LPI Seminar Series2015
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 Prajkta Mane (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.
- Friday, January 23, 2015 - Lecture Hall, 3:30 PM
Helge Gonnemann, Rice University
Basaltic Volcanism: Magma Transport from Asthenosphere to Surface at Hawaii
I will discuss models of magma transport between the asthenospheric melting zone and the surface at Kilauea volcano, Hawaii. The presentation will focus on (1) an idealized model to explain temporal variability in magma supply to Kilauea; (2) dynamic linkage between Kilauea and adjacent Mauna Loa volcano; (3) some dynamical aspects of lateral magma transport within Kilauea's rift zone; and (4) the dynamics of explosive eruptions, specifically Hawaiian style fire-fountaining during the 1959 Kilauea Iki eruption.
- Friday, February 6, 2015 - Lecture Hall, 3:30 PM
Kevin Lewis, Johns Hopkins University
Cyclicity in the Rock Record of Mars and the Origin of Mount Sharp
The Martian sedimentary rock record is likely one of the best archives of that planet's evolution. Understanding the history of deposition and erosion on Mars has the potential to yield unparalleled detail about its early climate and surface conditions. Determination of depositional setting for these sedimentary deposits can constrain the climate conditions under which they formed. Yet only with an understanding of the timescales over which they accumulated can we determine their relative significance to the long-term surface evolution of the planet. I will discuss a subset of the known Martian sedimentary rock deposits which contain distinctly rhythmic stratification that may record climate change induced by quasi-periodic changes in the planet's orbital parameters. These recorded cycles can be used to obtain relative ages within the sedimentary record for the first time. I will discuss implications in particular for the origin of Mount Sharp, the field site of the Curiosity rover, and one of the locations where quasi-periodic signals have been identified.
- Tuesday, March 3, 2015 - Moved to Hess Room, 3:30 PM
Dating Impact Craters: What Can Precise and Accurate Ages Teach Us?
Impacts have played a major role in the evolution of planetary bodies and asteroids in the Solar System. About 188 impact structures – large and small, old and young – are currently known on Earth. The improvements in isotopic dating methods, in addition to stratigraphic age constraints, now offer an increasingly precise and accurate set of age data for a number of impact events on our planet. In this seminar I will present a synthesis of recent findings, current challenges and open questions in terrestrial impact crater geochronology mainly based on the 40Ar/39Ar dating technique, with examples from the North American, European and Australian impact cratering record. Precise and accurate impact ages are crucial when it comes to the potential link between large meteorite impacts, mass extinctions and biodiversification events; evidence for binary asteroid impacts and multiple impact events in the geologic record; and the nature and longevity of hydrothermal activity in cooling impact craters as hosts for economic deposits and niches for microbial life.
- Friday, March 6, 2015 - Lecture Hall, 3:30 PM
Walter Kiefer, Lunar and Planetary Institute
Preservation of Isotopic Heterogeneity in a Convecting Martian Mantle
The existence of volcanic activity on Mars in the last 200 million years is demonstrated by both the low crater densities on volcanos such as Olympus Mons and by radiometric dating of the shergottite meteorites. This implies the existence of adiabatic decompression melting and thus an actively convecting mantle. On the other hand, the preservation of isotopically distinct reservoirs that formed in the first 100 million years of solar system history has been interpreted by some investigators as evidence that the martian mantle cannot be convecting. This apparent paradox can be resolved by considering the effects of geographic isolation of isotopic reservoirs and of inefficient convective mixing, which together allow geochemical reservoirs to be preserved within a convecting martian mantle.
