Yutong Shi
Title:
Source-to-sink system reconstructed by water-related landforms in NW-Hellas region, Mars.
Abstract:
The climate of early Mars remains one of the most debated issues in Martian science, with contrasting hypotheses proposing conditions from warm and wet to cold and arid. Investigating the morphology and spatiotemporal distribution of water-related landforms, together with the structure and composition of sedimentary deposits of possible aqueous origin, provides a direct approach to constraining paleoclimate and habitability. Here we present a case study of the northwestern Hellas region from a source-to-sink perspective, combining evidence from fluvial landforms and basin deposits to reconstruct regional paleo-hydrological systems and geological evolution.
Sacha Gavino
Title:
Compact planetary systems shaped by three-body resonances, a geometrical visualization.
Abstract:
A large fraction of known multi-planet systems are compact: neighbouring orbits are separated by only a few mutual Hill radii, and their mutual perturbations decide whether the system survives for billions of years or disrupts within a few thousand orbits. Using N-body simulations of Earth-mass, coplanar three-planet systems integrated for up to 10^10 years, I show that lifetimes rise exponentially with orbital spacing but are punctuated by narrow spikes where systems live more than a million times longer than expected. These anomalously stable systems are captured in isolated three-body mean-motion resonances (resonances involving all three planets). I will explain the effect in terms of the repeating geometry of planetary conjunctions, and try to connect it to observed compact resonant chains such as Kepler-60, Kepler-80 and Kepler-223.