1200 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new ESA's Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are?

In the past ten years, we have learned how to obtain the first spectra of exoplanets using transit transmission and emission spectroscopy. With the high stability of Spitzer, Hubble, and large ground-based telescopes the spectra of bright close-in massive planets can be obtained and species like water vapour, methane, carbon monoxide and dioxide have been detected. With transit science came the first tangible remote sensing of these planetary bodies and so one can start to extrapolate from what has been learnt from Solar System probes to what one might plan to learn about their faraway siblings. As we learn more about the atmospheres, surfaces and near-surfaces of these remote bodies, we will begin to build up a clearer picture of their construction, history and suitability for life.

The Exoplanet Characterisation Observatory, EChO, will be the first dedicated mission to investigate the physics and chemistry of Exoplanetary Atmospheres. By characterising spectroscopically more bodies in different environments we will take detailed planetology out of the Solar System and into the Galaxy as a whole.

EChO has now been selected by the European Space Agency to be assessed as one of four M3 mission candidates.

Pluto’s tenuous nitrogen atmosphere was detected by stellar occultations in 1985 and 1988. This atmosphere is poorly known, however, due to the rarity of these events. We report here the first Pluto occultations observed since 1988, on 20 July and 21 August 2002. Our analysis reveals drastic changes undergone by the atmosphere since 1988, namely a two-fold pressure increase, the probable effect of seasonal changes on Pluto over this fourteen year interval.

Dynamics of Venus’ mesosphere (70-110 km) is characterized by the coexistence of two different wind regimes: (1) between 70 and 85 km the vertical amplitude decrease of Venus’ zonal retrograde super-rotation; (2) between 85 and 110 km, a stable, sub-solar to anti-solar (SSAS) flow, driven by solar EUV heating. On July 7-14, 2001 and July 31 – August 4, 2002 we observed Venus with the Aurélie spectrometer on the 1.5-m telescope at Observatoire de Haute-Provence, France. The spectra cover the visible 8660-8730 Å range, in the 5v3 band of 12C16O2, at a resolving power of about 120,000. Seven regions were observed on Venus’ illuminated side at ~ 75° phase angle. About 28 lines from the P and R branches of the 5v3 band were detected and used for wind velocity measurements with an accuracy of 15 to 25 ms-1.

We present an extension of our equilibrium model, initially applied to 51 Peg b (Goukenleuque et al. 2000), to other irradiated extrasolar planets with different orbital distances (up to 1 AU). The model yields the mean atmospheric thermal structure and predicts the reflected spectral flux as well as the thermal flux emerging from such planets, in the visible and in the infrared wavelength ranges.

The recent, concommitant, operation of the Galileo mission to the Jovian system and of the Infrared Space Observatory has provided a wealth of new results on the atmospheric composition of the Giant Planets. These results include (i) first or improved measurements of several elemental and isotope ratios, particularly in Jupiter; (ii) new insights into Jupiter's (and Saturn's) condensible species and tropospheric cloud structure; (iii) a much enriched view of stratospheric hydrocarbon chemistry; and (iv) the discovery of an external source of oxygen into the Giant Planets. These discoveries address key issues such as the origin of Giant Planets, their tropospheric meteorology and stratospheric physico–chemistry and dynamics, and their interaction with the interplanetary medium.

This paper reviews spectroscopic measurements relevant to the chemical modifications of Jupiter's atmosphere induced by the Shoemaker-Levy 9 impacts. Such observations have been successful at all wavelength ranges from the UV to the centimeter. At the date this paper is written, newly detected or enhanced molecular species resulting from the impacts include H2O, CO, S2, CS2, CS, OCS, NH3, HCN and C2H4. There is also a tentative detection of enhanced PH3 and a controversial detection of H2S. All new and enhanced species were detected in Jupiter's stratosphere. With the exception of NH3 (and perhaps H2S and PH3), apparently present down to the 10-50 mbar level, the minor species are seen at pressures lower than 1 mbar or less, consistent with a formation during the plume splashback at 1-100 microbar. NH3 may result from upwelling associated with vertical mixing generated by the impacts. The main oxygen species is apparently CO, with a total mass of a few 1014 g for the largest impacts, consistent with that available in 400-700 m radius fragments. The observed O/S ratio is reasonably consistent with cometary abundances, but the O/N ratio (inferred from CO/HCN) is much larger, suggesting that another N species was formed but remained undetected, presumably N2. The time evolution of NH3, S2, CS2 shows evidence for photochemical activity taking place during and after the impact week.