PTYS/LPL Colloquium Schedule 2011/2012

DATE EVENT TIME
Tuesday, Aug 23 2011 LPL Colloquium:
TBA

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Aug 30 2011 LPL Colloquium:
TBA

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Sep 6 2011 LPL Colloquium: Mark Sykes:
Dr. Mark Sykes
Planetary Science Institute

"Dawn at Vesta"

Abstract:

The NASA Dawn mission launched on September 27, 2007, and traveled to its first target, Vesta, using solar electric propulsion. Approaching Vesta, it conducted a Moon search, and entered (very very slowly) into orbit on August 11, 2011. Vesta is the second largest asteroid in the main belt and is covered with basalt. It is the source of a large family of asteroids and possibly 6% of the meteorites that fall on Earth. Hubble observations showed a large impact structure covering the southern hemisphere of the asteroid, which is thought to be the origin of Vesta's asteroid family. Dawn is revealing the detailed structure of this feature, showing what may be an interesting central peak well off-set from the center. Vesta is heavily cratered with much mass-wasting as well as albedo and color variations across its surface. Extensive troughs girdle much of its equator. The northern hemisphere is still largely in shadow. Dawn will study Vesta for about a year before departing for its second target, Ceres, the smallest planet in the solar system.


Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Sep 13 2011 LPL Colloquium: Matthias Rempel:
Dr. Matthias Rempel
High Altitude Observatory/
University Corporation for Atmospheric Research

"Numerical Simulations of Sunspots: From the Scale of Fine Structure to the Scale of Active Regions"

Abstract:
Over that past five years magneto-convective sunspot models have seen a dramatic improvement to the point at which simulations of entire sunspots with sufficient detail for resolving sunspot fine structure are possible. After a brief review of recent developments I will focus on three different classes of numerical sunspot models. 1.) Sunspot simulations at the highest currently affordable resolution that focus on details of sunspot fine structure: I will highlight the magneto-convective processes that are responsible for the energy transport, filamentation and driving of the Evershed flow in sunspot penumbrae. 2.) Sunspot models at lower resolution that can be evolved for time scales of several days in computational domains with horizontal extents beyond 50 Mm: These models start to address the subsurface field and flow structure of sunspots and their surroundings as well as processes related to sunspot decay. In addition, these simulations are used as a testbed for helioseismic inversion methods. 3.) Sunspot models on the scale of active regions: These models capture the last stages of the flux emergence and sunspot formation process in the upper most 10 to 20 Mm of the convection zone. After the initial flux dispersal due to the strong expansion of emerging flux a re-amplification of flux into ~3 kG sunspots are found as a robust result.

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Sep 20 2011 LPL Colloquium: Thomas Sharp:
Dr. Thomas Sharp
Professor at Arizona State University

"Shock Metamorphism in Chondrites: Constraints on Impact History of L chondrites"

Meteorites are fragments of planets and asteroids that provide insight into planet formation and solar system processes. The assembly of planets and asteroids involved hyper-velocity collisions that are recorded in meteorites as shock metamorphism. Shock features include deformation, phase transformations, recrystallization, melting and crystallization. These shock effects have been used to estimate shock pressures by comparing them to features produced in shock-recovery experiments. The shock classification and pressure-calibration developed by Stoffler et. al (1991), which has been widely adopted by meteoriticists, implies that highly-shocked chondrites have experienced shock pressures from 50 to 90 GPa, suggesting high impact velocities between asteroids. Localized melting in shocked meteorites results in shock-melt veins and pockets that commonly crystallize at high pressure and record the pressure-temperature conditions of melt crystallization. The shock pressures estimated from melt crystallization are 18 - 25 GPa, which are significantly lower than those based on shock recovery experiments. We have used melt-vein crystallization and solid-state phase transformations to estimate shock pressures and durations. We find that the maximum shock pressure recorded in melt-vein crystallization is 26 GPa and the shock duration can be up to several seconds. Modeling the shock associated with various impact scenarios, we infer that the impact on the L-chondrite parent body at about 500 Ma involved a large impacting body (2- 10 km) and modest relative velocity (3 to ~ 7 km/s).