- Wednesday, April 15, 2015 - Lecture Hall, 3:30 PM
Barry Shaulis, University of Alberta
Investigating early lunar evolution through U-Pb chronology of the Northwest Africa 773 Clan Meteorites
The Northwest Africa (NWA) 773 clan of meteorites represent some of the youngest lunar igneous rocks discovered so far. We selected four members of the NWA 773 clan of meteorites for U-Pb zircon and baddeleyite age analysis: NWA 773, NWA 3170, NWA 6950, and NWA 7007. These meteorites were selected because: 1) Constraining the timing of igneous activity that produced these lunar rocks is critical to furthering our understanding of the thermal evolution of the Moon and evaluating potential heats sources responsible for igneous activity at least 1.5 Gyrs after lunar accretion; 2) Each of the meteorites is partially or wholly comprised of one or both of the magnesian or ferroan gabbro lithologies. This is crucial to further understanding of the proposed co-magmatic origin of the lithologies. 3) Several members contain merrillite or apatite in either a breccia or gabbro lithology. Merrillite and apatite are important uranium bearing minerals for dating and can therefore be used to establish an impact and/or brecciation history of the NWA 773 clan via U-Th-Pb dating methods. A total of 50 baddeleyite grains were analyzed and yielded weighted average 207Pb-206Pb ages of 3119.4 ± 9.4 Ma for the magnesian gabbro, 3106 ± 22 Ma for the ferroan gabbro, and 3115 ± 14 Ma for the polymict breccia. These data establish a strong chronologic link between the meteorites and indicate that the magnesian and ferroan gabbro lithologies formed at similar times. This implies that they are both temporally and petrogenetically related. A single large zircon grain found in the polymict breccia of NWA 773 yielded a U-Pb concordia age of 3953 ± 16 Ma, indicating a significantly more ancient component within the breccia. A 2718 ± 44 Ma weighted average U-Pb age of apatite from the polymict breccia and magnesian gabbro lithologies is interpreted to date the brecciation event that assembled the NWA 773 clan components on the Moon.
- Friday, April 17, 2015 - Lecture Hall, 3:30 PM
David Leverington, Texas Tech University
Is Early Development of Large Volcanic Channels Typical of all Rocky Planets?
The vestiges of large volcanic channels are preserved at the surfaces of the Moon, Venus, Mercury, Mars, and Io. The largest of these systems have widths of tens of kilometers and lengths of thousands of kilometers. Component channels were incised by voluminous low-viscosity lava flows, and are the surface expressions of magmatic systems that helped to dissipate internal heat accumulated through processes of accretion, differentiation, tidal interactions, and radioactive decay. Most of the more than 200 channels on the Moon are relatively simple systems that developed in the first ~1.5 Ga of solar system history. Lunar channels have widths of up to ~5 kilometers and lengths of up to several hundred kilometers. The more than 200 channels on Venus may have developed during the most recent 1 Ga. Some Venusian systems variously have lengths of thousands of kilometers, widths of tens of kilometers, and channel forms of remarkable complexity. Ten channel systems on Mercury have lengths of up to ~160 km and widths of up to tens of kilometers, and likely developed ~3.7 Ga before present as conduits for flood lavas emplaced across adjacent lowlands. The outflow channels of Mars have lengths of up to thousands of kilometers and widths of up to tens of kilometers, and mainly formed in the first ~1.5 Ga of solar system history. These systems are interpreted by most researchers as products of large aqueous outbursts from aquifers. However, support for aqueous interpretations is weak, and it is increasingly apparent that the characteristics of Martian outflow channels closely match those expected of volcanic systems. Widespread past development of large volcanic channels on rocky bodies beyond Earth suggests the possible formation of analogous systems on the Earth during the Hadean or Archean, a time frame of heightened internal temperatures and eruption of low-viscosity magmas. More generally, the geological record of the inner solar system suggests a predisposition of all rocky planets for early incision of large volcanic channels.
- Monday, May 11, 2015 - Lecture Hall, 3:30 AM
Patricia Craig, Jet Propulsion Laboratory
Understanding the Role of Volatiles in Shaping the Martian Surface
Volatiles in the martian crust have played an important role in shaping the surface into what we observe today as seen in the presence of hydrated minerals, such as phyllosilicates and hydrated sulfates. Observations of phyllosilicates and sulfates along with laboratory experiments allows for a ground-truthing of the recent analysis and interpretation of CheMin X-ray diffraction data that has identified phyllosilicate and sulfate minerals in Gale Crater. This has implications for the role of volatiles, specifically water and sulfur, in the formation of such minerals on the surface. Understanding how these minerals formed and were subsequently altered gives vital clues to the history of aqueous conditions on the surface in Mars’ past. In collaboration with scientists at the Astromaterials Research and Exploration Science (ARES) lab at Johnson Space Center, I have been conducting experiments that investigate the effects of acid-sulfate weathering on phyllosilicates with implications for the aqueous history of Mars. In my work, I aim to further understand the global climatic transition from the Noachian to the Hesperian eras on Mars in terms of volatile content in the crust. In this presentation, I will discuss some of my laboratory experiments constraining sulfate formation on the martian surface, the implications for these formation processes on the history of water on Mars and discuss potential collaborations with scientists at ARES.
