Spring 2020

Tuesdays at 3:30 PM
Natural Science Annex 101

March 31, 2020

Speaker: Jasmeet Dhaliwal, UCSC

Title: Early Planetary Evolution: Insights from Siderophile Elements

Abstract: The siderophile elements are “iron-loving,” and strongly partition into metal phases (compared to silicate phases). In early solar system materials, the siderophile elements are strongly enriched in iron meteorites and metal components of other meteorite types, while they are significantly depleted in silicate phases of meteorites. This study focuses on the highly siderophile elements and examines and contrasts their abundances in basaltic eucrite meteorites with mesosiderites, which consist of both silicate and metal phases. The highly siderophile elements are powerful tracers of early core-formation and metal-silicate differentiation in planetesimals, and lend insight into the processes that occurred on both the eucrite and mesosiderite parent bodies.


Host: Jacob Abrahams

April 7, 2020

Speaker: Andy Fisher, UCSC

Title: Subseafloor experiments and models reveal complex patterns of coupled fluid-heat-solute transport through the ocean crust


Host: Jacob Abrahams

April 14, 2020

Speaker: Paul Pearson, University of Cardiff

Title: Temperature-dependent ocean carbon cycling and evolution in the ‘twilight zone’

Abstract: Sinking of organic matter in the open ocean transfers carbon from the surface mixed layer to the ocean interior, creating a return flux of carbon from the atmosphere to the surface (the ‘biological carbon pump’). Organic matter is consumed and respired as it descends, but the rate of respiration is strongly temperature-dependent. In a warmer water column, metabolic activity is increased and the efficiency of the carbon pump tends to decline because nutrients are recycled back to the surface more quickly; conversely a cold water column has a refrigeration effect and organic matter descends further. In this presentation geological evidence for the changing efficiency of the biological pump is investigated and implications for the present and future are explored.


Host: Christina Ravelo

April 21, 2020

Speaker: Dave Stevenson, Caltech

Title: Mixing and Unmixing on Planets

Host: Francis Nimmo and Jacob Abrahams

April 28, 2020

Speaker: Ella M. Sciamma-O’Brien, NASA Ames

Title: The Ames Titan Haze Simulation (THS) experiment on COSmIC. Simulating Titan’s atmospheric chemistry and aerosol production at low temperature

Abstract: Titan, Saturn’s largest moon, is the only solid body in the outer solar system with a dense atmosphere. Because Titan’s atmosphere is mostly composed of nitrogen and methane, it is often considered as a cold primordial Earth analog. In Titan’s atmosphere, a complex chemistry occurs between N2 and CH4, its main constituents, at temperatures lower than 200K and leads to the production of heavy molecules and subsequently solid aerosols that form the haze surrounding Titan.The Titan Haze Simulation (THS) experimental setup was developed at the NASA Ames Cosmic simulation facility (COSmIC) to study Titan’s atmospheric chemistry at low temperature. The unique characteristic of the COSmIC/THS is that 1) it uses a supersonic jet expansion to cool down N2-CH4-based gas mixtures to Titan-like temperature (150 K) before inducing the chemistry by plasma discharge, and 2) the pulsed nature of the plasma allows for a controlled chemistry that is used to study the early stages of aerosol production as well as specific chemical pathways (when introducing heavier species to the N2-CH4 mixture). The COSmIC/THS plasma jet expansion accelerates the gas and solid phase products of the chemistry to supersonic speeds before they are detected and/or deposited for future analyses, hence representing the closest laboratory simulation of a probe descent in Titan’s atmosphere. Both the gas and solid phase products resulting from the plasma-induced chemistry can be monitored and analyzed using different in-situ and ex-situ diagnostics. Here, we present an overall description of the work accomplished with the COSmIC/THS in the last 10 years, our current research efforts, and the important implications for the analysis of Cassini’s returned data and preparation for future Titan missions.


Host: Xinting Yu

May 5, 2020

Speaker: Jani Radebaugh, Brigham Young University

Title: Wind-dominated landscapes of Earth, Mars, Titan and Pluto

Abstract: One of the most exciting relationships we see in comparing planetary surfaces is that wind can create remarkably similar landscapes, even in exotic materials and low-density atmospheres. Giant linear sand dunes found in Earth’s large African and Arabian deserts are identical in size, shape and behavior to linear dunes on the surface of Saturn’s moon Titan – in sand made of organics. Even in the thin atmosphere of Pluto there are dunes – in sand made of methane ice. Soft materials, such as lakebed clay, ash or methane ice at low temperatures are carved into long ridges, yardangs, by the relentless force of wind over eons, and are widespread on the surface of Mars, are found on Titan and have a unique version on Pluto. Our studies of these landscapes on Earth are revealing the conditions under which these features form and evolve on other solar system bodies.