Kuiper Space Sciences: Room 308
3:30 pm
Monday, Oct 10 2011 TAP Colloquium-Burkhard Militzer:
Dr. Burkhard Militzer
University of California, Berkeley

"Helium Rain and Core Erosion in Gas Giant Planets Predicted from Ab Initio Simulations"

Abstract:
This talk will describe how data from the Galileo mission to Jupiter has been combined with ab initio computer simulations to demonstrate that there is helium rain on this planet [1]. Then we analyze the possibility for the cores inside of giant planets to erode with time because, at temperatures of 10000K and megabar pressures, different core materials may dissolve into the layer of metallic hydrogen above. We start our analysis with water ice since it is assumed to be one of the more volatile components in giant planet cores. We discuss new crystal phases of this material that were recently predicted with ab initio methods [2]. Based on Gibbs free energy calculations, we show that water ice dissolves into metallic hydrogen at megabar pressures and temperatures above 3000K. This demonstrates that the cores of Jupiter and Saturn have, at least partially, been eroded [3]. We conclude by presenting recent results for core erosion of heavier core materials.


Steward: Room N210
4:00 pm
Tuesday, Oct 11 2011 LPL Colloquium:
Dr. Drake Deming
Professor
University of Maryland

"Infrared Light from Extrasolar Planets"

Abstract:

Infrared radiation from extrasolar planets was first detected in 2005 using Spitzer. Following the first detections, the field has exploded with over two dozen transiting planets characterized by Spitzer, Hubble, and increasingly by ground-based observations. Current topics of study include the spectra of exoplanet atmospheres, the presence of atmospheric aerosols and haze, and the circulation of energy by supersonic winds. Within the next decade, we expect to achieve the detection and characterization of a super-Earth exoplanet orbiting within the habitable zone of a nearby M-dwarf star.

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Oct 18 2011 LPL Colloquium:
Dr. Frank Gyngard
Washington University, St. Louis

"You're Older Than You Think: Constraining Timescales Before Solar System Formation with Grains of Stardust"

Abstract:
Presolar grains are literally astrophysical fossils leftover from long dead stars and were incorporated into some primitive meteorites. These fossils, termed stardust, predate the formation of the Solar System and escaped its isotopic homogenization, retaining their original compositions. Determining absolute ages of these grains by applying typical chronometer schemes, such as Pb-Pb dating, are challenging both experimentally and theoretically. Recent advances in estimating the Galactic Cosmic Ray exposure ages of some unique stardust grains, using isotopic measurements from both NanoSIMS and noble gas mass spectrometers, allow us to place constraints on the amount of time dust spent in the interstellar medium before incorporation into the early Solar System. And by the way...you are stardust.

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Oct 25 2011 LPL Colloquium:
Dr. John Bradley
Lawrence Livermore National Laboratory

"Analytical SuperSTEM for Planetary Materials Science"

Abstract:
A new generation of (60-300 keV) scanning transmission electron microscope known generically as "SuperSTEM" provides enhanced analytical capabilities for interrogation of materials. Key electron optical innovations include spherical aberration (Cs) correctors that enable a sub-Å electron probe and sub-Å spatial resolution, and monochromators that reduce energy spread in the incident probe from ~1 eV in a conventional STEM to ~0.1 eV in SuperSTEM, comparable to XAS and XANES and with the additional benefit of >100X improved signal-to-noise. Crystal structures can be imaged and spectroscopically analyzed with single-atomic-column resolution. Liquids in fluid inclusions and implanted gases (including H and He) can be detected in-situ. Optical properties (UV-VIS-near IR) of extraterrestrial materials can be measured down to the nanoscale. Detection limits for minor/trace elements are improved such that quantitative measurements of some extend to the ~200 ppm level in electron transparent specimens.

