PTYS/LPL Colloquium Schedule 2010/2011

Colloquia are held in Kuiper 308 or 312, beginning at 3:45 p.m. Refreshments at 3:30 p.m. in the Kuiper Atrium.

Tuesday, Aug 31, 2010
3:30 pm — 5:00 pm
LPL Colloquium: Photochemical Aerosols: Production, Evolution, and their Role in Titan's Atmosphere
Panayotis Lavvas, Research Associate at the Lunar and Planetary Laboratory, is the scheduled speaker. Host: Caitlin Griffith

Abstract: Titan's aerosols are a result of the complex photochemistry that takes place in the satellite's atmosphere. The Voyager missions identified the main impact of aerosols in the stratosphere, but the Cassini/Huygens mission has revealed a far more complex and intriguing picture: aerosols are detected at as high altitudes as in the thermosphere, they form multiple detached layers above the stratospheric main haze layer, they extended all the way to the surface in the main haze layer, and eventually cover the satellites surface. I will present an overview of the latest observations regarding the aerosols properties as revealed by the Cassini/Huygens instruments, and furthermore discuss recent simulations for the aerosol production and evolution. These demonstrate the feedback of aerosols in the gas phase chemistry of the atmosphere, and their role in cloud formation in the lower atmosphere.
Kuiper Space Sciences: Room 308
Tuesday, Sep 7, 2010
3:30 pm — 5:00 pm
LPL Colloquium: It's a Long Way Down: Finding Faint Planets and Disks with the LBT Interferometer
Dr. Philip Hinz from Steward Observatory is the scheduled speaker.

The rapid pace of discovery for exoplanets and disks is providing as many surprises as confirmations to our picture of planet formation and system architecture. I will review the state of these observations and describe plans with the LBT Interferometer to further our understanding of exoplanet systems. LBTI will detect warm exozodiacal emission and Jupiter-like planets, and improve our understanding of planetary system formation and evolution. It is also important ground work for the planned detection of rocky, Earth-like planets. Space missions that aim to detect light 7-10 decades down need to know first what exists at 3-6 decades fainter than a star.
Kuiper Space Sciences Building: Room 308
Tuesday, Sep 14, 2010
3:30 pm — 5:00 pm
LPL Colloquium: Chondrule Formation: A New Approach to an Old Problem
Melissa Morris, Research Associate at Arizona State University, is the scheduled speaker. Host: Lon Hood.

The parent bodies of the most primitive meteorites, the chondrites, formed ~4.57 billion years ago. Chondrites are remarkable for containing calcium-rich, aluminum-rich inclusions (CAIs), the oldest solids in the Solar System, whose formation has been dated to between 4567 and 4569 Ma. Also found in abundance within all chondrites (except for CI carbonaceous chondrites) are sub-millimeter- to millimeter-sized, (mostly ferromagnesian) igneous spheres, called chondrules, from which the chondrites derive their name. Chrondrules formed, at most, ~ 2-3 million years after CAIs as melt droplets that were heated to high temperatures while they were independent, free-floating objects in the early solar nebula. After they were heated, cooled, and crystallized, chondrules were incorporated into the parent bodies from which chondrites originate. Chondrules are capable of providing incredibly detailed information about conditions in the Solar System protoplanetary disk, if the process that led to their heating, melting and recrystallization could be understood. Chondrules make up to 80% of the volume of ordinary chondrites, and it is estimated that ~ 10^24 g of chondrules exist in the asteroid belt today. It is believed that the asteroid belt has been depleted by a factor of ~ 1000, indicating that there may have been ~ 10^27 g of chondrules in the primordial asteroid belt(at least a Mars mass of rock). Such a prevalence of chondrules suggests that chondrule-forming events were widespread in the solar nebula. A process that can melt 10^27 g of rock is surely a dominant process in the solar nebula disk, and must be identified. Any mechanism advanced to explain the melting of chondrules must meet the observational constraints on their formation, especially their thermal histories. In this talk, I will discuss the constraints on chondrule formation and several proposed formation mechanisms, in particular, the most widely-accepted hypothesis: that chondrules were melted in shock waves in the protoplanetary disk. I will present several alternatives as potential sources of such shock waves. Finally, I will discuss a new, interdisciplinary approach to the problem of chondrule formation.
Kuiper Space Sciences: Room 308
Tuesday, Oct 12, 2010
3:30 pm — 5:00 pm
LPL Colloquium: Planetary Upper Atmospheres under Strong XUV Radiation
Dr. Feng Tian (Research Associate at LASP, University of Colorado) is the scheduled speaker.
Host: Roger Yelle.

