1,2,1,2,2,5,6,7,2,8,9,10,13,15- 1LAB - Univ. Bordeaux - CNRS - UMR5804, Planetary Sciences, Pessac, France (thibault.cavalie@u-bordeaux.fr)
- 2LIRA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
- 3Liberal Studies, New York University, New York, NY 10003, USA
- 4Department of Astrophysics, American Museum of Natural History, New York, NY 10024, USA
- 5Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
- 6Aix-Marseille Université, CNRS, CNES, Institut Origines, LAM, Marseille, France
- 7Atmospheric and Planetary Physics, STAR Institute, University of Li.ge, Belgium
- 8Laboratoire de Météorologie Dynamique/Institut Pierre-Simon Laplace (LMD/IPSL), Sorbonne Université, CNRS, École Polytechnique, Institut Polytechnique de Paris, École Normale Sup.rieure (ENS), PSL Research University, Paris, France
- 9Instituto de Astrofisica de Andalucia (IAA), CSIC, Granada, Spain
- 10Institut Pierre-Simon Laplace, Sorbonne Université/CNRS, Paris, France
- 11Department of Astronomy, Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA
- 12National Radio Astronomy Observatory, Charlottesville, VA 22903, USA
- 13Space Science Institute, 4765 Walnut Street, STE B, Boulder, CO 80301, USA
- 14Facultad de Ingeniera y Ciencias, Universidad Adolfo Ibanez, Av. Diagonal las Torres 2640, Penalolen, Santiago 7941169, Chile
- 15School of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
The upper atmospheric composition of giant planets can be altered by material originating from external sources. Icy rings and satellites, large comet impacts and interplanetary dust particles are known sources of oxygen species. For example, oxygen species in the stratosphere of Jupiter result from the impacts of the comet Shoemaker-Levy 9 fragments in 1994 (Lellouch et al. 1995, 2002, Cavalié et al. 2014) and from interplanetary dust particles (Moses & Poppe 2017). In Saturn and Neptune, CO was likely provided by an ancient comet impact (Cavalié et al. 2010, Lellouch et al. 2005, Luszcz-Cook et al. 2013). On the other hand, H2O is supplied to Saturn by Enceladus (Hartogh et al. 2011, Cavalié et al. 2019) and its rings (Waite et al. 2018), and by interplanetary dust particles in Uranus and Neptune (Moses & Poppe 2017, Teanby et al. 2022). Because those sources results in different spatio-temporal distributions of species, 3D mapping and temporal monitoring are powerful tools to determine their nature for each planet.
In addition, these sources can also deliver nitrogen and sulfur species, as in Jupiter and Neptune (Lellouch et al. 1995, Marten et al. 1995, Moreno et al. 2017). We can then use the abundance ratios between oxygen, nitrogen and sulfur species as a complementary diagnostic to determine the sources of exogenic material in a given atmosphere.
In this paper, we will present spectral mapping observations of Uranus, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) in 2022 and 2024 as part of projects 2021.1.01034.S and 2022.1.00558.S (PI: S. Luszcz-Cook). These observations were set to map the emission of the CO (J=3-2) and HCN (J=4-3) lines. We will report the first detection of HCN in the stratosphere of Uranus. We will present the retrieved abundances for HCN and CO and compare them with previous estimates. We will also discuss the horizontal and vertical distributions of CO, as derived from the observations, and their implications on the source of CO of Uranus. Finally, we will discuss candidate sources of HCN.
References:
Cavalié et al. 2010. A&A 510, A88
Cavalié et al. 2013. A&A 553, A21
Hartogh et al. 2011. A&A 532, L2
Lellouch et al. 1995. Nature 373, 592
Lellouch et al. 2002. Icarus 159, 112
Lellouch et al. 2005. A&A 430, L37
Luszcz-Cook et al. 2013. Icarus 222, 379
Marten et al. 1995. GRL 22, 1589
Moreno et al. 2017. A&A 608, L5
Moses & Poppe 2017. Icarus 297, 33
Teanby et al 2022. PSJ 3, 96
How to cite: Cavalié, T., Moreno, R., Lefour, C., Luszcz-Cook, S., Fouchet, T., Lellouch, E., Carrion-Gonzalez, O., Benmahi, B., Guerlet, S., Milcareck, G., Clément, N., Dobrijevic, M., de Pater, I., Moullet, A., Moses, J., Leconte, J., Spiga, A., Roman, M., and Fletcher, L.: ALMA spectral mapping of Uranus: first detection of HCN and the determination of the external source of CO, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-767, https://doi.org/10.5194/epsc2026-767, 2026.