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Nov 1 2011 LPL Colloquium:
Dr. Lucy Ziurys
Professor
UA Department of Astronomy and Chemistry

"Organics, Minerals, and Isotopes: A Radio Astronomical View of Pre-Solar History"

Abstract:

Understanding the connection between the interstellar gas and the pre-solar nebula is crucial in understanding solar system formation and the origin of life. Important ingredients in this regard are both organic and inorganic materials, while isotopic composition provides insight into stellar origins and Galactic Chemical Evolution. Using the telescopes of the Arizona Radio Observatory (ARO), we have been examining the organic inventory in molecular clouds and the origin of organic chemistry. Molecular line observations have been conducted which trace the history of carbon in stellar nucleosynthesis, its ejection into the interstellar medium, and its subsequent incorporation into dense molecular clouds. A similar study is being conducted to trace metal-containing compounds and their cycling through interstellar gas. New observations have also been carried out to further constrain circumstellar and interstellar isotopic ratios, including 14N/15N. These observational studies are supported by a laboratory high-resolution spectroscopy program utilizing millimeter/sub-mm direct absorption and Fourier transform microwave techniques. Results of these studies will be presented, and their implications for astrobiology.


Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Nov 8 2011 LPL Colloquium:
Dr. Wayne Roberge
Rensselaer Polytechnic Institute

"Multifluid Shear Flows and Electrodynamic Heating of Primitive Solar System Bodies"

The discovery and recent confirmation of enantiomeric excesses in some extraterrestrial amino acids lends credence to a long-held notion, that chondritic meteorites were important sources of prebiotic molecules on Earth. The subject of this talk is the thermal history of chondrite parent bodies (CPBs), a crucial issue for understanding the prebiotic chemistry therein. Two mechanisms for heating asteroids have been studied extensively in the past: the decay of short-lived radionuclides and induction heating. However it has been pointed out by others that the age discrepancy between CAIs and chondrules poses difficulties for radioactive heating of the CPBs. I will demonstrate that classical induction heating is also ruled out because it is based on a subtle misconception. In the process of correcting this problem, we have discovered a related process which we call electrodynamic heating. Electrodynamic heating is physically correct, operates in weakly-ionized protoplanetary disks as well as fully-ionized plasmas, and predicts heating rates which are virtually identical to induction heating for a given set of physical conditions. The prospects for explaining CPB thermal histories in the context of electrodynamic heating will be discussed.

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Nov 15 2011 LPL Graduate Student Colloquium:
Meghan Cassidy
Graduate Student in the Department of Planetary Sciences

A Review of: "Detection of Emerging Sunspot Regions in the Solar Interior"
Ilonidis et al., Science 333.993 (2011)


Cecilia Leung
Graduate Student in the Department of Planetary Sciences

A Review of: "Chaos Terrain, Storms, and Past Climate on Mars"
Kite et al., JGR 116, E10002 (2011)


Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Nov 22 2011 LPL Graduate Student Colloquium:
Robert Zellem
Graduate Student in the Department of Planetary Sciences

"Demonstrating the Capability of Palomar/TripleSpec for Exoplanet Observations: An Emission Spectrum of
HD 209458b"

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Nov 29 2011 LPL Graduate Student Colloquium:
Melissa Dykhuis
Graduate Student in the Department of Planetary Sciences

A Review of: "Mineralogical Characterization of Some V-Type Asteroids, in Support of the NASA Dawn Mission"
De Sanctis et al., MNRAS 412, 2318 (2011)

Corwin Atwood-Stone
Graduate Student in the Department of Planetary Sciences

A Review of: "Lithospheric Drift on Early Mars: Evidence in the Magnetic Field"
Kobayashi and Sprenke, Icarus 210, 37 (2011)

Kuiper Space Sciences: Room 308
3:30 pm
Thursday, Dec 1 2011 Geosciences Colloquium--Dr. Tom Zega:
Professor Tom Zega
Department of Planetary Sciences and
Lunar and Planetary Lab
University of Arizona

"Laboratory Analysis of Rocks from Space: Insights into the Chemistry of the Early Solar System and Ancient Stars"

Host: Esther Posner

Haury (Anthropology): Room 129
4:00 pm
Tuesday, Jan 17 2012 LPL Colloquium:
Dr. Hal Levison
Southwest Research Institute

"Tackling Some Issues in Planet Formation --- From Mars's Size to a Fast Formation of Neptune"

Abstract:

The standard model of planet formation has difficulties explaining some of the features observed in our Solar System. Of particular note, it predicts that Mars should be as massive as the Earth. In addition, it has difficulty in building the cores of the giant planets before the nebula disappeared. Here, I will argue that current models of planet formation are missing two important processes - planetesimal-driven migration and collisional grinding. I will
present new simulations that include these processes. Preliminary results suggest a heretofore unknown and radical
mechanism for building the outer planets.


Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Jan 24 2012 LPL Colloquium:
TBA

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Jan 31 2012 LPL Colloquium:
TBA

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Feb 7 2012 LPL Graduate Student Colloquium:
Melissa Dykhuis
Graduate Student in the Department of Planetary Sciences

A Review of: "Late Miocene Dust Shower from the Break-up of an Asteroid in the Main Belt"
Farley et al., Nature 439, 295 (2006)


Corwin Atwood-Stone
Graduate Student in the Department of Planetary Sciences

A Review of: "Equilibrium Resurfacing of Venus: Results from New Monte Carlo Modeling and Implications for Venus Surface Histories"
Bjonnes et al., Icarus 217 (2012)


Kuiper Space Sciences: Room 308
3:30 pm
Thursday, Feb 9 2012 LPL Colloquium:
Dr. Larry Nittler
Carnegie Institution of Washington

"Hermeochemistry: The composition of Mercury from MESSENGER X-ray, Gamma-ray, and Neutron Measurements"

Abstract:
Elemental abundances at the surface of a rocky planet reflect both the original composition of the body and the various processes that have shaped the surface over billions of years. NASA's MESSENGER spacecraft has been in orbit around Mercury since 18 March 2011, and includes X-ray, Gamma-ray and neutron spectrometers designed to characterize the chemical composition of the planet's surface. This talk will discuss how elemental abundances are determined remotely from orbit as well as initial results indicating a planetary surface formed by partial melting of a highly chemically reduced, but not highly volatile depleted, silicate mantle. Implications for models of Mercury's origin and evolution will be discussed.


Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Feb 14 2012 LPL Graduate Student Colloquium:
James Keane
Graduate Student in the Department of Planetary Sciences

A Review of: "A low mass for Mars from Jupiter's early gas-driven migration." Walsh et al., Nature 475 (2011)


Sarah Morrison
Graduate Student in the Department of Planetary Sciences

A Review of: "Dependence of a planet's chaotic zone on particle eccentricity: the shape of debris disk inner edges." Mustill et al., MNRAS 419 (2012)

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Feb 21 2012 LPL Colloquium:
Dr. Edward C. Stone
David Morrisroe Professor of Physics
California Institute of Technology

"The Voyager Journey to Interstellar Space"

Abstract:
Launched in 1977 on a journey to the giant outer planets and beyond, Voyager 1 and 2 are now at 119 and 97 AU, exploring the spatial and dynamical properties of the heliosheath as the subsonic solar wind approaches the boundary of the heliosphere. Voyager 1 is in a stagnation region in the northern heliosheath, with a slow wind speed, enhanced magnetic field, and continuing changes in the intensities of particles accelerated in the outer heliosphere and of cosmic ray electrons and nuclei that are diffusing in from nearby regions of the Galaxy. In contrast, at Voyager 2 in the southern heliosheath the flow is faster and slowly turning tailward. These and other observations will be discussed in the context of models of the interaction of the solar and interstellar winds that are evolving as the Voyager journey to interstellar space continues.