Planetary Upper Atmospheres under Strong XUV Radiation

Solar system terrestrial planets were exposed to strong (10~100 times present levels) soft X-ray and EUV (XUV) radiation from the young Sun for several hundred million years after their formation. Planetary upper atmospheres expanded to several planetary radii under such XUV radiation and fast escape of major atmosphere gases occurred. The radial outflow, as a result of fast atmosphere escape, effectively controlled the energy budget and planetary upper atmospheres could no longer remain in the traditional hydrostatic regime. Thus a new regime, the hydrodynamic regime, is proposed for planetary upper atmospheres under intensive XUV radiation. The critical EUV level, beyond which the planetary upper atmosphere enters the hydrodynamic regime, depends on the composition of the atmosphere. Such a fundamental phenomenon applies to both early solar system terrestrial planets, which are no longer directly observable, and exoplanets under strong XUV radiation such as hot Jupiters (already observed) and hot super Earths (future observations).

Atmosphere escape from planets under strong XUV radiation has important consequences not only on the atmospheres of solar system terrestrial planets, but also on the habitability of exoplanets; in particular those around low mass M-type stars. In this talk we will explore the hydrodynamic planetary upper atmospheres of early Earth, Mars, and super Earths in the habitable zones of low mass M-stars, focusing on the following topics: 1) hydrogen abundance early Earth atmosphere and its impact on the origin of life; 2) early Noachian Mars atmosphere stability and early Mars climate; 3) atmosphere stability of habitable super Earths around M-stars; and 4) Earth sourced nitrogen in lunar soil and its implication on the onset time of paleomagnetism and the rise of oxygen in the Earth's atmosphere.

Kuiper Space Sciences: Room 308
Tuesday, Oct 19, 2010
3:30 pm — 5:00 pm
LPL Colloquium
Yohai Kaspi, NOAA Climate and Global Change Postdoctoral Fellow at the California Institute of Technology, is the scheduled speaker. Host: Adam Showman.

Deep winds on giant planets and the Juno mission to Jupiter

Abstract: A key question regarding the atmospheric dynamics on giant planets is how deep are the zonal winds which are observed at the cloud-level. A common assumption is that the observed cloud-level winds extend along cylinders parallel to the axis of rotation into the interior. In this talk we discuss briefly the theory leading to this assumption, but show that entropy gradients caused by the internal
convection can lead to zonal wind shear along the direction of the axis of rotation, and therefore the interior winds will be weaker than the winds at cloud level. We demonstrate this using a new 3D compressible
general circulation model. The upcoming Juno mission to Jupiter, which will perform high resolution observations of Jupiter's gravity field, is likely to give us information about the depth of the winds. We discuss how the deep winds affect the gravity harmonics, and present a new thermal-wind method from which we can infer the expected gravity harmonics as a function of the wind depth. We find that if the winds are even a few hundred km deep they should be detectable by Juno.

Kuiper Space Sciences: Room 308
Tuesday, Nov 9, 2010
3:30 pm — 5:00 pm
LPL Colloquium: Exploring the Diversity of Exoplanetary Atmospheres
Heather Knutson (Miller Fellow, UC Berkley Dept. of Astronomy) is the scheduled speaker. Host: Adam Showman.

The past decade has marked a period of great progress in our quest to
discover and characterize the properties of the planets outside of our
own solar system. Observations of transiting systems, in which the
planet periodically passes in front of and then behind its star as
seen from the earth, have given us new insight into the nature of
these unusual worlds. I will discuss ongoing efforts to understand
the diverse properties of exoplanet atmospheres, including their
compositions, temperature profiles, and global circulation patterns.
Open questions in this area include: why do some close-in planets have
dayside stratospheres, while others do not? What role does
photochemistry play in these atmospheres? How is energy transported
from the day to the night side on tidally-locked planets? Is time
variability important in these atmospheres? I will show how we are
addressing these problems using large ongoing surveys with the Spitzer
Space Telescope, and discuss prospects for characterizing the
atmospheres of smaller and more earth-like planets with current and
upcoming facilities such as the James Webb Space Telescope.
Kuiper Space Sciences: Room 308
Tuesday, Nov 30, 2010
3:30 pm — 5:00 pm
LPL Colloquium: The Origin and Chemical Evolution of Titan's Atmosphere
Ralf Kaiser, Professor at the University of Hawai'i at Manoa, is the scheduled speaker. Host: Roger Yelle.