- Friday, May 29, 2015 - Lecture Hall, 3:30 PM
Simon Kattenhorn, ConocoPhillips
Subduction on Jupiter’s Moon Europa: The Case for Plate Tectonics in the Ice Shell
Jupiter’s icy moon Europa has one of the youngest planetary surfaces in the Solar System, implying rapid recycling by some mechanism. Despite ubiquitous extension and creation of new surface area at dilational bands that resemble terrestrial mid-ocean spreading zones, there is little evidence of large-scale contraction to balance the observed extension or to recycle aging terrains. We address this enigma by presenting several lines of evidence that subduction may be recycling surface material into the interior of Europa’s ice shell. Using Galileo spacecraft images, we produce a tectonic reconstruction of geologic features across a 134,000 km2 region of Europa and find, in addition to dilational band spreading, evidence for transform motions along prominent strike-slip faults, as well as the removal of approximately 20,000 km2 of the surface along a discrete tabular zone. We interpret this zone as a subduction-like convergent boundary that abruptly truncates older geological features and is flanked by potential cryolavas on the overriding ice. We propose that Europa’s ice shell has a brittle, mobile, plate-like system above convecting warmer ice. Hence, Europa may be the only Solar System body other than Earth to exhibit a system of plate tectonics. These observations are in agreement with theoretical considerations that suggested the plausibility of convection-driven plate tectonics on Europa given its interior shell viscosity, thickness, and thermal structure.
- Friday, June 5, 2015 - Lecture Hall, 3:30 PM
Christian Klimczak, University of Georgia
Tectonic Geomorphology as a Tool to Understand the Structural Geologic History of the Moon
The Moon hosts several types of large-scale tectonic landforms that are indicative of both extensional and contractional tectonic deformation. High-resolution data returned from the Lunar Reconnaissance Orbiter (LRO) and Gravity Recovery and Interior Laboratory (GRAIL) missions allow us to assess these landforms in great detail. Extensional deformation is evident as large troughs that are interpreted to be graben structures. Grabens on Earth are generally found in rift settings, but also form as surface expressions of dike intrusions. Whether or not a graben is accompanied by a dike can be determined by a detailed analysis of their tectonic geomorphology. Contractional deformation, on the other hand, is manifest as prominent ridges, the largest of which are spatially associated with mare-filled impact basins. Ridges are believed to be the surface expression of one or more shallowly dipping thrust faults, with the ridge morphology representative of the thrust fault architecture at depth. The size and geometry of the landforms correlates with the size and geometry of the tectonic structures producing the landform, and so their morphologic characterization, coupled with numerical modeling provide a detailed set of observations and interpretations for deformation in the lunar subsurface. In this talk, I will show where large-scale graben are found to be associated with dike intrusions, and where mare ridges have been produced by large thrust faults that deeply penetrate the lunar lithosphere. These results increase our understanding of the regional and global tectonic evolution of our Moon in a quantitative manner.
- Friday, June 26, 2015 - Lecture Hall, 3:30 PM
Cyrena Anne Goodrich, Planetary Science Institute
Almahata Sitta and Other Polymict Ureilites and Why They Are So Important
Almahata Sitta is the first meteorite observed to originate from an asteroid (2008 TC3) that had been tracked and studied in space before it hit Earth, providing an unprecedented opportunity to correlate properties of an asteroid with properties of the rocks derived from it. Almahata Sitta is also unique because the fallen fragments include a wide variety of different meteorite types. Approximately 70% belong to the ureilite group of achondrites, and 30% are various types of chondrites, including all major classes (ordinary, enstatite, carbonaceous, and also R-chondrites). Almahata Sitta has been classified as an anomalous polymict ureilite. However, maybe it is not so anomalous. Previously known (typical) polymict ureilites also contain a wide variety of foreign clast types. In this regard, all polymict ureilites differ from most other meteoritic breccias, in which the sole foreign clasts are CC matrix-like dark clasts. The foreign clasts in polymict ureilites represent at least 7 different parent asteroids and a wide range of chemical and isotopic environments in the early solar system. How did all these materials become mixed with fragments of ureilites in a single asteroid, and why is this process of mixing not apparent in most other meteorites? I will discuss several hypotheses and their disparate implications for early solar system processes.
