Outer Planets

Europa’s surface records a complex history of geologic activity including fracture systems driven by tidal stress, which varies daily as Europa executes its eccentric orbit. Obliquity, physical libration, and non-synchronous rotation would also contribute to the pattern of tidal stress on Europa. Hence, we can use observed fracture systems to constrain these rotational parameters. Using cycloids and strike-slip faults, Dr. Rhoden has been able to probe Europa’s rotation state and uncover the first geologic evidence of non-negligible obliquity. Dr.

Whether or not Titan currently possesses a subsurface ocean is crucial for understanding its long-term evolution. In this talk Prof. Nimmo will present two lines of evidence suggesting the existence of a subsurface ocean, probably ammonia-rich.

In 2006 NASA launched a sophisticated robotic explorer to make the first reconnaissance of planet Pluto and its moons, three billion miles from the Sun. That spacecraft is called New Horizons. The principal investigator of New Horizons, Dr. Alan Stern, will describe the mission, it's full objectives, and will describe the new class of planets that Pluto represents.

Dr. Glatzmaier will describe his studies of fluid flows and the magnetic fields they generate in the electrically conducting interiors of terrestrial planets, like the Earth, of giant planets, like Jupiter, and of satellites, like Europa, that orbit around giant planets. Dr. Glatzmaier develops computer models that solve a set of coupled nonlinear differential equations that describe the main physics of the problem in order to simulate the 3D time-dependent evolution of the flows and fields.

The results of the Cassini/Huygens mission raise many questions about the source and fate of methane on Titan. Understanding the methane cycle on Titan is key to understanding its past history and future evolution and provide a context for considering life on Titan that uses methane for its biological solvent. Dr. McKay, a member of the Huygens science team, will describe a new model for Titan's geological cycle that may indicate it's current thick atmosphere is a transient phenomenon.

 Saturn's giant moon Titan has been of considerable interest since the presence of an atmosphere was hinted at one century ago. The NASA-ESA-ASI Cassini-Huygens mission, at Saturn for the last 4 years, has transformed this curious dot in the sky into a remarkably diverse, complex and interesting world, which is in many ways more Earth-like than anywhere in the solar system. This talk will summarize some of Cassini's recent findings with emphasis on the interactions between Titan's surface, atmosphere, and interior.

All landforms on Titan that are unambiguously identifiable can be explained by exogenic processes (aeolian, fluvial, impact cratering, and mass wasting). Previous suggestions of endogenically produced cryovolcanic constructs and flows have, without exception, lacked conclusive diagnostic evidence. Titan might be most akin to Callisto with weather. Dr. Moore will show the results of Landform Evolution Modeling for the purposes of testing this, and other, hypotheses. 

 NASA and ESA have recently selected the Europa Jupiter System Mission (EJSM) as the next Flagship mission to the out solar system. The mission concept consists of a NASA-led Jupiter Europa Orbiter (JEO) and an ESA-led Jupiter Ganymede Orbiter (JGO), which would execute a choreographed exploration of the Jupiter System before entering orbit around Europa and Ganymede, respectively.

The Cassini spacecraft has been orbiting Saturn since 2004, with frequent flybys of the largest moon Titan. With its thick atmosphere rich in nitrogen and hydrocarbons, it was once thought that Titan was covered in a global ocean of methane. Cassini optical and microwave imaging instruments have since revealed a world with a solid surface, strikingly similar in physical appearance to Earth, complete with lakes of liquid methane/ethane in the polar regions.

 An extensive set of thermal measurements of Saturn’s main rings has been returned by the Cassini Composite Infrared spectrometer (CIRS) over the past five years at a variety of ring geometries that are not observable from Earth. The largest temperature changes on the lit face of the rings are driven by variations in phase angle, including an unexpected thermal surge at low phase angles. Temperatures at equinox were retrieved for the first time, as the sun traversed from the south to north side of the rings in mid-August.