B. Sicardy, T. Bertrand, E. Lellouch, F. Forget, J. Lecacheux, F. Roques, T. Widemann, F. Colas, F. Vachier, F. Braga-Ribas, R. Behrend, P. Santos-Sanz, S. Todd, V. D. Ivanov, M. Gillon, E. Jehin, A. Maury, V. Dhillon, C. Veillet, W. Beisker, D. Herald, E. Frappa, A. Cole, E. F. Young, N. Brosch, S. Kaspi, L. Abe, P. Bendjoya, J.-P. Rivet, L. Di Fabrizio, V. Lorenzi, E. Molinari, A. Carbognani, A. Marchini, G. Leto, R. Sanchez, L. Mancini, P. Machado, M. Bretton, F. Signoret, C. Peterson, L. MolnŠr, S. B. Howell
Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015.
Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ~5 and ~380 km (i.e. pressures from ~ 10 μbar to 10 nbar).
Results. (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ~0.3 are present at 4–7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ~20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere.
methods: observational; methods: data analysis; planets and satellites: atmospheres; techniques: photometric; planets and satellites: physical evolution; planets and satellites: terrestrial planets
Astronomy and Astrophysics
Volume 625, Article Number A42, Number of pages 21