UWAB hosts a biannual colloquium series every spring and fall, featuring speakers from both UW and other institutions presenting on a wide range of astrobiology related topics. Here, you can find the schedule for upcoming colloquia and seminars, as well as an archive of abstracts and live recordings of past events.
Where: Physics/Astronomy Auditorium 118
When: 3 to 4 pm
*Refreshments and coffee will be served at 2:30 pm
Adrian Lenardic (Rice University)
Tectonics, Climate, and Planetary Life Potential
Volcanic and tectonic activity affects the climate evolution of terrestrial planets and, by association, the potential that a planet could maintain liquid water at its surface over geological time scales. This connects the volcanic-tectonic state of a planet to the potential that it could allow for life as we know it. As we have found more and more planets orbiting stars beyond our own, the question of what we can say about the volcanic and tectonic state of a planet, based on remote observations, has generated some interest based on its inferred link to the bigger issue of life potential within our galaxy. I will review competing ideas about what we can and, crucially from my own point of view, what we cannot say about the probable tectonic states of exo-planets given current observations. As well as bridling in some unrealistic expectations, highlighting some “limits of knowledge” can also suggest alternate modeling strategies that can be adopted under the assumption that the number of observations we have will increase*. The exercise will also isolate critical factors that have not received as much consideration as they may well merit, e.g., the potential that planets can transition between different tectonics modes over their geologically active lifetimes and the potential that the specifics of planetary formation and the early years of evolution of a terrestrial planet can cast a long time shadow (longer than has previously been assumed). Finally, I will discuss recent models of climate-tectonic coupling that explore the hypothesis that plate tectonics, as it operates on the geologically modern day Earth, may not be the only tectonic mode that allows a planet to maintain livable surface conditions over time scales that allow for biological evolution.
Yonqin Jiao (Lawrence Livermore National Laboratory)
Microbe-Mineral Interactions: Exploring the Use of Microbes for Uranium Bioremediation
Depleted uranium is a widespread environmental contaminant that poses a major threat to human health. In contrast to humans and animals where small amount of uranium can cause damage to kidneys, liver and heart, it is well known that some bacteria can tolerate high levels of uranium and influence its mobility and bioavailability in the environment. As a non-pathogenic bacterium, Caulobacter crescentus is an attractive bioremediation candidate. Our results showed that Caulobacter not only endures high concentration of uranium, but immobilizes uranium by promoting mineral precipitation, highlighting a good potential for use in uranium bioremediation. Research efforts in deciphering uranium sensing and resistance mechanisms will also be discussed.
Aki Roberge (NASA Goddard Space Flight Center)
Big Bang to Biosignatures: The LUVOIR Decadal Mission Concept
The Large UV/Optical/IR Surveyor (LUVOIR) is a concept for a highly capable, multi-wavelength observatory with ambitious science goals. This mission would enable a great leap forward in a broad range of astrophysics, from the epoch of reionization, through galaxy formation and evolution, to star and planet formation. LUVOIR also has the major goal of characterizing habitable exoplanets around Sun-like stars and searching them for signs of life.
LUVOIR is one of four Decadal Survey Mission Studies initiated in Jan 2016. The final report will be submitted to NASA and then the National Academies in 2019. Here I will summarize LUVOIR’s broad and revolutionary science goals. The study process and our current vision for the instrument suite will be explained. Finally, I’ll discuss our next steps: deciding the telescope architectures we'll study and what will happen over the next years in preparation for the 2020 Decadal Survey.
Elizabeth Bell (UCLA)
A Habitable or Hellish Early Earth? Evidence from Detrital Zircons
Although our planet is approximately 4.5 billion years old (Ga), Earth’s fossil record extends only to 3.5 Ga, the chemofossil record arguably to 3.8 Ga, and the rock record to 4.0 Ga. The first few hundred million years of Earth history has therefore long been inaccessible to most geologic investigation. In the absence of physical evidence, the early Earth was assumed to be an arid, inhospitable, and lifeless world – reflected in the name given to the period, the “Hadean.” However, in the past few decades, several localities have been discovered which contain individual grains of the mineral zircon older than 4 Ga, including abundant zircon up to nearly 4.4 Ga in age preserved in a later sandstone at Jack Hills, Western Australia. In contrast to the traditional view of Earth’s early days, various aspects of these zircons’ geochemistry suggest that a hydrosphere may have existed as early as 4.3 Ga. This new paradigm of a clement early Earth opens the possibility of a Hadean biosphere. From a population of over 10,000 zircons from the Jack Hills locality, we identified one 4.10 Ga zircon that contains primary graphite inclusions in a crack-free region, and report carbon isotopic measurements on the graphite. Evidence for carbon cycling or biologic activity can be derived from carbon isotopic studies, since a high ratio of 12C/13C is characteristic of biogenic carbon. The 12C-rich isotopic signature of these graphite inclusions is consistent with a biogenic origin and may be evidence that a terrestrial biosphere had emerged by 4.1 Ga, or ~300 million years earlier than has been previously proposed. Further investigations of the Jack Hills zircons and their Hadean carbon isotopic record may help to constrain the earliest history of life on Earth.
