Category Archives: UMD

University of Maryland geology department

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.

Marcia McNutt at UMD geology dept. seminar Friday

University of Maryland Geology Department 2015 Geology Colloquium Series

Friday, December 4th 2015 at 3:00 pm
in PLS 1140

Marcia McNutt
American Association for the Advancement of Science

Can We Geoengineer Our Way Out of Climate Change? Not Likely

UMD Geology: Buffett on the origins of Earth’s magneit field

2015 Geology Colloquium Series
Friday, September 18th 2015 at 3:00 pm
in PLS 1140
Bruce Buffett
University of California, Berkeley
Geomagnetic reversals and excursions: Insights into the origins of Earth’s magnetic field
Palaeomagnetic observations offer important insights into the origin of Earth’s interior, but a detailed reconstruction of the underlying dynamics is not feasible. A practical alternative is to construct a stochastic model for the time evolution of the dipole field. Slow changes in the field are described by a deterministic (drift) term, whereas short-time fluctuations are represented by a random (noise) term. Estimates for the drift and noise terms can be recovered from a time series of variations in the axial dipole moment over the past 2 million years. The results are used to predict a number of statistical properties of the palaeomagnetic field, including the average rates of magnetic reversals and excursions. A physical interpretation of the stochastic models suggests that reversals and excursions are part of a continuum of time variations in Earth’s magnetic field, arising from convective fluctuations in the core. Relatively modest changes t! he amplitude of convective fluctuations can produce large changes in reversal rates, including the well-known occurrence of superchrons lasting longer than 10 million years.