- Friday, July 24, 2015 - Lecture Hall, 3:30 PM
Jonathan Craig, University of Arkansas
Thermoluminesence Analysis of Micrometer Fragments of Primitive Extraterrestrial Materials
Extraterrestrial materials such as the matrix from un-equilibrated ordinary chondrites (UOCs) and Antarctic micrometeorites (AMMs) represent some of the most primitive solar system materials and as such they retain a memory of early solar system formation processes. There are many techniques which can determine the mineralogical, petrological or compositional information about extraterrestrial materials. Few of these, however, can provide the insight into the history of a material that is possible with thermoluminescence (TL) analysis. Heretofore considered a “bulk sample” technique we have now extended its capability to include single micrometer particle analysis. In addition to the mineralogical information provided by TL analysis it is now possible to decipher the radiation and thermal history of primitive solar system materials on a scale never seen before. TL data has shown fine scale radiation and thermal heterogeneities present in all the materials analyzed to date which, when considering the close proximity of the samples to each other in the host rock, is a startling result. The data suggest that these materials contain highly localized radiation and thermal effects from galactic/solar cosmic ray exposure. Such heterogeneities at this fine scale show unique pre-compaction characteristics of the host rock that were previously hidden from the bulk analysis.
- Tuesday, August 18, 2015 - Lecture Hall, 3:30 PM
Barbara Tewksbury, Hamilton College
Polygonal Patterns and Desert Eyes: Discovery and Study of Pervasively Developed Bedrock Structures in the Western Desert of Egypt Using Freely Available High Resolution Satellite Imagery
Using high resolution satellite imagery, the NSF-funded Desert Eyes Project has discovered and studied bedrock structures that are pervasively developed over literally tens of thousands of square kilometers in the Western Desert of Egypt. That the vast majority of these structures have gone unrecognized before now is a function of 1) the remoteness and lack of topographic relief in large tracts of the Western Desert, 2) the scale and nature of the structures, and 3) the fact that the structures occur on the "Stable Platform" of Egypt, where previous workers have for the most part not gone looking for interesting bedrock structures. The fold structures are big enough in overall size (a few hundred meters across) and have such shallow dips that they are almost impossible to see from ground level given the lack of topographic relief. But, at the same time, the structures are small enough that they remained essentially "hidden" even at the highest resolution of previously available free imagery (e.g., Landsat panchromatic imagery, 15 m/pixel). With the advent of very high resolution imagery in Google Earth (1-2 m/pixel), these structures are suddenly not only spectacularly visible, but micro-topographic features are clear enough to allow significant structural analysis. Over the past five years, the Desert Eyes Project has discovered and documented the first extensive exposure to have been recognized on land of a unique class of faults known as polygonal faults (Tewksbury et al., 2014). Polygonal faults have previously been studied essentially only in marine basins using seismic data. The Project discovered and is investigating a network of hundreds of long, narrow synclines that produce a strong regional patterning in high resolution satellite images over an area of >20,000 km2 in the Western Desert and also in places east of the Nile. The syncline network developed in a narrow time window between Early Eocene deposition of the limestone’s and formation of cross-cutting faults associated with Red Sea rifting. We are currently mapping these structures over a large area in high resolution satellite imagery and have just acquired industry seismic reflection data to pair with our structural mapping. These structures do not have geometries typical of tectonic fold and fault terrains, and we are testing a variety of non-tectonic models for formation of these structures. ------- Desert Eyes is a joint US-Egypt Project funded by an NSF program designed for international collaboration and led out of the Department of Geosciences at Hamilton College in Clinton, NY..
- Friday, September 4, 2015 - Lecture Hall, 3:30 PM
Adrian Lenardic, Rice University
Plate Tectonics in Time and Space
The paleomagnetic record, available from oceanic lithosphere, shows that plate tectonics has operated relatively smoothly over the last 150-200 million years of our planets evolution. Data based records extending deeper in geologic time, although not as conclusive, do suggest that the pace of tectonics has changed over our planets geologic lifetime. The observational constraints that are currently available are consistent with the hypothesis that plate tectonics operated in a sporadic ("episodic") mode in the precambrian. Geodynamic models indicate that this type of temporal transition can occur under hotter internal conditions for the early earth (associated with greater radiogenic heating). The combined interpretation of geologic data sets and geodynamic modeling based inferences has implications for understanding: 1) The temporal pace of tectonics over our planets geologic lifetime; 2) Potential tectonic regime transitions over Earth history; and 3) The potential for plate tectonics on other terrestrial planets, both in and beyond our own solar system. I will review the pertinent data, the models that suggest the plausibility of temporal changes in the pace and/or mode or tectonics, and the implications for Earth history and comparative planetology.
