The BepiColombo Mercury Imaging X-Ray Spectrometer: Science Goals, Instrument Performance and Operations
Space Sci Rev
(2020) 216:126
https://doi.org/10.1007/s11214-020-00750-2
The BepiColombo Mercury Imaging X-Ray
Spectrometer: Science Goals, Instrument Performance
and Operations
Emma J. Bunce1 · Adrian Martindale1 · Simon Lindsay1 · Karri Muinonen2,3 ·
David A. Rothery4 · Jim Pearson1 · Ivor McDonnell1 · Chris Thomas1 ·
Julian Thornhill1 · Tuomo Tikkanen1 · Charly Feldman1 · Juhani Huovelin2 ·
Seppo Korpela2 · Eero Esko2 · Arto Lehtolainen2 · Johannes Treis5 · Petra Majewski6 ·
Martin Hilchenbach7 · Timo Väisänen2 · Arto Luttinen8 · Tomas Kohout9 ·
Antti Penttilä2 · John Bridges1 · Katherine H. Joy10 · Maria Angeles Alcacera-Gil11 ·
Guilhem Alibert12 · Mahesh Anand4 · Nigel Bannister1 · Corinne Barcelo-Garcia12 ·
Chris Bicknell1 · Oliver Blake1 · Phil Bland13 · Gillian Butcher1 · Andy Cheney1 ·
Ulrich Christensen7 · Tony Crawford1 · Ian A. Crawford14 · Konrad Dennerl15 ·
Michele Dougherty16 · Paul Drumm1 · Raymond Fairbend12 · Maria Genzer17 ·
Manuel Grande18 · Graeme P. Hall1 · Rosie Hodnett1 · Paul Houghton1 ·
Suzanne Imber1 · Esa Kallio19 · Maria Luisa Lara20 · Ana Balado Margeli11 ·
Miguel J. Mas-Hesse21 · Sylvestre Maurice22 · Steve Milan1 · Peter Millington-Hotze1 ·
Seppo Nenonen23 · Larry Nittler24 · Tatsuaki Okada25 · Jens Ormö21 ·
Juan Perez-Mercader26 · Richard Poyner1 · Eddy Robert12 · Duncan Ross1 ·
Miriam Pajas-Sanz11 · Emile Schyns12 · Julien Seguy12 · Lothar Strüder6 ·
Nathalie Vaudon12 · Jose Viceira-Martín11 · Hugo Williams27 · Dick Willingale1 ·
Tim Yeoman1
Received: 5 May 2020 / Accepted: 9 October 2020
© The Author(s) 2020
The BepiColombo mission to Mercury
Edited by Johannes Benkhoff, Go Murakami and Ayako Matsuoka
B A. Martindale
1
School of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH,
UK
2
Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2, 00560 Helsinki, Finland
3
Finnish Geospatial Research Institute FGI, National Land Survey of Finland, Geodeetinrinne 2,
02430 Masala, Finland
4
School of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK
5
Semiconductor Laboratory of the Max-Planck-Society, Otto-Hahn-Ring 6, 81739 Munich,
Germany
6
PNSensor GmbH, Otto-Hahn-Ring 6, 81739 Munich, Germany
126
Page 2 of 38
E.J. Bunce et al.
Abstract The Mercury Imaging X-ray Spectrometer is a highly novel instrument that is designed to map Mercury’s elemental composition from orbit at two angular resolutions. By
observing the fluorescence X-rays generated when solar-coronal X-rays and charged particles interact with the surface regolith, MIXS will be able to measure the atomic composition
of the upper ∼10-20 µm of Mercury’s surface on the day-side. Through precipitating particles on the night-side, MIXS will also determine the dynamic interaction of the planet’s
surface with the surrounding space environment.
MIXS is composed of two complementary elements: MIXS-C is a collimated instrument
which will achieve global coverage at a similar spatial resolution to that achieved (in the
northern hemisphere only – i.e. ∼ 50 – 100 km) by MESSENGER; MIXS-T is the first
ever X-ray telescope to be sent to another planet and will, during periods of high solar
activity (or intense precipitation of charged particles), reveal the X-ray flux from Mercury
at better than 10 km resolution. The design, performance, scientific goals and operations
plans of the instrument are discussed, including the initial results from commissioning in
space.
Keywords Mercury · BepiColombo · X-ray spectrometry · Surface composition · X-ray
emission · Elemental composition
1 Introduction
The Mercury Imaging X-ray Spectrometer (MIXS) is an instrument aboard the BepiColombo Mercury Planetary Orbiter (MPO; Benkhoff et al. 2010; Benkhoff et al. 2020,
7
Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen,
Germany
8
Finnish Museum of Natural History, Pohjoinen Rautatiekatu 13, Helsinki, Finland
9
Department of Geosciences and Geography, Gustaf Hällströmin katu 2, 00560 Helsinki, Finland
10
Department of Earth and Environmental Sciences, University of Manchester, Oxford Road,
Manchester M13 9PL, UK
11
Instituto Nacional de Técnica Aeroespacial, Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejón de
Ardoz, Madrid, Spain
12
Photonis France SAS, Avenue Roger Roncier, 19100 Brive, France
13
Faculty of Science & Engineering, Curtin University, Bentley, Perth, Western Australia 6102,
Australia
14
Department of Earth and Planetary Sciences, Birkbeck College, University of London, London, UK
15
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, 85748 Garching, Germany
16
Blackett Laboratory, Imperial College London, London, UK
17
Finnish Meteorological Institute, Erik Palménin Aukio 1, 00560 Helsinki, Finland
18
University of Aberystwyth, Aberystwyth, UK
19
School of Electrical Engineering, Aalto University, 02150 Espoo, Finland
20
Instituto de Astrofísica de Andalucía, Glorieta de Astronomía s/n, 18008 Granada, Spain
21
Centro de Astrobiología (CSIC-INTA), Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz,
Madrid, Spain
The BepiColombo Mercury Imaging X-Ray Spectrometer
Page 3 of 38
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this issue) designed to map the elemental composition of the surface of Mercury from orbit. MIXS will provide elemental composition data for the regolith and, by inference, the
protoliths from which it was derived, together with providing key evidence for deep crustal
and mantle compositions via excavated materials around and within complex craters and
peak-ring basins, e.g. Frank et al. (2017), Hall et al. (2020). Although MIXS is only sensitive to the first 10-20 µm of the Mercurian regolith, local mixing means that this information still provides critical compositional information about the contribution of the underlying sub-surface geology (plus a small added exogenous mineralogical/chemical component). Indeed, using a lunar analogy, the regolith composition is expected to be a good
proxy for the average composition of underlying crust on the regional distance scales relevant to MIXS-C (Warren 2005), with MIXS-T able to probe the more localised contributions from individual impact features associated with, for example, complex craters and
basins (Hall et al. 2020). This approach has been effectively used before for Mercury,
where MESSENGER’s XRS maps show clear compositional changes across geomorphologic boundaries (such as the edges of the smooth plains units occupying the Caloris and
Rachmaninoff basins) supporting the assertion that the upper regolith surface reflects the
underlying bedrock (e.g. Nittler et al. 2018). Results from lunar and asteroidal X-ray fluorescence (XRF) mappers have also provided similar interpretations about planetary regional geological variation and evolution (e.g. Crawford et al. 2009; Grande et al. 2003;
Narendranath et al. 2011; Okada et al. 1999; Alder et al. 1972; Nittler et al. 2001). Identifying the (...truncated)
