Lower atmosphere and pressure evolution on Pluto from ground-based stellar occultations, 1988–2016

¹ LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, France
e-mail: bruno.sicardy@obspm.fr
² Observatório do Valongo/UFRJ, Ladeira Pedro Antonio 43, Rio de Janeiro, RJ 20080-090, Brazil
³ Observatório Nacional/MCTIC, Laboratório Interinstitucional de e-Astronomia-LIneA and INCT do e-Universo, Rua General José Cristino 77, Rio de Janeiro CEP 20921-400, Brazil
⁴ Instituto de Astrofísica de Andalucía (IAA-CSIC). Glorieta de la Astronomía s/n. 18008-Granada, Spain
⁵ National Aeronautics and Space Administration (NASA), Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA
⁶ Laboratoire de Météorologie Dynamique, IPSL, Sorbonne Université, UPMC Université de Paris 06, CNRS, 4 place Jussieu, 75005 Paris, France
⁷ IMCCE/Observatoire de Paris, CNRS UMR 8028, 77 Avenue Denfert Rochereau, 75014 Paris, France
⁸ Observatoire de Lille, Université de Lille, 1, impasse de l’Observatoire, 59000 Lille, France
⁹ Southwest Research Institute, Department of Space Studies, 1050 Walnut Street, Suite 300, Boulder, CO 80302, USA
¹⁰ Federal University of Technology – Paraná (UTFPR/DAFIS), Rua Sete de Setembro 3165, CEP 80230-901 Curitiba, Brazil
¹¹ Geneva Observatory, 1290 Sauverny, Switzerland
¹² Astronomical Institute (ASÚ AVČR), Fričova 298, Ondřejov, Czech Republic
¹³ Institute of Physics (FZÚ AVČR), Na Slovance 2, Prague, Czech Republic
¹⁴ National Institute of Water and Atmospheric Research (NIWA), Lauder, New Zealand
¹⁵ Occultation Section of the Royal Astronomical Society of New Zealand (RASNZ), Wellington, New Zealand
¹⁶ Dunedin Astronomical Society, Dunedin, New Zealand
¹⁷ ESO (European Southern Observatory) – Alonso de Cordova 3107, Vitacura, Santiago, Chile
¹⁸ Space sciences, Technologies & Astrophysics Research (STAR) Institute, University of Liège, Liège, Belgium
¹⁹ Physics and Astronomy Department, Appalachian State University, Boone, NC 28608, USA
²⁰ Department of Physics and Astronomy, University of North Carolina – Chapel Hill, NC 27599, USA
²¹ Department of Physics, Central Michigan University, 1200 S. Franklin Street, Mt Pleasant, MI 48859, USA
²² San Pedro de Atacama Celestial Explorations, San Pedro de Atacama, Chile
²³ Grupo de Ciencias Planetarias, Departamento de Geofísica y Astronomía, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de San Juan and CONICET, Argentina
²⁴ Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
²⁵ Instituto de Astrofísica de Canarias, C/ Vía Láctea, s/n, 38205 La Laguna, Spain
²⁶ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
²⁷ Large Binocular Telescope Observatory, 933 N Cherry Avenue, Tucson, AZ 85721, USA
²⁸ Internationale Amateursternwarte (IAS) e. V., Bichler Straße 46, 81479 München, Germany
²⁹ International Occultation Timing Association – European Section (IOTA-ES), Am Brombeerhag 13, 30459 Hannover, Germany
³⁰ International Occultation Timing Association (IOTA), PO Box 7152, Kent, WA 98042, USA
³¹ Canberra Astronomical Society, Canberra, ACT, Australia
³² Western Sydney Amateur Astronomy Group (WSAAG), Sydney, NSW, Australia
³³ Kuriwa Observatory, Sydney, NSW, Australia
³⁴ Astronomical Association of Queensland, QLD, Australia
³⁵ Euraster, 1 rue du Tonnelier 46100 Faycelles, France
³⁶ School of Physical Sciences, University of Tasmania, Private Bag 37, Hobart, TAS 7001, Australia
³⁷ Lowell Observatory, 1400 W Mars Hill Rd, Flagstaff, AZ 86001, USA
³⁸ Department of Astronomy, Wellesley College, Wellesley, MA 02481, USA
³⁹ Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA
⁴⁰ Joseph R. Biden, Jr. School of Public Policy and Administration, University of Delaware, Newark, DE 19716, USA
⁴¹ Data Science Institute, University of Delaware, Newark, DE 19716, USA
⁴² Center for Urban Science and Progress, New York University, 370 Jay St, Brooklyn, NY 11201, USA
⁴³ SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94043, USA
⁴⁴ School of Physics & Astronomy and Wise Observatory, Tel Aviv University, Tel Aviv 6997801, Israel
⁴⁵ Department of Earth and Planetary Sciences and Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 0076100, Israel