- Friday, September 18, 2015 - Lecture Hall, 3:30 PM
Patricia Craig, Lunar Planetary Institute
Insights Into the Aqueous History of Mars from Acid-Sulfate Weathered Phyllosilicates
Phyllosilicates and sulfates have been identified in close spatial proximity to each other in several locations on Mars, including Gale Crater, Mawrth Vallis, and Endeavour Crater. In many cases, Ca-sulfates are identified with either Fe/Mg-phyllosilicates or Al-phyllosilicates. While several studies have shown that sulfates result from acid sulfate-weathered basalts it is possible that phyllosilicates that formed during Mars’ earlier Noachian (~ 4.1-3.7 Ga) era would have been affected by the prevailing acidic conditions in the later Hesperian (~ 3.7-3.0 Ga). Our acid-weathering experiments showed that interlayer Ca2+ weathers out first and the layered structure of the phyllosilicates (octahedral and tetrahedral layers) can remained intact. The leached Ca2+ combined with SO42- to form Ca-sulfates. This weathering process explains the observations of sulfates in close association with phyllosilicates on Mars and provides valuable insight into the aqueous and geologic history of Mars.
- Friday, October 16, 2015 - Lecture Hall, 2:30 PM
Roger Clark, Planetary Science Institute
Space Weathering on Icy Satellites in the Outer Solar System
Space weathering produces well-known optical effects in silicate minerals in the inner Solar System, for example, on the Moon. Space weathering from solar wind and UV is expected to be weaker in the outer Solar System simply because intensities are lower.However, cosmic rays from inner to outer solar system would be similar to first order. Similarly with micrometeoroid bombardment. That, combined with the much higher volatility of icy surfaces means there is the potential for space weathering on icy outer Solar System surfaces to show optical effects. The Cassini spacecraft orbiting Saturn is providing evidence for space weathering on icy bodies. The Cassini VIMS instrument has spatially mapped satellite surfaces and the rings from .35-5 microns and the UVIS instrument from 0.1 to 0.2 microns. These data have sampled a complex mixing space between H2O ice and non-ice components and they show some common spectral properties. Similarly, spectra of the icy Galilean satellites and satellites in the Uranian system have some commonality in spectral properties with those in the Saturn system.The UV absorber is spectrally similar on many surfaces. VIMS has identified CO2, H2 and trace organics in varying abundances on Saturn's satellites. We postulate that through the spatial relationships ofsome of these compounds that they are created and destroyed through space weathering effects. For example, the trapped H2 and CO2 observed by VIMS in regions with high concentrations of dark material may in part be space weathering products from the destruction of H2O and organic molecules. The dark material, particularly on Iapetus which has the highest concentration in the Saturn system, is well matched by space-weathered silicates in the .4-2.6 micron range, and the spectral shapes closely match those of the most mature lunar soils,another indicator of space weathered material.
- Thursday, October 29, 2015 - Hess Room - Special Seminar (Note Time and Location), 1:00 PM
James W. Head, Department of Geological Sciences, Brown University
The Climate History of Mars: Was the Early Mars Climate “Warm and Wet” or “Cold and Icy”?
The current and Amazonian climate of Mars is classified as hyperarid and hypothermal, but the presence of extensive valley networks, open and closed basin lakes, and distinctly different mineralogy in the earlier history of Mars all hint at a "warm and wet" climate in the Noachian. Recent climate models have great difficulty reproducing conditions for a "warm and wet" early Mars, suggesting instead "cold and icy" conditions. We examine the predicted nature of a "cold and icy" early Mars and assess whether such a climate is compatible with the geological evidence.
- Friday, November 13, 2015 - Lecture Hall, 3:30 PM
Lujendra Ojha, School of Earth and Atmospheric Sciences, Georgia Institute of Technology
Brine Flows on Mars
Determining whether liquid water exists on the Martian surface is central to understanding the hydrologic cycle and potential for extant life on Mars. Brine flows (or seeps) have been proposed to explain the formation of some narrow streaks (termed recurring slope lineae (RSL)) observed on Mars, yet direct spectroscopic evidence was missing. Analysis of spectral data from the Compact Reconnaissance Imaging Spectrometer for Mars instrument onboard the Mars Reconnaissance Orbiter provides the first spectral evidence that recurring slope lineae form as a result of contemporary water activity on Mars. In this talk, I will give a synopsis of RSL activity on Mars, and spectral detection of hydrated salts on the slopes where rsl form.