Host: Xinting Yu

May 12, 2020

Speaker: Don DePaolo, UC Berkeley

Title: Mid-ocean ridge hydrothermal systems and the history of seawater

Abstract: The hydrothermal systems that form at mid-ocean ridge (MOR) spreading centers represent perhaps the largest and most impactful geochemical phenomenon on Earth. There is 65,000 km of MOR encircling the globe, and the flow of water through the hydrothermal systems amounts to the entire volume of the oceans every 600,000 years. As seawater circulates through the volcanic rocks of the seafloor, a large amount of heat is exchanged, but also there is chemical exchange between the oceans and the rocks. This chemical exchange affects the composition of seawater and impacts global climate. It also affects the deep mantle because the altered rocks of the oceanic crust are eventually subducted. This talk will provide an overview of these interconnections, with a specific focus on new ideas about how the chemical composition of seawater, which has changed through geologic time, might affect how the system works.


Host: Jim Zachos

May 19, 2020

Speaker: Laura Iraci, NASA Ames

Title: Using Airborne Trace Gas Measurements to Study Cities, Atmospheric Rivers, and Redwoods

Abstract: Airborne measurements of trace gases provide important contributions to understanding the Earth's atmospheric composition and processes. Measurements of the atmosphere can also tell us about the emissions and behaviors of humans and ecosystems on the surface of our planet. This talk will share results from studies by the Trace Gas Group at NASA Ames Research Center, focusing particularly on a campaign to study the Atmospheric River season of 2015-16, and a separate set of flights around Sacramento, CA, designed to quantify urban emissions of greenhouse gases. A future project over the redwood forest and offshore near Santa Cruz will also be described.


Host: Xinting Yu

May 26, 2020

Speaker: Christina Hulbe, University of Otago

Title: Calm, cool and collected: Aotearoa New Zealand's Ross Ice Shelf research programme

Abstract: The last time anybody took the measure of water circulating under the central Ross Ice Shelf, the Queen of England was celebrating her Silver Jubilee and Robert Muldoon was claiming that a hostile media cost his party votes in an election he nevertheless won. 40 years later, the Queen has gone sapphire, the third estate is complicated, and a team of Aotearoa New Zealand scientists and engineers was at 80S, 174 E, using hot water to drill through the ice shelf once again. Over 2 weeks, the interdisciplinary team observed characteristics of the ice; made repeated CTD, current, and turbulence measurements in the water under the ice shelf; sampled the water; installed an under-ice mooring; cored sea floor sediments (to 65 cm, also repeatedly); and made a suite of geophysical observations. Water properties are similar to those observed in 1977, at a site about 400 km away, but the layer structure is different. Sea floor sediments demonstrate continuous sub ice-shelf conditions since the grounding line retreated past this site, interrupted by two ice re-grounding events. This presentation will focus on the connections among ice, ocean and sea floor sediments at the site as they provide insight into ice sheet retreat since the Last Glacial Maximum as well as the nature of the sedimentary evidence itself.


June 2, 2020

Speaker: Ryan Emanuel, North Carolina State University

Title: Water in the Lumbee World: Indigenous Rights, Environmental Justice, and the Atlantic Coast Pipeline


Abstract: In North Carolina, which has the largest Indigenous population east of the Mississippi River, Native American tribes continue to occupy their ancestral lands, which include blackwater streams, swamps, and coastal plain landscapes that have helped shape and inform Indigenous cultures since time immemorial. Many of these tribes are not federally recognized and lack cultural and environmental protections that are legally granted to federally-recognized Native nations. In recent years, efforts to permit and construct fossil fuel infrastructure have exposed the vulnerability of non-federally recognized tribes to environmental and cultural degradation - both directly via construction and operation of major infrastructure, and indirectly via climate and land use change. This seminar closely examines one such project – the 1,000-km Atlantic Coast Pipeline – from my dual perspective as a Lumbee person who is also an active researcher in the environmental sciences. I describe research that moves between academic, tribal, and regulatory spaces, always with the goal of amplifying Indigenous perspectives and promoting participation of Tribal nations in environmental governance. In doing so, I hope to enrich not only public discourse but also discourse among scientists on social justice, human rights, and the complex relationship between humans and the environment.

Host: Margaret Zimmer