Europlanet Science Congress 2021
Virtual meeting
13 – 24 September 2021
Europlanet Science Congress 2021
Virtual meeting
13 September – 24 September 2021
EPSC Abstracts
Vol. 15, EPSC2021-440, 2021
European Planetary Science Congress 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Evidence of topographic features on (307261) 2002 MS4 surface

Flavia L. Rommel1,2, Felipe Braga-Ribas1,2,3, Mónica Vara-Lubiano4, Jose L. Ortiz4, Josselin Desmars5,6, Bruno E. Morgado1,2,7, Gustavo Benedetti-Rossi2,7,8, Bruno Sicardy7, Roberto Vieira-Martins1,2, Julio I. B. Camargo1,2, Pablo Santos-Sanz4, Nicolás Morales4, Rene Duffard4, Estela Fernández-Valenzuela9, Giuliano Margoti3, Marcelo Assafin2,10, Chrystian L. Pereira1,2, Yucel Kilic11,12, Eric Frappa13, Jean Lecacheux7, and the co-authors*
Flavia L. Rommel et al.
  • 1Observatório Nacional/MCTIC, R. General José Cristino 77, Bairro Imperial de São Cristóvão, Rio de Janeiro (RJ), Brazil (
  • 2Laboratório Interinstitucional de e-Astronomia - LIneA & INCTdo e-Universo, Rua Gal. José Cristino 77, Bairro Imperial de São Cristóvão, Rio de Janeiro (RJ), Brazil.
  • 3Federal University of Technology - Paraná (UTFPR/DAFIS), Rua Sete de Setembro, 3165, Curitiba (PR), Brazil.
  • 4Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain.
  • 5Institut Polytechnique des Sciences Avancées IPSA, 63 boulevard de Brandebourg, F-94200 Ivry-sur-Seine, France.
  • 6Institut de Mécanique Céleste et de Calcul des Éphémérides, IMCCE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ Paris 06, Univ. Lille, 77, Av. Denfert-Rochereau, F-75014 Paris, France.
  • 7LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France.
  • 8UNESP - São Paulo State University, Grupo de Dinâmica Orbital e Planetologia, CEP 12516-410, Guaratinguetá, SP, Brazil.
  • 9Florida Space Institute, University of Central Florida, 12354 Research Parkway, Partnership 1, Orlando, FL, USA.
  • 10Observatório do Valongo/UFRJ, Ladeira Pedro Antônio 43, Rio de Janeiro (RJ), Brazil.
  • 11Akdeniz University, Department of Space Sciences and Technologies, Antalya, Turkey.
  • 12TÜBİTAK National Observatory, Akdeniz University Campus, 07058 Antalya, Turkey.
  • 13Euraster, 1 rue du tonnelier, 46100 Faycelles, France.
  • *A full list of authors appears at the end of the abstract

Trans-Neptunian Objects (TNOs) are small bodies that orbit the Sun with a semi-major axis larger than Neptune's4. They are thought to be remnants of the Solar System primordial disk and can retain information about the early stages of our planetary system's formation. Since the discovery of Albion3 in 1992, thousands of objects were detected in this orbital region, but only the Pluto system13 and (486958) Arrokoth14 has been visited so far by a spacecraft. Detailed topographic studies of Pluto and Charon6,7 presented superficial features of ~6 km while reprocessed Voyager images of Uranus' largest satellite - Oberon, show a mountain11 of ~11 km. Discovered15 in 2002 the big TNO 2002 MS4 is dynamically classified as a hot classical TNO. Thermal measurements made by Spitzer Space Telescope and Herschel Space Observatory, resulted an area equivalent diameter16 of 934 +/- 47 km and a geometric albedo at V-band of 0.051-0.022+0.036

Stellar occultation is a ground-based method that has been presenting exciting advances in the knowledge of Centaurs' and TNOs' physical properties2,9,10,12 and rings1,8. We predicted and observed seven stellar occultations by 2002 MS4 between 2019 and 2021 under the European Research Council (ERC) Lucky Star project framework. The most successful one involved 116 telescopes from Europe, North Africa, and Western Asia on 8 August 2020. 

Here we will present results about 2002 MS4 size, shape and topographic features. Stellar occultation data show an equivalent diameter of about 800 +/- 24 km. On the projected northern hemisphere, they are evidence of topographic features of about 20 km. Following the procedure described by Johnson and McGetchin in 1973, and assuming that 2002 MS4 is mainly composed of ice with densities between 1.0 - 2.0 g/cm3, this object supports surface features of about 7 km. However, if we consider that ice density increases toward the object's centre, then 2002 MS4 can support more prominent features. Figure 1 presents the projected profile detected on the 8 August 2020 stellar occultation.