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Geophysics and Tectonics Seminar - fall-2015

Recent Observations of Pluto and its Moons from New Horizons

Sept. 25, 2015
noon - 1 p.m.
Geology 3814

Presented By:

  • Ivy Curren - UCLA
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Saturn Ring Seismology: Complex Interactions Between the Planet, the Rings, and the Moons

Oct. 2, 2015
noon - 1 p.m.
Geology 3814

Presented By:

  • Jim Fuller - Caltech
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The rich dynamics of the Saturn ring and moon systems offer unique opportunities to study the evolution of the planet and its surrounding bodies. For instance, seismology of Saturn is made possible by the gravitational interaction between Saturn and its rings, in which density waves in the rings are excited at Lindblad resonances with Saturn's oscillation modes. The seismic signatures in the rings suggest the existence of stable stratification in the deep interior of the planet, likely created by composition gradients between the core and envelope due to helium sedimentation and/or core erosion. These structures within the planet influence the tidal interactions which drive the outward migration of Saturn's inner satellites. Rapid migration can occur when moons become locked in resonance with Saturn's oscillation modes, driving the moons outward on a planetary evolution timescale.

Melt Migration Through Io’s Mantle The Effects of Magma on the Dynamics of Io's Interior

Oct. 16, 2015
noon - 1 p.m.
Geology 3814

Presented By:

  • Catherine Elder - JPL
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Most planets in the solar system lose their internal heat through convection beneath a stagnant lid. However on Io, tidal heating is so intense that its mantle is partially molten. This magma migrates through Io’s mantle and erupts onto its surface. This is thought to be the main mechanism through which heat is removed from Io’s interior. Previous studies have only considered either solid-state mantle convection or magma migration, but magma generation and migration is not independent from mantle convection. Thus understanding the structure of Io’s mantle and how it loses its internal heat requires considering both mantle convection and magma migration. We use the mantle convection code StagYY, which includes the generation, segregation, and eruption of magma, to conduct two-dimensional numerical simulations of mantle convection in Io’s mantle. This allows us to constrain the distribution of melting in Io’s mantle and test the hypothesis that heat loss through volcanic eruptions dominates over heat loss through stagnant lid convection.

Future opportunities for Planetary Sciences studies ...

Oct. 23, 2015
noon - 1 p.m.
Geology 3814

Presented By:

  • Christophe Dumas - TMT
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Future opportunities for Planetary Sciences studies with the Thirty-Meter-Telescope International Observatory

I’ll present a brief overview of the Thirty-Meter-Telescope project, whose construction on top of Mauna Kea is scheduled to take about eight years, with first-light currently planned for the horizon 2023/24, and start of science operations soon after. I’ll review the expected observing performances of the facility and its first-light instruments, which will combine imaging and spectroscopic capabilities, along with powerful adaptive-optics corrected wavefronts and the use of a laser-guide-star facility in some cases. TMT will enable ground-based exploration of our solar system - and planetary systems at large - at a dramatically enhanced sensitivity and spatial resolution across the visible and near-/thermal- infrared regimes (e.g. ~7km spatial resolution at a wavelength of 1micron on main-belt asteroids, 20km on Galilean satellites, 40km on Titan, etc). TIO operations will meet a wide range of observing needs and the implementation of science programs will take into account the stringent observing time constraints often encountered for observations of our solar system such as, for instance, the scheduling of target-of-opportunity observations, the implementation of short observing runs, or the support of long-term "key-science" programmes.

Prevalence and Properties of Planets: Discoveries from Kepler and K2

Oct. 30, 2015
noon - 1 p.m.
Geology 3814

Presented By:

  • Erik Petigura - Caltech
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Prevalence and Properties of Planets: Discoveries from Kepler and K2

As we mark the twentieth anniversary of the discovery of the first planet orbiting another Sun-like star, the study of extrasolar planets is maturing beyond individual discoveries to detailed characterization of the planet population as a whole. No mission has played more of a role in this paradigm shift than NASA’s Kepler mission. Discoveries from the prime Kepler mission demonstrated that small planets (< 3 Earth-radii) are common outcomes of planet formation around G, K, and M stars. While Kepler detected many such planets, all but a handful orbit faint, distant stars, which are not amenable to precise follow up measurements. NASA's K2 mission has the potential to increase the number of known small, transiting planets around bright stars by an order of magnitude. I will present the latest results from my team's efforts to detect, confirm, and characterize planets using the K2 mission.

The Frequency of Exoplanets: A Kepler-Based Model

Nov. 6, 2015
noon - 1 p.m.
Geology 3814

Presented By:

  • Wes Traub - JPL
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Two studies in planetary dynamics

Nov. 20, 2015
noon - 1 p.m.
Geology 3814

Presented By:

  • Renu Malhotra - Univ. of Arizona
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Two Studies in Planetary Dynamics: (i) Impact Seasons on Mars, (ii) The Mass Function of Planets in the Galaxy

I will present results of new calculations of the asteroidal impact flux on Mars. Mars’ orbit is significantly eccentric and the planet orbits near the inner edge of the asteroid belt where the space density of asteroids has a large radial gradient. The correlated secular dynamics of Mars and the asteroids plays a significant role in modulating the impact flux on this planet. At the present epoch, this leads to a large variation — of about a factor of three — in the impact flux when Mars is near aphelion versus perihelion; significantly, the integrated annual impact flux is lower than would be expected in the absence of correlated secular dynamics.

The second part of the talk will describe some deductions about the planet mass function from the observational data of exoplanets and theoretical considerations of planetary dynamics. I will describe analysis of the observational data from the Kepler space mission which indicates that planetary orbital separations have an approximately log-normal distribution. Adopting some plausible ansatzs for the dynamical stability of N-planet systems to relate orbital separations to planet masses, it appears that the planet mass function is peaked in logarithm of mass, with the most probable value of log m/M? ? (0.6 ? 1.0); a modest extrapolation indicates that Earth mass planets are about ~1000 times more common than Jupiter mass planets.