Geophysics and Tectonics Seminar - winter-2014

Jan. 31, 2014
noon - 1 p.m.
Geology 3814

Presented By:

• Sue Smrekar - JPL

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With Earth-like size and density, Venus should be Earth’s twin. Instead, it lacks plate tectonics and is shrouded by a hot, dense atmosphere with a run away greenhouse. The dramatic divergence of such initially similar terrestrial planets holds lessons for predicting exoplanet behavior. The history of volatiles is clearly central to understanding climate, and also has a major effect on interior evolution. Venus’ atmosphere has lost significant water, yet the interior may have more water than Earth. What are the constraints on water in the interior? Has lithospheric recycling and thus possible volatile recycling occurred? The initiation of subduction is both the gateway to plate tectonics and a key link between interior convection and lithospheric rheology. Numerous potential subduction sites have been identified on Venus. Most of these zones occur in association with corona (possible small-scale mantle upwelling features) and extensional zones. In this talk I will discuss constraints on water in the interior, the evidence for (and against) subduction, and a ‘new’ model for understanding the link between plumes and possible subduction on Venus. This interpretation is based on 1) laboratory fluid dynamics experiments that couple convection and lithospheric deformation and 2) evidence for current volcanism, plumes and possible subduction from gravity, altimetry, radar images and surface emissivity.

Feb. 7, 2014
noon - 1 p.m.
Geology 3814

Presented By:

• Sarah Sonnett - JPL

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Trans-Neptunian Objects (TNOs) are small bodies with orbits beyond Neptune. Roughly 1/3 of TNOs possess peculiarly neutral colors indicative of fresh surfaces, though these objects are thought to be isolated and inactive. To discern between explanations for these neutral colors, we conducted two surveys to search for homogeneity on the surfaces of neutral TNOs – a brightness variation survey in which we sparsely sampled lightcurves of 38 neutral TNOs to select follow-up targets, and a color variation survey of the 9 follow-up targets to densely sample their rotational lightcurves and obtain rotationally phased colors. Our data showcase a surprising number of rotational lightcurves that can only be explained as binaries (some from within the Haumea collisional family). We also found that one of our objects has the fastest measured rotation period of any outer solar system object at 2.4 or 2.6 hours. I will present these results along with updated amplitude and spin distributions for TNOs and comment on what these data suggest about how the dynamical history of the outer solar system.

Feb. 14, 2014
noon - 1 p.m.
Geology 3814

Presented By:

• Josh Colwell - University of Central Florida

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The standard core accretion model of planet formation proceeds from condensation through aggregation of dust particles to formation of km-scale, or larger, “planetesimals”. Once planetesimals form, collisional accretion is aided by the gravity of the planetesimals and simulations consistently produce planets from this starting point. The formation of planetesimals has been problematic, however. Formation by gravitational instability is hampered by turbulence in the disk, and formation by collisional accretion has to occur quickly enough to avoid a fiery fate of the proto-planetesimals in the central star due to aerodynamic drag in the disk. I’ll present the results of experiments designed to study the conditions under which accretion may occur. The experiments also have implications for the collisional evolution of planetary ring systems, and for regolith evolution on planetary satellites and asteroids.

April 10, 2015
noon - 1 p.m.
Geology 3814

Presented By:

• Alex Patthoff - JPL

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Seminar Description coming soon.