⁴⁶ Oukaimeden Observatory, LPHEA, FSSM, Cadi Ayyad University, Marrakech Morocco
⁴⁷ Bankstown, 115 Oxford Avenue, Sydney 2200, New South Wales, Australia
⁴⁸ Craigie, 295 Camberwarra Drive, West Australia 6025, Australia
⁴⁹ Stockport Observatory, Astronomical Society of South Australia, Stockport, SA, Australia
⁵⁰ Mt. John Observatory, University of Canterbury, PO Box 56, Lake Tekapo 7945, New Zealand
⁵¹ Wellington Astronomical Society (WAS), Wellington, New Zealand
⁵² BOSS – Backyard Observatory Supernova Search, Southland Astronomical Society, New Zealand
⁵³ Observatoire de la Côte d’Azur, Université Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire CS 34229, 06304 Nice, Cedex 4, France
⁵⁴ INAF – Telescopio Nazionale Galileo, Rambla J.A. Fernández Pérez, 7, 38712 Breña Baja, Spain
⁵⁵ INAF Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius CA, Italy
⁵⁶ Section of Astrophysics, Astronomy and Mechanics, Department of Physics, National and Kapodistrian University of Athens, 15784 Zografos, Athens, Greece
⁵⁷ Astronomical Observatory of the Autonomous Region of the Aosta Valley, Aosta, Italy
⁵⁸ Astronomical Observatory, Dipartimento di Scienze Fisiche, della Terra e dell’Ambiente, University of Siena, Italy
⁵⁹ INAF – Catania Astrophysical Observatory, Italy
⁶⁰ Department of Physics, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy
⁶¹ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁶² INAF – Astrophysical Observatory of Turin, Via Osservatorio 20, 10025 Pino Torinese, Italy
⁶³ International Institute for Advanced Scientific Studies (IIASS), Via G. Pellegrino 19, 84019 Vietri sul Mare (SA), Italy
⁶⁴ Archenhold Sternwarte, Alt-Treptow 1, 12435 Berlin, Germany
⁶⁵ Schwäbische Sternwarte e.V., Zur Uhlandshöhe 41, 70188 Stuttgart, Germany
⁶⁶ Astronomie Stiftung Trebur, Fichtenstr. 7, 65468 Trebur, Germany
⁶⁷ Technische Hochschule Mittelhessen, University of Applied Sciences, Wilhelm-Leuschner-Straße 13, 61169 Friedberg, Germany
⁶⁸ Roof Observatory Kaufering, Lessingstr. 16, 86916 Kaufering, Germany
⁶⁹ Gabriel Murawski Private Observatory (SOTES), Poland
⁷⁰ Hieronymusstr. 15b, 81241, München, Germany
⁷¹ Stallhofen Observatory, Graz, Austria
⁷² Software Engineering Department, University of Granada, Fuente Nueva s/n 18071 Granada, Spain
⁷³ Sociedad Astronómica Granadina (SAG), Apartado de Correos 195, 18080 Granada, Spain
⁷⁴ Raptor Photonics Llt, Willowbank Business Park, Larne Co. Antrim BT40 2SF, Northern Ireland
⁷⁵ AiryLab SARL, 34 rue Jean Baptiste Malon, 04800 Gréoux Les Bains, France
⁷⁶ Gamaya S.A. Batiment C, EPFL innovation park, 1015 Lausanne, Switzerland
⁷⁷ 49 bd François Mitterrand, Université Clermont-Auvergne, CS 60032, 63001 Clermont-Ferrand, France
⁷⁸ Teplice Observatory, Písečný vrch 2517, 415 01 Teplice, Czech Republic
⁷⁹ Institute of Astrophysics and Space Sciences, Observatório Astronómico de Lisboa, Ed. Leste, Tapada da Ajuda, 1349-018 Lisbon, Portugal
⁸⁰ Agrupación Astronómica de Sabadell, Carrer Prat de la Riba, s/n, 08206 Sabadell, Catalonia, Spain
⁸¹ Astronomical Observatory, University of Siena, 53100 Siena, Italy
⁸² Osservatorio Elianto, Astrocampania, via Vittorio Emanuele III, 84098 Pontecagnano, Italy
⁸³ Ellinogermaniki Agogi School Observatory (MPC C68), Dimitriou Panagea str, Pallini 15351, Greece
⁸⁴ Télescope Jean-Marc Salomon, Planète Sciences, 77060 Buthiers, France
⁸⁵ Club Astro de Mars, Maison communale 07320 Mars, France
⁸⁶ Observatoire des Baronnies Provençales, 05150 Moydans, France
⁸⁷ GAPRA, 2 rue Marcel Paul, 06160 Antibes, France
⁸⁸ Osservatorio Astronomico di Monte Agliale, Cune, 55023 Borgo a Mozzano, Lucca, Italy
⁸⁹ Balcon des Étoiles du pays toulousain, observatoire des Pléiades, 31310 Latrape, France
⁹⁰ Beobachtergruppe Sternwarte Deutsches Museum, Museumsinsel 1, 80538 München, Germany
⁹¹ Cloudbait Observatory, CO, USA
⁹² Calvin College, MI, USA
⁹³ Department of Geology and Geophysics, University of Wyoming, Laramie, WY 82071, USA

Received: 19 September 2018
Accepted: 1 March 2019

Abstract

Context. The tenuous nitrogen (N₂) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft.

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.