In our Solar System, there are numerous mean-motion resonances for the minor bodies and satellites, but there are no mean-motion resonances between the planets. The first mean-motion resonance in an extrasolar planetary system – the 2:1 resonance between two Jupiter-mass planets around the star GJ 876 – was discovered in 2001. Since then, an increasing number of pairs of planets in or near mean-motion resonances and resonant chains of three or more planets have been detected. I will discuss the dynamics of these systems and the constraints that they provide on the formation and dynamical evolution of planets. Topics will include high-order mean-motion resonances in the HD 202206 and nu Ophiuchi systems and the formation of resonant chains near the inner edge of protoplanetary disks.

 Venus, Earth’s twin, is not only the closest planet to us in the solar system, it the closest to Earth in mass, density and size and yet it evolved very differently than the Earth. Venus has an atmosphere that has 90 times the surface pressure as the Earth with a surface temperature of 460 C. Venus does not have a system of plate tectonics like the Earth which is one of the key reasons that Earth is a habitable planet. So how did two planets with roughly the same physical parameters evolve so differently? The NASA Magellan mission to Venus in the Early 1990’s used radar to image the planet’s surface through the optically opaque atmosphere at ~150 m resolution and showed that Venus has a young surface that had been volcanically resurfaced with the last 500 million years. As much a Magellan informed us about Venus it also left many key questions about Venus’s planetary evolution unanswered. Two missions to Venus, VERITAS by NASA, and EnVision by ESA in partnership with NASA, will return to Venus in the 2030’s with the goal of answering how these planet’s evolved so differently. The answer to this question will help inform how many Earth and Venus like planets are there in other solar systems. Radars play a key role on each mission and this talk will describe their role in these missions to Venus and how in combination with the other instruments hope to resolve one of the key mysteries in planetary science.  

TBA