Missions

A one-year postdoctoral position ( renewable for a second year upon satisfactory evaluation) is available as part of the ERC-funded AstroGeo project (Astronomical Solutions over Geological Time), based at the Laboratoire Temps Espace (LTE), Observatoire de Paris, France. The position involves working with Jacques Laskar and his team on the long-term dynamics of the Earth-Moon system and on comparing astronomical solutions with geological data. The aim is to contribute to the development of the next generation of long-term astronomical solutions, particularly for use in paleoclimate studies. The appointed researcher will have the opportunity to be part of a major collaborative project and to develop original approaches for modeling the Earth-Moon system's evolution over geological timescales.

The position is open to highly motivated researchers, either recent PhDs or more experienced scientists.

Activities

According to Milankovitch's theory (Milankovitch, 1941), part of the major past climatic variations is due to changes in solar insolation at Earth's surface, resulting from orbital deformations caused by the gravitational perturbations of other planets. These variations are recorded in stratigraphic archives accumulated over millions of years (Ma). The correlation between geological data and celestial mechanics calculations is now sufficiently robust that geological timescales for the more recent periods are directly based on astronomical solutions (Laskar et al., 2004). Moreover, in the past two decades, considerable efforts have extended this astronomical calibration throughout the Cenozoic, up to 66 Ma (e.g., Gradstein et al., 2020).

However, pushing beyond this limit is difficult, as the chaotic nature of planetary motion prevents tracing orbits further back using celestial mechanics alone (Laskar, 1989). The AstroGeo project aims to overcome this predictability horizon, imposed by gravity, by incorporating statistical approaches and using ancient geological data as additional constraints to refine astronomical solutions.

The postdoctoral researcher will join the interdisciplinary AstroGeo team (Astronomy and Geology) at LTE (Observatoire de Paris) to work on the long-term dynamics of the Earth-Moon system since its formation. The work will build upon previous results obtained by the team (Farhat et al., 2022), with the goal of developing a more comprehensive model than the one used in that initial study. Part of the work will also involve comparing the derived solutions with geological data, especially indicators of the Earth's past precession rate. This research will be conducted in close collaboration with the astronomers and geologists involved in AstroGeo. Most of the computational development will be done in C++ or using the TRIP formal computing system, which was developed by the team and is specifically tailored for celestial mechanics (www.imcce.fr/trip). The researcher may be required to travel in Europe and other regions in connection with the project.

Skills

The candidate must have a solid background in celestial mechanics and Hamiltonian system dynamics. Specific experience with the long-term dynamics of the solar system and the Earth-Moon system will be highly valued, as will familiarity with Milankovitch cycles. Proficiency in scientific programming languages and tools is required (FORTRAN, C++, symbolic algebra systems), along with experience in HPC environments (e.g., MPI, SMP), Unix shell scripting, and collaborative platforms (Gitlab, Overleaf). The ability to adapt to other programming environments is essential, especially for working with TRIP. An excellent command of LaTeX is expected. The position requires strong teamwork skills, autonomy, initiative, and a high level of proficiency in English.

Work Context

LTE is a multidisciplinary research center whose areas of expertise cover themes related to time, space, and the history of science. It brings together around 150 people, organised into 9 research teams, two departments responsible for sovereign missions—namely the definition of legal time and the production of ephemerides—a technology division specializing in metrology, and shared support services.

The position is based at the Paris site of the Paris Observatory. The site includes an administrative cafeteria.

Benefits include: health insurance, maternity/paternity leave, meal subsidies, family allowance for children, partial reimbursement of public transport costs, and pension contributions.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.