Category Archives: UMD

University of Maryland geology department

UMD Geology: Lewis (JHU) on Mars rover geology

2017 Geology Colloquium Series

Friday, February 24th 2017 at 3:00 pm
in PLS 1140

Kevin Lewis
Johns Hopkins University

Exploration of Gale Crater Mars with the Curiosity Mars Rover

The Curiosity Mars rover has been exploring its landing site at Gale crater since 2012. Over this time it has begun to climb the lower slopes of Mount Sharp, a 5 kilometer high mound of sedimentary rock located within the crater. In this talk, we will combine orbital and rover-based geological and geophysical tools to understand the formation of Mount Sharp, with potential implications for other crater-hosted mounds found commonly in the Martian equatorial region. The ultimate goal of this work, and one of the key objectives of the Curiosity mission, is to understand the climate information recorded in the strata of Mount sharp exposed along the rover traverse.

UMD Geology: Pratt on Coastal Plain strata in earthquakes

2017 Geology Colloquium Series

Friday, February 3rd 2017 at 3:00 pm
in PLS 1140

Tom Pratt
USGS-Reston

The influence of eastern U.S. Atlantic Coastal Plain strata on earthquake ground motions, and damage in Washington, DC, during the 2011 Mineral, Virginia, Earthquake

During the 2011 Mw5.8 Mineral, VA earthquake, many buildings in Washington, DC, including national landmarks like the Washington National Cathedral, the Smithsonian “Castle,” and the Washington Monument, sustained damage despite being 130 km from the epicenter. The surprisingly large amount of damage from weak ground motions raises questions of how much the southeast-thickening sedimentary strata of the Atlantic Coastal Plain (ACP) strata beneath the city amplify and trap seismic energy. Partially consolidated ACP marine sedimentary strata overlie crystalline or indurated sedimentary rocks throughout coastal regions of the eastern U.S., extending more than 200 km inland from the coast. The strata taper landward from as much as 1 km near the coast to pinching out in the Washington, DC area. Shallow sedimentary strata are known to amplify earthquake ground motions due to low seismic impedance and strong reverberations. Between November 2! 014 and August 2015, we used 27 seismometers to measure ground motions across Washington, DC, using four sites on crystalline rocks as reference sites. We also used data from continental-scale seismic experiments that span the ACP to examine the influence of the broader ACP strata on earthquake ground motions. Recordings of teleseisms and regional earthquakes provided data with sufficiently high signal-to-noise for computing amplitude ratios relative to the bedrock sites. Amplifications of 10 or greater are found in the Washington, DC area due to the ACP strata, with the peak amplifications occurring near the estimated resonant frequencies of buildings throughout the city. Amplitudes decrease as the strata thicken, but even coastal sites on 600 m of ACP strata show amplification factors as great as 5. We use the frequency of the resonance peaks to invert for an average velocity function within the ACP strata. This work indicates that amplification of short-period ground mot! ions by thin ACP strata contributed to the damage in Washington, DC, d uring the 2011 earthquake, and documents longer-period amplifications that could affect larger structures beneath coastal regions of the eastern U.S. during earthquakes.

UMD: Arevalo on planetary mass spectrometry

University of Maryland 2016 Geology Colloquium Series

Friday, November 18th 2016 at 3:00 pm
in PLS 1140

Ricardo Arevalo
NASA-GSFC

Planetary Exploration and the role of in situ mass spectrometry

Top-priority science questions drive the course of NASA (and ESA) mission selection, and are defined openly by groups of scientists, engineers and planetary advocates. As the ambitions of the community evolve, so do the technologies required to address them. For decades, mass spectrometers have served as low-risk, cost-efficient means to explore the inner and outer reaches of the solar system. Legacy analyzers have characterized a range of planetary environments, including the lunar exosphere, the surface of Mars, and the atmospheres of Venus, Mars and outer planets. However, the collection of complicated mass spectra and detection of organic compounds on Mars and Titan, coupled with ground-based measurements of organics observed in meteorites and cometary materials, has underlined the importance of molecular disambiguation in next generation instruments. In response to these demands, next generation mass spectrometers promise: compatibility with ! chemical separation techniques, such as two-step ionization methods and liquid or gas chromatography; isolation/enrichment of targeted ion signals and intentional fragmentation of precursor (or “parent”) molecules; and, intrinsically higher mass resolving powers to distinguish compounds with nearly identical mass-to-charge ratios.

