EGU23-14200, updated on 26 Feb 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Past Evolution of the Earth-Moon System. The AstroGeo tools for geological proxies.

Jacques Laskar, Mohammad Farhat, Gwenaël Boué, Pierre Auclair-Desrotour, Matthias Sinnesael, Mickaël Gastineau, and Sem Bendjeddou
Jacques Laskar et al.
  • IMCCE, Observatoire de Paris, PSL University, Sorbonne Université, France (

In recent years, several groups have analyzed or re-analyzed stratigraphic data in order to derive astronomical information on the past evolution of the Earth-Moon system. Depending on the approach and on the type of sediment that is analyzed, the retrieved data are of different nature. For tidal deposits, one may attempt to obtain the number of lunar days in a lunar month, or the number of lunar months per year (e.g. Williams, 2000), or even retrieve the nodal period of the Moon (Walker & Zahnle, 1986). In contrast, for cyclostratigraphic analyses, the derived quantity is the precession frequency of the Earth (e.g. Meyers and Malinverno, 2018). The problem for the geologist is then to derive all the other parameters of the Earth-Moon system from this single initial observation. 
The AstroGeo tools ( are designed to help the geologists in this task by providing conversions from one geological proxy  to all the remaining parameters of the Earth-Moon system  that can be derived from this single observation.  These tools developed in the AstroGeo project rely on the physical model recently developed in Farhat et al. (2022). The AstroGeo lunar tool is the first of a series that will be available for the geologists and astronomers community. It allows to input any of the possible observables of the Earth-Moon system (age, semi-major axis, length of the day, precession frequency and angle of obliquity), with some uncertainty, and to derive all the other parameters by interpolating the results of Farhat et al. (2022). At the same time, new data can be plotted versus the nominal solution, together with the already known data that will be kept in an evolving data base. These tools will be available on the AstroGeo website ( I will present these new tools along with the recent progress of the AstroGeo project.

Ref : Farhat, M., Auclair-Desrotour, P., Boué, G., Laskar, J., 2022, The resonant tidal evolution of the Earth-Moon distance
 Astronomy & Astrophysics, 665, L1

How to cite: Laskar, J., Farhat, M., Boué, G., Auclair-Desrotour, P., Sinnesael, M., Gastineau, M., and Bendjeddou, S.: Past Evolution of the Earth-Moon System. The AstroGeo tools for geological proxies., EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14200,, 2023.