Dr. Stone's host is Dr. Randy Jokipii

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Feb 28 2012 LPL Graduate Student Colloquium:
Gabriel Muro
Graduate Student in the Department of Planetary Sciences

Modeling the Thermal and Orbital Evolution of Mimas


Donna Viola
Graduate Student in the Department of Planetary Sciences

A Review of: "Olivine-Respiring Bacteria Isolated from the Rock-Ice Interface in a Lava-Tube Cave, a Mars Analog Environment" Popa et al, Astrobiology 1 (2012)


Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Mar 6 2012 LPL Colloquium:
Dr. David Wilner
Associate Director
Harvard-Smithsonian Center for Astrophysics

"Millimeter-wave Insights into Planet-Forming Disks around Young Stars"

Abstract:
The circumstellar disks that arise naturally from the star formation process are the sites where planets are born. Observations at millimeter wavelengths play a key role in probing these disks by providing direct access to the cool dust and gas that trace the bulk of the disk mass, with no contrast problem from starlight. I will discuss results from our recent observations of nearby 1-10 Myr old disks from the Submillimeter Array on Mauna Kea,
Hawaii, designed to provide insight into disk evolution processes and planet-forming potential. Remarkably, a significant population of these disks show compelling evidence that planet formation is well underway. Finally, I
will touch on the incredible advances expected with the international Atacama Large Millimeter Array, now under construction and starting early science.

Dr. Wilner's host is Dr. Ilaria Pascucci

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Mar 27 2012 LPL Graduate Student Colloquium:
Cecilia Leung
Graduate Student in the Department of Planetary Sciences

Sky Beard
Graduate Student in the Department of Planetary Sciences

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Apr 10 2012 LPL Graduate Student Colloquium:
Ethan Schaefer
Graduate Student in the Department of Planetary Sciences
"Vaduz, an Unusual Fresh Crater on Mars: Evidence for Impact into a Recent Ice-rich Mantle"

Meghan Cassidy
Graduate Student in the Department of Planetary Sciences
"Erupting Coronal Sigmoids and Multipolar Magnetic Structure"

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Apr 17 2012 LPL Colloquium:
TBA

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, Apr 24 2012 LPL Graduate Student Colloquium:
Kelly Miller
Graduate Student in the Department of Planetary Sciences

A Review of: "Origin and Evolution of prebiotic Organic Matter as Inferred from the Tagish Lake Meteorite"
Herd et al., Nature 332 (2011)


Michelle Thompson
Graduate Student in the Department of Planetary Sciences

"Comparative Mineralogy, Microstructure and Compositional Trends in the Sub-Micron Size Fractions of Mare and Highland Lunar Soils"

Kuiper Space Sciences: Room 308
3:30 pm
Tuesday, May 1 2012 LPL Colloquium:
Dr. Conel Alexander
Carnegie Institution of Washington

Dr. Alexander's host is Professor Tom Zega

"The Comet-meteorite Connection, and the Sources of Volatiles in the Terrestrial Planet Region"

Determining the source(s) of H, C and N in the terrestrial planet region is important for understanding not only the origin of life on Earth, but also dynamical processes in the solar protoplanetary disk (nebula) and during planet formation. Primitive chondritic meteorites are asteroidal fragments that retain records of the first few million years of Solar System history. It is becoming increasingly apparent that chondrites and comets shared many similarities at the time of their formation---volatile-rich ices, organic matter and fine-grained silicates---suggesting that there may be a genetic relationship. Indeed, two dynamical models (Levison et al., 2009; Walsh et al., 2011) designed to explain the current architecture of the Solar System predict that objects that formed in the Oort and Jupiter-family comet formation regions would have been implanted primarily in the outer asteroid belt. These models suggest that the implanted outer Solar System objects are the C-complex asteroids, which are thought to be the sources of the carbonaceous chondrites, while asteroids that formed in the inner Solar System belong to the S-complex that are the sources of the ordinary, Rumaruti and enstatite chondrites. At present, the only way to test these models is through the comparison of H isotopes in cometary and chondritic water. The H isotopic compositions of water in carbonaceous chondrites indicate that they did not form in the source regions of the measured comets. Nor is there H isotopic evidence for the massive influx of water ice from the outer Solar System invoked to explain the O isotopic composition of the inner Solar System (Lyons and Young, 2005; Yurimoto and Kuramoto, 2004). Finally, bulk H and N isotopic compositions suggest that the principal source of the Earths' volatiles were probably CI chondrite-like objects, accompanied by some solar-composition material, rather than Jupiter-family comets (Hartogh et al., 2011).

Kuiper Space Sciences: Room 308
3:30 pm