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[email protected] Twitter: @chrisarridge Uranus Pathfinder Exploring the Origins and Evolution of Ice Giant Planets Chris Arridge (UK), Craig Agnor (UK), Nicolas André (FR), Kevin Baines (USA), Leigh Fletcher (UK), Daniel Gautier (FR), Mark Hofstadter (USA), Geraint Jones (UK), Laurent Lamy (FR), Yves Langevin (FR), Olivier Mousis (FR), Nadine Nettelmann (DE), Chris Russell (USA), Tom Stallard (UK), Matt Tiscareno (USA), Gabriel Tobie (FR) and the UP Consortium* With thanks to SEA Ltd. and EADS Astrium. * Comprising 165 scientists in 67 institutes in 13 countries world-wide L. Sromovsky / UW-Madison Space Science and Engineering Centre / Keck Introduction 2/18 • Giant planets account for more than 99% of the solar system. • Ice giants (U/N) are fundamentally different from gas giants (J/S). • U/N-mass exoplanets have been observed – remove observer bias from exoplanet distributions ⇒ U/N exoplanets are common. • The ice giants also have fascinating and unique planetary environments. • Voyager 2 remains the only spacecraft to have returned data from Uranus – 26 years have elapsed since that flyby. • Need new in situ observations to Deming &Seager(2009) constrain models, obtain ground-truth for exoplanet observations, and understand solar system formation. Uranus as an Ice Giant Planet 3/18 UP Consortium Consortium UP • Ice giant: envelope rich in “ices” (H2O, CH4, NH3). • No interior model that is consistent with all constraints (gravity field, magnetic field, heat flux, composition, temperature). (a) N. Nettelmann; (b) Connerney et al. (1987) Seasonal variations 4/18 Obliquity: 98º UP Orbit: 84 Years 2049 1986 2028 Solstice: Rings face-on to Sun 2007 Equinox: Rings edge-on to Sun Based on artwork by M.