LPI Seminar Series2018
The LPI Seminar Series brings prominent scientists to the LPI to present on a broad array of scientific disciplines that advance our understanding of the solar system. The seminar series, which began in September 1969, has brought many notable contributors from numerous research and academic institutions to the LPI. Seminars are held on Thursdays from 3:30-4:30 p.m. in the Lecture Hall at USRA/LPI, 3600 Bay Area Boulevard, Houston, Texas. A map of the Clear Lake area is available here. Light refreshments are served at 4:30 p.m.
For more information, please contact Heather Meyer (phone: 281-486-2154; e-mail: firstname.lastname@example.org) or Katie Robinson (phone: 281-486-2114; e-mail: email@example.com.) The schedule is subject to revision.
See also the Rice University Department of Physics and Astronomy Colloquia and the Department of Earth Science Colloquia pages for other space science talks in the Houston area.
- Thursday, January 11, 2018 - Lecture Hall, 3:30 PM
Joshua Louis Bandfield, Space Science Institute
LPI Seminar: Understanding the global distribution and formation processes of water and hydroxyl on the Moon
Lunar infrared spectra show evidence for the presence of OH and H2O, with previous work indicating the strongest signals at high latitudes and at early and late local times. However, these spectral data need to be corrected for small amounts of thermal emission, requiring detailed modeling of lunar surface temperatures to avoid significant inaccuracies. Using an updated thermal emission and surface roughness model, the newly corrected spectral data show evidence for OH/H2O that is present at all latitudes, local times, and surface types, suggesting a much more widespread presence on the lunar surface. This distribution implies a solar wind-related process that mainly forms OH that is more tightly bound to lunar surface materials and negates the need for a dynamic migration of water across the lunar surface on diurnal timescales.
- Friday, February 9, 2018 - Lecture Hall, 3:30 PM
Ralph Lorenz, Johns Hopkins University Applied Physics Lab
LPI Seminar: Titan’s Landscape – Sand and Sea!
Titan is an outstanding world for comparative planetological studies of surface-atmosphere interaction, processes that affect us here on Earth (such as shoreline erosion by wind-generated waves at sea, or flash-flooding by large rainstorms). I review what the Cassini-Huygens mission has told us about these processes and the resulting imprints on the landscape.
- Monday, March 26, 2018 - Lecture Hall, 3:30 PM
LPI Seminar: Phase Equilibria Modeling Applied to Crustal Rocks on Earth and Mars
Phase equilibria calculations enable a better understanding of phase relations in complex metamorphic and igneous systems and a methodical study of the variation in rock properties such as densities and seismic velocities. Furthermore, the extracted rock property grids can be combined with geodynamic, geophysical and geochemical models improving our knowledge of rock and melting behavior in various tectonic environments on Earth and other terrestrial planets. This talk will cover a few scenarios, where phase equilibrium calculations are particularly useful due to their inaccessibility such as the densification of lower crustal rocks with respect to basin formation and orogenic roots, melting processes and their relevance for early crustal evolution, and low-grade metamorphism of mafic Martian rocks.
- Tuesday, April 10, 2018 - Lecture Hall, 3:30 PM
Prajkta Mane, Arizona State University
LPI Seminar: Unraveling the Early Solar System History recorded in Calcium-Aluminum-rich Inclusions
Calcium-Aluminum-rich Inclusions (CAIs) are the first-formed solids in the solar system and record some of the earliest processes that occurred in the solar nebula. These earliest-formed solids are surrounded by concentric multi-mineralic rim sequences. These rims are present around most CAIs from different types of chondrites. As such, these rims record a universal event that marks the end of the growth period of CAIs. In this talk, I will discuss results of a coordinated multi-technique approach to analyzing CAIs and their rims and revealing the timescales and conditions of their formation.
