V. Dehant is Senior Research Scientist at the Royal Observatory of Belgium, responsible for the operational direction 'Reference Systems and Planetology', and is a part-time professor at the Université Catholique de Louvain. Her research is focused on the interior, rotation, and habitability of the terrestrial objects of our Solar System, mostly in relation to the evolution of their interiors and atmospheres. Professor Dehant is also Principal Investigator and Co-Investigator of several instruments in European Space Agency (ESA) and NASA missions, and has received several awards including the Descartes Prize of the European Union. She is involved in the ESA Space Science Advisory Committee (SSAC) and is a member of the Royal Academy of Belgium (Science Class). She is the author of more than 400 publications. P. M. Mathews served as Senior Professor of Theoretical Physics at the University of Madras in India, and is now retired. His main research interests are in the Earth's nutation and precession, and other concomitant phenomena, as well as the properties of, and processes in, the Earth's deep interior. Professor Mathews is the lead originator of the Mathews-Herring-Buffett (MHB) theory of nutation adopted by the International Astronomical Union and International Union of Geodesy and Geophysics. In recognition of his work on the MHB model of nutation, he was elevated to the Fellowship of the American Geophysical Union (2004). He was elected as a Fellow of the Indian Academy of Sciences in 1975 and of the Indian National Science Academy in 1983. He has published 120 papers in reputable journals.