Outer Planets

Some assembly required: Nature's instruction booklet for planetary migration

We once thought planets formed peacefully in situ in their natal disks and subsequently followed their orbits like clockwork. However, there is growing evidence that the typical planetary system forms with "some assembly required" and undergoes a dynamical rearrangement through planetary migration processes. The nature of this migration remains debated, in particular whether the migration is caused by smooth planet-disk interactions or violent multi-body interactions.

Convection in ice mantles: effects of texture and anisotropy

icy moonThe icy mantles of satellites in the outer solar system may transport heat by solid-state convection, which is important because it provides a mechanism for cycling material between a ocean and surface, controls the rate of heat transport, and may produce surface geological features. The style of convection and rate of heat transport depend strongly on ice rheology, which is complex.

The atmospheric circulation of Pluto and Triton as predicted by a general circulation model

A variety of previous studies have investigated the 1D vertical temperature-pressure profiles of Pluto and Triton's atmospheres, while another class of models has investigated the bulk north-south transport of volatiles on these worlds.  However, only recently have modern, 3D general circulation models (GCMs) been applied to Pluto and Triton.

How to Catch a Moon of Pluto (and what to do with it when it's caught)

Our recent discoveries of two small moons orbiting Pluto raise interesting new questions about how the dwarf planet formed. We now know that a total of four outer moons circle around a central "double-planet" comprising Pluto and its large, nearby moon Charon. NASA's New Horizons spacecraft will arrive at Pluto in July 2015, and the new discoveries come just in time for the science planners to target closeup views of the tiny bodies during the flyby.

Close-in Planets: From Hot Jupiters to Super Moons

The closest-in planets, with periods as short as 10 hours, are now a well-established population, thanks to Doppler and transit surveys. They present a number of challenges: how did they form and achieve their tight orbits, and how do they evolve and survive in the face of intense irradiation from their parent stars? Although orbital migration is often invoked, the possibility of in-situ accretion deserves consideration, and Dr. Chiang will review how rocky cores coagulate and acquire gaseous envelopes at the smallest disk radii.

Radio Anatomy of Saturn's Rings with Cassini (Video)

Like the scalpel in the hand of a skilled surgeon, Cassini radio signals have been dissecting Saturn’s rings since 2005.  In a group of special Cassini orbits that place the main ring system between Cassini and the Earth (radio occultation orbits), perturbations in parameters of three nearly pure sinusoidal radio signals (0.94, 3.6, and 13 cm wavelength) simultaneously transmitted by Cassini through the rings are captured at one or more of the ground receiving stations of the NASA Deep Space Network (DSN).

Ice on the Move: From Io to Pluto

It's perhaps no surprise that the cold worlds of the outer solar system often display surfaces covered in ice, though the ice composition is sometimes unexpected, including sulfur dioxide or nitrogen ice, for instance, in addition to water ice.  The motion of these ices as they sublime and condense can have profound effects on these worlds and their atmospheres.  The variable patchy atmosphere of Io, the extreme albedo contrasts seen on small scales on Callisto and on large scales on Iapetus, and seasonal changes in the atmospheres of Pluto and Triton, are all controlled by the movement of

Characterization of dark materials on Iapetus, Phoebe and Hyperion

Iapetus is historically the most intriguing satellite of Saturn because of its color dichotomy. A major advance in the understanding of the origin of the dichotomy has come recently from two fundamental pieces of information. The first was the discovery by Verbiscer et al. (2009) of a ring of dark material that originates in the Phoebe’s neighborhood and spirals down to Iapetus collecting on its leading side.

A Post-Equinox View of Saturn's Rings

Saturn’s Equinox 2009: Oblique lighting exposed vertical structure and embedded objects. The rings were the coldest ever. Dr. Esposito will show how images inspired new occultation and spectral analysis that show abundant structure in the perturbed regions. The rings are more variable and complex than we had expected prior to this seasonal viewing geometry.

A Guide to Lakefront Vacationing on Titan: Hydrocarbon Lakes and their Role in the Methane Cycle.

Observations of Titan’s polar regions reveal hydrocarbon lakes with morphologies and scales similar to terrestrial counterparts. The global distribution, topography, and seasonal variability of these lacustrine features are used to study volatile transport in Titan’s hydrologic cycle. This seminar will review recent observations made by the Cassini RADAR and discuss the constraints they place on the nature of the lakes, their role in Titan's methane cycle, and their evolution over both seasonal and orbital timescales.

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