Here, a review is provided on the process by which missions concepts are formulated, and the evolution of mass spectrometry as a versatile analytical tool for probing the chemical compositions of high-priority planetary environments.

UMD Geology: van Keken on computational geodynamics

2016 Geology Colloquium Series

Friday, November 11th 2016 at 3:00 pm
in PLS 1140

Peter van Keken
Carnegie Institution for Science

A computational geodynamicist’s journey through the Earth in three acts: chemical geodynamics, mantle plumes and subduction zones.

“Planets in a bottle” – JHU’s Hörst @ UMD

2016 UMD Geology Colloquium Series

Friday, November 4th 2016 at 3:00 pm
in PLS 1140

Sarah Hörst
Johns Hopkins University

Planets in a bottle: Exploring planetary atmospheres in the lab

From exoplanets, with their surprising lack of spectral features, to Titan and its characteristic haze layer, numerous planetary atmospheres may possess photochemically produced particles or haze. With few exceptions, we lack strong observational constraints (in situ or remote sensing) on the size, shape, density, and composition of these particles. Photochemical models, which can generally explain the observed abundances of smaller, gas phase species, are not well suited for investigations of much larger, solid phase species. Laboratory investigations of haze formation in planetary atmospheres therefore play a key role in improving our understanding of the formation and composition of haze particles. I will discuss a series of experiments aimed at improving our understanding of the physical and chemical properties of planetary atmospheric hazes on Titan and the early Earth.

UMD: Ackerson on Tuolumne quartz

2016 Geology Colloquium Series

Friday, October 14th 2016 at 3:00 pm
in PLS 1140

Mike Ackerson
Carnegie Institution for Science

Low-temperature crystallization of granites recorded in quartz from the Tuolumne Intrusive Suite

The granitic wet solidus is a curve in temperature, pressure and composition space below which silicate melt is not present. Based on the experimentally-determined solidus curves for granitic bulk compositions, it is often assumed that granitic mineral assemblages do not crystallize below ~650-700 °C. However, some experimental data indicate that hydrous peralkaline melts can exist in equilibrium with two feldspars and quartz to temperatures as low as 330 °C. It has yet to be demonstrated whether granitic melts exist in nature to such low temperatures. Ti-in-quartz thermobarometry of granitic rocks in the Tuolumne Intrusive Suite (TIS) of the Sierra Nevada Batholith indicates that quartz in the TIS records crystallization temperatures ~122-227 °C below the commonly accepted (traditional) granodiorite wet solidus. This observation agrees with two-feldspar thermometry of the TIS and demonstrates that for some granitic systems, the tradit! ional granitic wet solidus is not the low-temperature limit of granitic magmatism.

UMD Geology: Titan’s organic aerosols

2016 University of Maryland Geology Dept. Colloquium Series

Friday, September 23rd 2016 at 3:00 pm
in PLS 1140

Melissa Trainer
NASA-GSFC

Insights on Titan’s organic aerosol formation from the laboratory

Saturn’s moon Titan is enshrouded with a thick haze that is the product of the extensive organic chemistry that takes place in Titan’s N2/CH4 atmosphere. The organic aerosol that comprises the haze has been studied extensively through observation and experimental simulations, yet the exact nature of the composition or formation mechanisms are still not known. Laboratory studies in our group have explored the optical, chemical, and isotopic properties of photochemical Titan aerosol analogs to provide insight on the major components and formation mechanism that may influence aerosol production on Titan. I will review our findings and discuss implications for improved understanding of observations of Titan’s haze as well as the chemical cycle of CH4 and trace atmospheric species.