- Friday, April 13, 2018 - Lecture Hall, 3:30 PM
Duck Mittlefehldt, NASA Johnson Space Center
LPI Seminar: Asteroidal Differentiation: The Record in Achondrites, Stony Irons and Irons (a.k.a. the Cool Meteorites)
Nothing of consequence happened in the universe from the time of the Big Bang until 4.564 Gyr ago when an assortment of small bodies in our Solar System underwent igneous differentiation, some quite vigorously, over a period of only a few Myr. Then, the universe resumed it inconsequential existence. Some meteorites - achondrites, stony irons and irons - contain a record of this brief, but exciting time in the history of the universe. I will discuss the petrologic and geochemical characteristics of several groups of meteorites that help us understand the range of magmatic processes that affected asteroids.
- Friday, April 20, 2018 - Lecture Hall, 3:30 PM
Margaret Landis, University of Arizona
LPI Seminar: Contribution of Sublimating Water Ice to Ceres' Exosphere
Telescopic observations of Ceres have revealed the presence of a transient exosphere of either water vapor or its photolytic products. Observations from the Dawn mission have revealed Ceres to be an overall ice-rich world. I use temperature and vapor production models in combination with observations from Dawn in order to quantify the amount of water vapor that could be contributed to Ceres' exosphere from ground and surface ice. I also discuss the role that small impacts have had in generating exposed surface ice.
- Thursday, April 26, 2018 - Lecture Hall, 3:30 PM
Tom Lapen, University of Houston
LPI Seminar: Mantle Sources of Shergottites - New Insights from an Expanding Meteorite Record
Insights into the duration of igneous activity and the nature of magma sources in Mars have been made from analyses of shergottite meteorites – mafic to ultramafic igneous rocks from Mars’ crust. The ejection ages of martian meteorites, the sum of the cosmic ray exposure (CRE) and terrestrial residence ages, have been used to link groups of meteorites to common pre-launch locations on Mars. These spatial relationships provide insights into the timing and compositions of magmas produced from particular magmatic systems. Data compilations and some hypotheses on the nature of shergottite mantle sources will be presented.
- Thursday, May 3, 2018 - Lecture Hall, 3:30 PM
L. Ilsedore Cleeves, Harvard-Smithsonian Center for Astrophysics
LPI Seminar: Linking protoplanetary disk chemistry with exoplanetary compositions
Recent advances in sensitivity have allowed us to begin to measure and even map the compositions of gas-rich protoplanetary disks. How these compositions are imparted into newly forming planets is still an open question that draws from topics of gas motions, dust dynamics, and, of course, chemistry. I will discuss how ALMA is shedding light on each of these topics, and how these parts fit into a newly emerging (and potentially dynamic) picture of chemistry during planet formation. I will finally discuss how what we've learned from the outer disk (> 10 AU) from ALMA may influence the compositional properties of the inner terrestrial planet formation region, and how we might test such ideas with future facilities such as JWST.
- Friday, June 22, 2018 - Lecture Hall, 3:30 PM
Kirsten Siebach, Rice University
LPI Seminar: Sedimentary Records from Another World: Exploring Gale Crater with the Curiosity Rover
Since landing on the floor of Gale crater in August 2012, the Mars Science Laboratory Curiosity rover has explored over 350 m of basin-fill stratigraphy primarily consisting of fluvio-deltaic deposits and lacustrine mudstones. Curiosity's findings have revolutionized our understanding of Mars: the planet had more igneous diversity than predicted, long-lived liquid water in rivers and lakes at the surface, environments that would have been habitable for life, multiple episodes of diagenetic fluids, and multiple cycles of crater fill and erosion. I will present the developing story of the history of the Gale crater basin, and the basin analysis work I have done to understand source-to-sink processes by separating effects from source rock diversity, sediment transport, and diagenetic influences for multiple sedimentary cycles.
- Monday, July 9, 2018 - Lecture Hall, 10:00 AM
Lauren Schurmeier, University of Illinois at Chicago
LPI Seminar: Domed Labyrinth Terrains – What Can They Tell Us About Titan’s Ice Shell?
