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.
Alan Jay Kaufman, University of Maryland, Geology
The Cryogenian Emergence and Environmental Consequences of Sponge Grade Animals
March 29, 2024 at 11:00 am (ESJ 1202)
Molecular clock estimates of animal origins suggests that sponges emerged as far back as 800 million years ago, but there is currently a >100-million-year gap in the fossil record of these simple animals that represents a critical missing piece of the Neoproterozoic puzzle. Here we report newly discovered biomineralized fossils of sponge-grade animals in Ediacaran and Cryogenian carbonates of Namibia, Siberia, Australia, and Brazil. Assembling an evolutionary framework requires that poriferan antiquity be understood in terms of sponge form and function, and the emergence of suspension-feeding amid profound environmental and climatic change. Three-dimensional reconstructi on of fossils reveals morphological characters associated with early experiments in biomineralization, including silica spicules and carbonate shells, and body plans that were evolutionarily equipped for a suspension-feeding lifestyle. As ecosystem engineers that clarified the water column and allowed for greater depths of photosynthetic activity, the arrival and propagation of sponge-grade animals had the potential to drive global environmental change recorded during extremes in the Neoproterozoic carbon cycle. These simple but novel animals would link the planktic and benthic realms for the first time in Earth history and represent a sink for photosynthetically derived organic matter that likely impacted the oxidation state of the oceans and atmosphere.
Andrew Knoll, Harvard University
Systems Paleobiology
April 5, 2024 at 11:00 am (ESJ 1202)
Systems paleobiology seeks to interpret the history of life within the framework of Earth’s environmental history, using physiology as the conceptual bridge between paleontological and geochemical data sets. In some cases, physiological performance can be estimated directly and quantitatively from fossils— this is commonly the case for vascular plant remains. In other instances, statistical inferences about physiology can be made on the basis of phylogenetic relationships. Examples from research in paleobotany, marine micropaleontology, and invertebrate paleontology illustrate how observations, experiments, and models drawn from physiology and physiological ecology can link biological radiations and extinctions to both long-term environmental trajectories and transient perturbations to the Earth system. The systems approach also provides a template for evaluating the habitability of other planets, not least the ancient surface of Mars. Expanding physiological research motivated by concerns about our environmental future provides an increasing diversity of tools for understanding the relationship between Earth and life through time. The geologic record, in turn, provides critical input to research on contemporary global change.
Maria Molina, University of Maryland, Atmospheric and Oceanic Science
Machine learning for Earth system prediction and predictability
April 19, 2024 at 11:00 am (ESJ 1202)
Machine learning can be used for Earth system prediction, or to study our ability to make skillful predictions given the system's initial state or other factors, otherwise known as predictability. In traditional numerical weather prediction frameworks, we solve the governing partial differential equations starting from an initial state. This initialized prediction framework usually involves three stages: 1) generating the initial conditions of the Earth system, 2) running the mathematical representation of the system on a computer forward in time, and 3) analyzing the output and converting it into a format that is useful for end users. Machine learning can be used to improve each of these individual stages, or to circumvent the three stage framework altogether, and examples of each will be given in this seminar. More time during the seminar will be dedicated to the challenges surrounding subseasonal prediction, which focuses on lead times of three to four weeks, and how we can use machine learning to both uncover potential biases in our initialized prediction systems and how we can bias-correct them.
Michael Thorpe, NASA Goddard Space Flight Center
Source to Sink on Earth and Mars
April 26, 2024 at 11:00 am (ESJ 1202)
Sediments and sedimentary rocks record a complex history from their generation to deposition in a concept broadly termed source to sink. On Earth, sediment composition is first determined from the overall provenance, however, it evolves in the routing system from source to sink via chemical and physical weathering, sorting, mixing, and early- to late-stage diagenesis. These sedimentary processes are all over imprinted with environmental signatures like temperature and precipitation, demonstrating the utility of sediments and sedimentary rocks to provide clues to a dynamic past. Taking lessons learned from mafic terrains here on Earth, we can attempt to extend our reference frame to Mars, which preserves a rich history of sedimentary processes. For example, the Mars Science Laboratory Curiosity rover has explored over 400 m of basin-fill stratigraphy and the sedimentology, geochemistry, and mineralogy of these sedimentary rocks detail an ancient fluvio-deltaic and lacustrine environment with a complex interaction between surface and groundwaters. Now with the Mars 2020 Perseverance rover kicking off the Mars Sample Return Campaign, we are currently tasked with using our source to sink reference frame from both Earth and Mars to prepare for some of the most precious samples to return to Earth in the near future.
Holly Michael, University of Delaware
Hydrological, biological, and geochemical linkages in coastal wetlands and their response to climate change
May 3, 2024 at 11:00 am (ESJ 1202)
Ghost forests and abandoned farms are stark indicators of ecological change along world coastlines, caused by sea level rise (SLR). These changes adversely affect land use and economies, but conversely expanding coastal marshes resulting from SLR provide crucial ecosystem services such as carbon sequestration and mediate material fluxes to the ocean. Hydrologic shifts are the primary driver of change at the marsh-upland transition. We use linked groundwater-surface water models to understand the critical controls of sea level and upland hydrology on marsh zonation and migration. We show the links between hydrology and biogeochemical conditions, and tie predicted changes to carbon sequestration. This example illustrates the tight coupling between hydrology, ecology, and biogeochemistry in coastal marshes, but many questions remain about drivers and feedbacks in these complex systems with strong hydrologic transience (e.g. tides, storms), tightly coupled ecosystem and biogeochemical mosaics, and human influences that make functioning and response at the marsh-upland transition difficult to understand and predict. We introduce a recently funded NSF Critical Zone Network project designed to untangle the hydrological, ecological, geomorphological, and biogeochemical processes that are altering the functioning of the marsh-upland transition in the coastal critical zone.
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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