In situ measurements of the physical characteristics of Titan's environment.

M. Fulchignoni (1) , F. Ferri (2) , F. Angrilli (2) , A.J. Ball (3) , A. Bar-Nun (4) , M.A. Barucci (1) , C. Bettanini (2) , G. Bianchini (2) , W. Borucki (5) , G. Colombatti (2) , M. Coradini (6) , A. Coustenis (1) , S. Debei (2) , P. Falkner (7) , G. Fanti (2) , E. Flamini (8) , V. Gaborit (1) , R. Grard (7) , Michel Hamelin (9) , A.M. Harri (10) , B. Hathi (3) , I. Jernej (11) , M.R. Leese (3) , A. Lehto (10) , P.F. Lion Stoppato (2) , J.J. López-Moreno (12) , T. Mäkinen (10) , J.A.M. Mcdonnell (3) , C.P. Mckay (5) , G. Molina-Cuberos (13) , F.M. Neubauer (14) , V. Pirronello (15) , R. Rodrigo (12) , B. Saggin (16) , K. Schwingenschuh (11) , A. Seiff , F. Simões (9) , A. Svedhem (7) , T. Tokano (14) , M.C. Towner (3) , R. Trautner (7) , P. Withers (3) , J.C. Zarnecki (3)

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
2 CISAS - Centro di Ateneo di Studi e Attività Spaziali “Giuseppe Colombo”
3 PSSRI - Planetary and Space Sciences Research Institute [Milton Keynes]
4 TAU - Department of Geophysical, Atmospheric and Planetary Sciences [Tel Aviv]
5 ARC - NASA Ames Research Center
6 ESA - Agence Spatiale Européenne = European Space Agency
7 ESTEC - European Space Research and Technology Centre
8 ASI - Agenzia Spaziale Italiana
9 CETP - Centre d'étude des environnements terrestre et planétaires
10 FMI - Finnish Meteorological Institute
11 IWF - Space Research Institute of Austrian Academy of Sciences
12 IAA - Instituto de Astrofísica de Andalucía
13 Departamento de Física [Murcia]
14 IGN - Institut für Geophysik und Meteorologie [Köln]
15 Unict - Università degli studi di Catania = University of Catania
16 POLIMI - Politecnico di Milano [Milan]

On the basis of previous ground-based and fly-by information, we knew that Titan's atmosphere was mainly nitrogen, with some methane, but its temperature and pressure profiles were poorly constrained because of uncertainties in the detailed composition. The extent of atmospheric electricity (‘lightning’) was also hitherto unknown. Here we report the temperature and density profiles, as determined by the Huygens Atmospheric Structure Instrument (HASI), from an altitude of 1,400 km down to the surface. In the upper part of the atmosphere, the temperature and density were both higher than expected. There is a lower ionospheric layer between 140 km and 40 km, with electrical conductivity peaking near 60 km. We may also have seen the signature of lightning. At the surface, the temperature was 93.65 ± 0.25 K, and the pressure was 1,467 ± 1 hPa.

Domaines: Astrophysique [astro-ph]; Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Physique des plasmas [physics.plasm-ph]

M. Fulchignoni, F. Ferri, F. Angrilli, A.J. Ball, A. Bar-Nun, et al.. In situ measurements of the physical characteristics of Titan's environment.. Nature, 2005, 438 (8 dec.), pp.785-791. ⟨10.1038/nature04314⟩. ⟨hal-00157795⟩