The methane in Titan’s atmosphere is constantly photochemically broken down into organic molecules that collect in hazes and sediments on the surface. This fast breakdown, along with the identification of vast organic-rich regions of Titan, including dunes, Undifferentiated Plains, and Labyrinth Terrains, implies that methane replenishment must occur. Titan’s ice shell may contribute to atmospheric methane replenishment through direct insertion due to cryovolcanic eruptions or release from near surface methane clathrates. Unfortunately, there is little direct evidence for the existence of methane clathrates, and while putative cryovolcanic constructs has been identified, the interpretation as cryovolcanoes has been debated. I study specific topographic loads in Titan’s mid-latitudes - large isolated plateaus and clustered dome shaped Labyrinth terrains - to determine if they could have cryovolcanic origins, and investigate through finite-element modeling and scaling relationships if they can form within or be supported by a water ice-rich or methane clathrate-rich ice shell. My results show that despite its greater strength relative to water ice, methane clathrate shells are too thermally insulating, resulting in thinner lithospheres that are inconsistent with these topographic loads. Thin lithospheres cannot support large plateaus; they must be supported in a predominately water ice-rich shell. Similarly, if Titan’s dome shaped Labyrinths are large subsurface cryovolcanic laccoliths that form near Titan’s brittle-ductile transition, their sizes imply a predominately ice-rich shell, not a predominately methane clathrate ice shell in the mid-latitudes. The methane that recharges Titan’s atmosphere may need to come from somewhere else.
- Wednesday, July 11, 2018 - Lecture Hall, 3:30 PM
Tabb Prissel, Rutgers University, Dept. of Earth & Planetary Sciences
LPI Seminar: Revisiting Models of Lunar Troctolite Formation
There are two types of pristine lunar troctolites as distinguished by spinel chemistry: “common” lunar troctolites +/- chromite, and the volumetrically minor pink spinel-bearing troctolites (PST). Recent experimental evidence indicates PST mineralogy is best explained by reaction between MgO-rich primary liquids and anorthite. The formation of common lunar troctolites can be attributed to equilibrium crystallization prior to reaction with anorthite. Previously, models of equilibrium crystallization were ruled out due to the pairing of forsteritic olivine with anorthitic plagioclase (i.e., the so-called “Mg# problem”). However, in this presentation I will demonstrate that equilibrium crystallization of MgO-rich primary liquids can reconcile the high forsterite content, as well as the presence of chromite, observed in common lunar troctolites. These results are then discussed in the context of a differentiating lunar magma ocean, and also the onset, duration, and global extent of cumulate mantle overturn.
- Thursday, July 12, 2018 - Lecture Hall, 3:30 PM
Terik Daly, Johns Hopkins
LPI Seminar: When impacts impart: New insights into the delivery of water by impacts
Dynamical models and observational evidence indicate that water-rich asteroids and comets deliver water to objects throughout the solar system, but the mechanisms by which this water is captured have been unclear. New experiments reveal that impact melts and breccias capture up to 30% of the water carried by carbonaceous chondrite–like projectiles under impact conditions typical of the main asteroid belt impact and the early phases of planet formation. This impactor-derived water resides in two distinct reservoirs: in impact melts and projectile survivors. Impact melt hosts the bulk of the delivered water. Entrapment of water within impact glasses and melt-bearing breccias is therefore a potential source of hydration features associated with craters on the Moon and elsewhere in the solar system and likely contributed to the early accretion of water during planet formation.
