Colloquium Schedule

Jaclyn Clark, University of Maryland, Geology

The Moon Has Its Faults

January 26, 2024 at 11:00 am (ESJ 1202)

Our Moon has an array of tectonic landforms related to contraction, orbit, and lithospheric stresses without Earth-like plate tectonics. Early studies using Apollo photography revealed that the lunar surface hosts both extensional and contractional landforms beyond those seen by Earth-based telescopes. The main types of tectonic landforms identified on the Moon are wrinkle ridges, lobate scarps, and graben. Wrinkle ridges are morphologically complex landforms in the maria, interpreted as contractional landforms resulting largely from basin subsidence. Graben are long, narrow troughs formed by extensional stresses either from subsidence or locally induced flexure. Lobate scarps are small-scale asymmetric thrust faults often located in the highlands and are the result of crustal compression mainly due to long-term interior cooling.

For over a decade, the Lunar Reconnaissance Orbiter Camera (LROC) has returned an abundance of high-resolution imagery (down to 50 cm/pixel), allowing scientists to investigate lunar tectonic landforms in greater detail and extent. Extensive mapping, modeling, and multi-dataset investigations assist in understanding the global stress state of the lunar crust. LROC data has revealed the presence of high-albedo blocks on the crest of wrinkle ridges, several or tens of meters wide craters being crosscut by ridges and scarps, and the appearance of small, 0.5-meter-deep graben near ridges and scarps. Ages determined via crater size-frequency distribution measurements indicate that our Moon has been tectonically active in the last 1 Ga, and links to shallow moonquakes recorded by Apollo seismometers suggest current tectonic activity.

Jake Shelley, Rensselaer Polytechnic Institute, Chemistry

Plasmas and Droplets and Mass Spectrometers, Oh My! New Uses for Century-Old Tools

February 9, 2024 at 11:00 am (ESJ 1202)

With the finding of evidence for liquid water on “ocean worlds,” such as Enceladus, Europa and Titan, and even frozen water on the Moon and Mars, development of instrumentation capable of detecting signs of life is an important next step. While a variety of techniques have been used for astrobiological studies on Earth and abroad, it is unlikely that one technique alone is capable of providing the necessary information to determine the presence of extant/extinct life. Rather, a number of analytical approaches capable of providing orthogonal information (often termed ‘multimodal’ analyses), will be necessary to properly characterize interplanetary oceans/ices to create a compelling case for or against the existence of extraterrestrial life as well as to gauge prospects for habitability.  The broad range of energetics offered by electrical plasmas offers the potential to provide multimodal analysis through the detection of elemental and molecular species. 

Here, we present novel approaches to provide simultaneous elemental and molecular information through the combined use of atomic emission spectroscopy (AES) and mass spectrometry (MS). In one example, a single plasma source, the solution-cathode glow discharge (SCGD), is used as an excitation and ionization source when combined with AES and MS in a single platform. The SCGD-MS/AES combination offers part-per-billion detection limits for much of the periodic table as well as small organic molecules relevant to the origins of life. In another, spatially resolved multimodal information is obtained by merging laser-induced breakdown spectroscopy (LIBS) and laser-sampling mass spectrometry. Particles from laser ablation are analysed with a plasma-based molecular ion source and MS, while AES from the laser-induced plasma (LIP) yields elemental information. Lastly, the use of electrical plasmas as chemical reactors to synthesize biologically relevant molecules in realistic early-Earth conditions will be discussed.


Eric Slessarev, Yale University, Ecology

Global geochemical thresholds and the boundaries of soil fertility

February 16, 2024 at 11:00 am (ESJ 1202)

Earth’s soils sustain productivity on land by regulating nutrient supply. In this talk I will show how two important aspects of soil fertility—soil pH and soil organic matter content—are constrained by a global-scale geochemical threshold. I will show using a global data synthesis that soil pH responds non-linearly to climate. When water inputs from precipitation are less than atmospheric water demand, base cations released by mineral weathering accumulate in soil, alkalizing soil pH. Conversely, when precipitation exceeds atmospheric water demand, base cations are lost and soil acidifies. At the abrupt transition between these two climate domains geologic inputs of base cations are a dominant control on soil pH. Using a simple process-based model, I will advance the hypothesis that elevated geologic inputs of base cations in this climatic transition zone can explain the high soil organic matter content of grassland soils. This hypothesis stands in contrast to traditional explanations for the carbon-richness of grassland soils focused on belowground allocation. These results suggest that managing soil base cation budgets could be an important tool for conserving soil fertility and carbon storage in grasslands and croplands.

Andrew Steele, Carnegie Institution for Science

Martian Organic Geochemistry - Meteorites, Curiosity and Perseverance

February 23, 2024 at 11:00 am (ESJ 1202)

Pat Megonigal, Smithsonian Environmental Research Center

Biogeochemical Mechanisms in Coastal Wetlands that Impart Greenhouse Gas Homeostasis

March 15, 2024 at 11:00 am (ESJ 1202)

Terrestrial ecosystems regulate climate by simultaneously removing and adding greenhouse gases to the atmosphere. The balance of these processes determines whether ecosystems cool or warm the planet as they respond to rising carbon dioxide, warming, novel plant species, and sea level rise. The Global Change Research Wetland is a facility at the Smithsonian Environmental Research Center dedicated to understanding plant and microbial responses to climate change using a Chesapeake Bay tidal marsh as an experimental platform. I will present examples of plant-microbe interactions that tend to cancel one another in terms of greenhouse gas emissions, effectively favoring homeostasis that neither mitigates nor contributes to ecosystem feedbacks on climate. In one example increased plant productivity led to increased microbial decomposition of soil organic matter. In the other increased plant productivity led to higher methane emissions. Such trade-offs are fundamental constraints on greenhouse gas balances that require further research to improve Earth System models.

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Alan Jay Kaufman, University of Maryland, Geology

March 29, 2024 at 11:00 am (ESJ 1202)

Andrew Knoll, Harvard University

April 5, 2024 at 11:00 am (ESJ 1202)

Maria Molina, University of Maryland, Atmospheric and Oceanic Science

April 19, 2024 at 11:00 am (ESJ 1202)

Michael Thorpe, NASA Goddard Space Flight Center

April 26, 2024 at 11:00 am (ESJ 1202)

Holly Michael, University of Delaware

May 3, 2024 at 11:00 am (ESJ 1202)

The coordinator for the Colloquium Series is Dr. Mengqiang "Mike" Zhu. You can contact him at mqzhu [at] umd [dot] edu.

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