Planetary System Influences on Longterm Climatic Habitability

International audienceThe recent and growing realization that many exoplanetary systems have structures very different from our own motivates a reconsideration of what is meant by "Habitable." For instance, although the Earth's orbit is never far from circular, the architecture of exoplanet systems could cause some terrestrial planets around other stars to experience substantial changes in eccentricity. Eccentricity variations could lead to climate changes, including possible "phase transitions" such as the snowball transition (or its opposite). I will describe how giant planets on sufficiently eccentric orbits can excite extreme eccentricity oscillations in the orbit of a habitable terrestrial planet. This shows that the longterm habitability (and astronomical observables) of a terrestrial planet can depend on the detailed architecture of the planetary system in which it resides