- Thursday, September 27, 2018 - Hess Room, 3:30 PM
LPI Seminar: Desiree Cotto Figueroa, University of Puerto Rico
Scale-Dependent Measurements of Meteorite Strength and the Implications for Asteroid Fragmentation
Measuring the strengths of asteroidal materials is important for developing mitigation strategies for potential Earth impactors and for understanding properties of in situ materials on asteroids during human and robotic exploration. Studies of asteroid disruption and fragmentation have typically used the strengths determined from terrestrial analog materials, although questions have been raised regarding the suitability of these materials. The few published measurements of meteorite strength are typically significantly greater than those estimated from the stratospheric breakup of meter-sized meteoroids. Given the paucity of relevant strength data, the scale-varying strength properties of meteoritic and asteroidal materials are poorly constrained. Based on our uniaxial failure studies of centimeter-sized cubes of a carbonaceous and ordinary chondrite, we develop the first Weibull failure distribution analysis of meteorites. This Weibull distribution projected to meter scales, overlaps the strengths determined from asteroidal airbursts and can be used to predict properties of to the 100 m scale. In addition, our analysis shows that meter-scale boulders on asteroids are significantly weaker than small pieces of meteorites, while large meteorites surviving on Earth are selected by attrition. Further, the common use of terrestrial analog materials to predict scale-dependent strength properties significantly overestimates the strength of meter-sized asteroidal materials and therefore is unlikely well suited for the modeling of asteroid disruption and fragmentation. Given the strength scale-dependence determined for carbonaceous and ordinary chondrite meteorites, our results suggest that boulders of similar composition on asteroids will have compressive strengths significantly less than typical terrestrial rocks
- Thursday, October 11, 2018 - Lecture Hall, 3:30 PM
Frances Rivera-Hernandez, Dartmouth College
LPI Seminar: Lakes, Rivers, and Dry Landscapes in Gale Crater, Mars: The Importance of Understanding Grain Size Variations
Reconstructing ancient depositional environments is key to accomplishing the main goal of the Mars Science Laboratory mission: to characterize habitable environments of early Mars from the sedimentary record in Gale crater with the Curiosity rover. Accurate measurement of the size and distribution of grains in sedimentary rocks is crucial for interpreting depositional environment. This is a challenging task on Mars using rover images. However, grain size can be inferred from ChemCam Laser Induced Breakdown Spectroscopy data using the Gini Index Mean Score (GIMS), a statistical measure of compositional variability. > Results using the GIMS suggest that rocks in Gale crater from the ~5.2 m thick Yellowknife Bay formation consist of mudstones overlain by poorly sorted sandstones, demonstrating that flow characteristics shifted abruptly from a low-energy lake to a high energy alluvial environment. In contrast, GIMS results suggest that the ~300-m thick Murray formation consists primarily of mudstones with intervals of fine to coarse sandstones. While the interstratified sandstones indicate rapid fluid flow either in aeolian or fluvial environments, the persistence of mudstones suggest that lakes may have been sustained in Gale crater for tens of thousands to millions of years. Early Mars must have had climatic conditions that could have sustained the diversity of depositional environments preserved in Gale Crater.
- Thursday, November 8, 2018 - Lecture Hall, 3:30 PM
Simon Lock, Harvard University
LPI Seminar: The Origin of the Moon Within a Terrestrial Synestia
The giant impact hypothesis remains the leading theory for lunar origin. However, current models struggle to explain the Moon's composition and isotopic similarity with Earth. I will present a new lunar origin model that can match the observational constraints. High‐energy, high‐angular‐momentum giant impacts can create a post‐impact structure that exceeds the corotation limit, which defines the hottest thermal state and angular momentum possible for a corotating body. In a typical super‐corotation‐limit body, traditional definitions of mantle, atmosphere, and disk are not appropriate, and the body forms a new type of planetary structure, named a synestia. Using simulations of cooling synestias combined with dynamic, thermodynamic, and geochemical calculations, we show that satellite formation from a synestia can produce the main features of our Moon. We find that cooling drives mixing of the structure, and condensation generates moonlets that orbit within the synestia, surrounded by tens of bars of bulk silicate Earth vapor. The moonlets and growing moon are heated by the vapor until the first major element (Si) begins to vaporize and buffer the temperature. Moonlets equilibrate with bulk silicate Earth vapor at the temperature of silicate vaporization and the pressure of the structure, establishing the lunar isotopic and chemical composition. Eventually, the cooling synestia recedes within the lunar orbit, terminating the main stage of lunar accretion. Our model shifts the paradigm for lunar origin from specifying a certain impact scenario to achieving a Moon‐forming synestia. Giant impacts that produce potential Moon‐forming synestias were common at the end of terrestrial planet formation.