The arrival of the Cassini-Huygens probe at Saturn’s moon Titan – the only Solar System body besides Earth and Venus with a solid surface and thick atmosphere – in 2004 opened up a new chapter in the history of Solar System exploration. Titan’s most prominent optically visible features are the aerosol-based haze layers, which give Titan its orange-brownish color. However, the underlying chemical processes, which initiate the haze formation, have been the least understood to date. This talk reviews recent laboratory studies on the role of polyacetylenes (polyynes) and (hetero) aromatic molecules like the phenyl radical, benzene, and pyridine in the formation of Titan’s organic haze layers utilizing crossed molecular beam experiments. Those investigations provide key concepts on the formation mechanisms of unsaturated hydrocarbon molecules – in particular ployynes and aromatic compounds – together with their hydrogen deficient precursors from the ‘bottom up’ in the atmosphere of Saturn’s moon Titan. A brief outline to future research directions tackling also the heterogeneous chemistry on Titan and in hydrocarbon-rich atmospheres in the outer Solar System in general will also be presented.
Kuiper Space Sciences: Room 308
Tuesday, Jan 18, 2011
3:30 pm — 5:00 pm
LPL Colloquium: Viking Landers Did Detect Organics on Mars
Dr. Rafael Navarro-Gonzalez (Research Professor at the National Autonomous University of Mexico) is the scheduled speaker. Host: Peter Smith.

The most comprehensive search for organics in the Martian soil was performed by the Viking Landers. Martian soil was subjected to a thermal volatilization process in order to vaporize and break organic molecules, and the resultant gases and volatiles were analyzed by gas chromatography–mass spectrometry. Only water at 0.1-1.0 wt% was detected with traces of chloromethane at 15 ppb in the Viking Landing site 1, and water at 0.05-1.0 wt% and carbon dioxide at 50-700 ppm with traces of dichloromethane at 0.04-40 ppb in the Viking Landing site 2. These chlorohydrocarbons were considered to be terrestrial contaminants although they had not been detected at those levels in the blank runs. Recently, perchlorate was discovered in the Martian Arctic soil by the Phoenix Lander. Here we show that when Mars-like soils from the Atacama Desert with 32±6 ppm of organic carbon are mixed with 1 wt% magnesium perchlorate and heated nearly all the organics present are decomposed to water and carbon dioxide, but a small amount are chlorinated forming 1.6 ppm of chloromethane and 0.02 ppm of dichloromethane at 500C. A chemical kinetics model was developed to predict the degree of oxidation and chlorination of organics in the Viking oven. Re-interpretation of the Viking results therefore suggests <0.1% perchlorate and 1.5-6.5 ppm organic carbon at the landing site 1, and <0.1% perchlorate and 0.7-2.6 ppm organic carbon at the landing site 2. The detection of organics on Mars is important to assess locations for future experiments to detect life itself.
Kuiper Space Sciences: Room 308
Tuesday, Feb 1, 2011
3:30 pm — 5:00 pm
LPL Colloquium: “Geological Processes on Kuiper Belt Objects”
Dr. Steven Desch, Associate Professor at Arizona State University, is the scheduled speaker.

The Despite their small sizes, low temperatures, and their general remove from other bodies, Kuiper Belt objects (KBOs) nonetheless surely experience such geological processes as small impacts that alter their surfaces, large impacts that strip their surfaces, differentiation, and also possibly cryovolcanism, in which liquid water acts as lava. Because water ice is amorphized by cosmic rays on short timescales, the presence of crystalline water ice on the surfaces of KBOs and icy satellites, inferred from reflectance spectra, indicates a renewed surface. Cryovolcanism has been suggested as the renewing agent, but I will show that ice on outer planet satellites is rapidly annealed due to localized heating by micrometeorite impacts, and KBO surfaces may be similarly annealed if dust fluxes are about 100 times greater than at 18 AU.

Despite the lack of compelling spectral evidence for it, cryovolcanism may nonetheless be common on KBOs. I will present thermal evolution models of KBOs that show that the presence of a few percent ammonia in the ice will enable partial differentiation of KBOs and effective trapping of radiogenic heat. Even KBOs as small as Charon (radius 600 km) may retain subsurface liquid today, and I discuss mechanisms by which this liquid could be brought to the surface. Finally, I discuss the likely state of the surface of the KBO Haumea when it was struck by another KBO and its surface was stripped. I discuss implications for the numbers and spectral characteristics of the objects in Haumea's collisional family.
Kuiper Space Sciences: Room 308
Thursday, Mar 3, 2011
3:30 pm — 5:00 pm
LPL Colloquium
Nathan Bridges (Applied Physics Laboratory, JHU) is the scheduled speaker.

"The Blowing Sands of Mars"

Previous images of Mars showed that bedform migration was limited or non-existent, consistent with predictions that winds of sufficient intensity to mobilize sand were rare in the low density atmosphere. A new compilation of HiRISE images shows that virtually all dark sand patches and dunes on Mars exhibit movement of a few meters per year in the form of migration of small ripples and edges of dunes and patches.
The data can be divided into three classes: 1) Bedforms that exhibit no motion, most of which are large sand ridges, 2) dune and sand patch ripples that move at rates 2-3 orders of magnitude less than ripples of comparable size on Earth, and 3) dunes which have migration rates comparable to some terrestrial dunes. These results demonstrate that Martian sand migrates under current conditions in most areas of the planet. Winds occur at greater speeds above threshold, or do so at a higher frequency, than predicted by global circulation models.
Kuiper Space Sciences: Room 308
Tuesday, Mar 29, 2011
3:30 pm — 5:00 pm
LPL Colloquium:
Dr. Fran Bagenal from the University of Colorado is the scheduled speaker.

“Is Jupiter a Colossal Comet? Will Juno Decide?”


Jupiter is a planet of superlatives: the most massive planet in the solar system, rotates the fastest, has the strongest magnetic field, and has the most massive satellite system of any planet. These unique properties lead to volcanoes on Io, and a population of energetic plasma trapped in Jupiter's strong magnetic field that provides a physical link between the satellites, particularly Io, and the planet. Intense auroral emissions are signatures of magnetospheric dynamics. This presentation provides a rough sketch of the magnetosphere of Jupiter based on previous space missions, briefly describes the current understanding and lists outstanding issues. In particular, what drives the dynamics of the magnetosphere - rotation or the solar wind? How is the magnetosphere coupled to (or decoupled from) the ionosphere? How much of the morphologies of the magnetosphere, aurora and magnetotail (that extends to the orbit of Saturn) is simply Jupiter shedding 1 ton/second of Iogenic plasma into the solar wind? We will also discuss how measurements to be made by NASA's Juno mission (August 2011 launch) will address these issues.
Kuiper Space Sciences: Room 308
Tuesday, Apr 12, 2011
3:30 pm — 5:00 pm
LPL Colloquium
Robert E. Johnson is the scheduled speaker. Dr. Johnson is the John Lloyd Newcomb Professor of Engineering Physics, University of Virginia Astronomy Department and Department of Materials Science and Engineering.

“Molecular Kinetic Modeling of Atmospheric Escape: Pluto and Titan”


Our understanding of the evolution of planetary atmospheres is being enormously enhanced by spacecraft data on objects in the outer solar system and telescopic observation of exoplanets. Cassini is orbiting in Saturn’s system, New Horizon is on its way to the Pluto-Charon system, and the MAVEN mission to study escape from Mars will be launched soon. Surprisingly, the large amount of Cassini data on the thick atmosphere of the moon Titan, instead of re-enforcing our understanding of escape, led to rates that differed by orders of magnitude. This disagreement was due to a lack of a detailed description of how escape changes in character from evaporation on a molecule by molecule basis (Jeans escape) to an organized flow (hydrodynamic escape) a process of considerable interest for the early stages of the evolution of a planet’s atmosphere and for exoplanets orbiting close to their parent star. Therefore, we carried out extensive molecular kinetic simulations of atmospheric escape and found that the transition from Jeans to hydrodynamic escape occurs over a surprisingly narrow range of the Jeans parameter which is the ratio of the gravitational energy to the thermal energy of the molecules. The results of these simulations will be described as well as applications of a molecular kinetic model to escape from Titan and a fluid/ kinetic hybrid model to escape from Pluto.
Kuiper Space Sciences: Room 308
Tuesday, Apr 19, 2011
3:30 pm — 5:00 pm
LPL Colloquium
Dr. Dante Lauretta, Lunar and Planetary Laboratory, is the scheduled speaker.

"The OSIRIS-REx Asteroid Sample Return Mission"

Asteroids are direct remnants of the original building blocks of the terrestrial planets. Carbonaceous asteroids are an important source of volatiles and organic matter to the Earth. The Space Studies Board of the US National Research Council has identified sample return from a carbonaceous asteroid as a high priority mission. OSIRIS-REx is a sample return mission currently in Phase A in the NASA New Frontiers program. OSIRIS-REx will return samples from an organic-rich asteroid of a type not available in our meteorite collections. This type of material might have seeded Earth with the organic molecules that led to life. In addition, OSIRIS-REx will provide ground truth for ground-based and space-based telescope spectra, investigate resources potentially available for humans to use in space, and help understand how to mitigate against asteroid impacts.
Kuiper Space Sciences: Room 308
Thursday, Apr 28, 2011
3:30 pm — 5:00 pm
LPL Colloquium
Dr. Brian Toon, Chairman of the Department of Atmospheric and Oceanic Sciences, University of Colorado-Boulder, is the scheduled speaker.

"What Caused the Rivers on Mars: Greenhouse Gases or Impacts?"

Since Mariner 9 took images of Martian river valleys in 1971, we have struggled to understand how they were formed. Early Mars may have had a dense atmosphere with enough greenhouse gases to have maintained a balmy, wet climate. However, to date no one has managed to construct a climate model to support this theory and the river valleys remain a mystery. Recently, a new idea has emerged suggesting that asteroid impacts may have led to the release of water from beneath Mars’ surface.
This talk will explore how impacts could create rivers and control Mars’
early climate history.
Kuiper Space Sciences: Room 308