- Friday, November 16, 2018 - Lecture Hall, 3:30 PM
Canceled - Frances Bagenal, University of Colorado
LPI Seminar: Canceled
- Friday, November 30, 2018 - Lecture Hall, 3:30 PM
Joan Schmelz, USRA / SOFIA
Infrared Astronomy in the Age of SOFIA
SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a 2.7 meter telescope carried aboard a Boeing 747 and operated by NASA. SOFIA flies above 99% of the Earth’s water vapor, providing the international astronomical community with access to the mid- and far-infrared. Imaging, spectroscopic, and polarimetric instruments investigate a variety of physical, chemical, and dynamical processes as well as the vital role of the magnetic field in diverse cosmic environments. SOFIA astronomers investigate the formation of stars and planets. Measurements of the broad spectral energy distribution of nascent massive stars constrain models of collapsing cores. Data are used to refine accretion and cooling models of circumstellar disks and to study the kinematics, composition, and evolution of disks around low‐mass young stellar objects. SOFIA studies the chemical composition of protoplanetary disks, and in particular, the gaseous and solid‐state material out of which new planets form. SOFIA explores the physical processes governing how stars interact with their environments, the origin of dust, and the role of large, complex carbon molecules — notably polycyclic aromatic hydrocarbons (PAHs). Data are used to investigate the origin of dust in the Milky Way and other galaxies. The newest instrument investigates the magnetic field in nebulas, the galactic center, and other galaxies by observing polarized light from aligned dust grains. In this talk, I will describe my five favorite SOFIA science results.
- Thursday, December 6, 2018 - Lecture Hall, 3:30 PM
Bill Stone, Stone Aerospace, Austin, TX
LPI Seminar: Ocean World and Martian Sub-ice Access and Exploration Technology: How Close Are We to Viable Flight Vehicles?
The recent discovery of a possible (as-yet unverified) subglacial lake beneath the south pole ice cap of Mars has increased interest in reaching such places with robotic technology. During the past decade research has been conducted on ice penetrating “cryobots” and cryobot-deployed autonomous underwater vehicles (AUV) in preparation for sub-surface missions to Ocean Worlds. This talk will provide an overview of the current state of ice penetrating and sub-ice exploration technology that is being developed towards flight missions. Of primary importance is a nuclear power source, which can be optimized for cryobot operations. In addition, there are five cryobot operating regimes (starting, brittle ice transit, ductile ice transit, obstacle avoidance/passage, and breakthrough into voids or ocean). Each of these presents unique challenges to and constraints on a vehicle. Currently, four penetrator technologies have been identified that can be used either singly or collectively: passive thermal melt probes, closed-cycle hot water drills (CCHWD), laser penetration, and mechanical drills. All are currently being advanced in the NASA COLDTech program as each has certain tradeoffs. Mechanical drills have been shown to work in cold ice and are able to penetrate non-ice solids, but suffer from wear and binding. Lasers are extremely efficient in cutting through cold and warm ice, including in vacuum conditions, but require large amounts of electrical power. CCHWD systems can also cut through debris-laden ice and steer to avoid obstacles. In this presentation, we discuss pros and cons of each of these penetrator technologies in light of new nuclear power sources. We also discuss constraints on deployable sub-ice swimming rovers necessary to expand exploration radius from an initial breakthrough point into a sub-surface water body as well as the state of AI operating behaviors for such rovers that dramatically enhance autonomous exploration capabilities. Finally, we propose several new test facilities that will both advance these technologies to flight readiness and improve our understanding of Earth’s and extraterrestrial cryospheres.