Jodi Young (University of Washington)
Biological CO2 Fixation and Rubisco: Evolution, Adaptation and Climate
Over 99 % of all organic carbon on Earth has been fixed from CO2 by the enzyme, Rubisco. This enzyme is found in all plants, algae, cyanobacteria and in some bacteria and archaea. Rubisco evolved nearly 3 billion years ago and its subsequent role in oxygenic photosynthesis has helped transform our planet’s atmosphere to one that is low in CO2 and high in O2. Despite Rubisco’s long history and its dominant role in autotrophic carbon fixation, it is poorly suited to fix CO2. Rubisco is big and slow, with a low affinity for CO2, and is competitively inhibited by O2 – a significant problem in a highly oxygenated world. This talk will discuss the evolutionary path of Rubisco, how it came into prominence and will discuss its role in transforming Earth’s climate. Furthermore, I will explain how Rubisco is adapted to different environments and how modern day organisms overcome Rubisco’s inherent inefficiency.
Tony del Genio (NASA Goddard Institute for Space Studies)
Habitable Planets for Humans: A Climate Modeler's Perspective
The search for habitable planets has thus far relied on a simple estimate of whether a rocky planet similar to Earth in size exists at a distance from its star that could possibly allow it to sustain surface liquid water. Eventually we may find that a few such planets actually do have water, in the atmosphere and perhaps at the surface. The question then shifts to whether these planets have detectable life. Many factors determine the answer to this question. One is the planet’s climate, which may be possible to constrain within several decades. I will discuss how 3D global climate models forced by potentially observable parameters can tell us not only the surface temperature, but whether a planet has a larger or smaller extent of habitability, by actually “following the water.” This then leads to the question: Why look for an Earth twin, if we can do better?
Victoria Meadows (University of Washington)
Proxima Centauri b: A World of Possibilities
Proxima Centauri b - a possibly terrestrial planet orbiting in the habitable zone of our Sun’s nearest stellar neighbor - will provide an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarf stars. These stars, although plentiful, undergo strong evolution in stellar brightness when they are young, and have main sequence habitable zones that are extremely close to the star. These factors enhance star-planet interactions, and could pose challenges to planetary habitability. Although Proxima Centauri b cannot be observed using current astronomical instrumentation, it may be accessible to upcoming ground-based instrumentation and telescopes, and to the James Webb Space Telescope, slated for launch in 2018. To support these upcoming observations, I will describe a comprehensive, interdisciplinary modeling study undertaken by the NAI’s Virtual Planetary Laboratory team that explores the possible evolutionary scenarios, current climate states and anticipated observational features for Proxima Centauri b - as an archetype for potentially habitable M dwarf planets. Models of stellar evolution, atmospheric escape, planetary interiors and orbital dynamics are used to generate multiple plausible evolutionary paths for Proxima Cen b, and atmospheric climate and photochemical models are then used to generate current day atmospheres and climate states. These include high-O2, high-CO2, and more Earth-like atmospheres, with either oxidizing or reducing compositions. We find that while some outcomes are indeed habitable, others may be uninhabitable due to surface temperature, desiccation, or both. We have also used radiative transfer and instrument models to generate synthetic spectra and thermal phase curves, to identify which observational features best discriminate between possible environmental states.
Paul Kintner and Steven Sholes (University of Washington) Research Rotation Presentations
Bacterial Enrichment of Laboratory Sea Ice
Paul Kintner (University of Washington)
Sea ice is an important habitat for many bacterial and algal species who survive in micrometer-scale brine-filled pockets in sea ice, an environment strongly controlled by freezing rate. Experiments have shown that algae are preferentially retained in sea ice compared to the source water; however, the enrichment of bacteria has only recently been observed in newly formed sea ice and is associated with algae. Algae-produced extracellular polysaccharide substances (EPS) are thought to serve as a mechanism for enrichment of algae into sea ice. To test bacterial enrichment in sea ice, the Cryosphere Frost Flower Reactor for Organic Geochemistry is used to freeze artificial seawater containing physchrophilic bacteria with and without EPS and at differing temperatures to mimic different freezing rates. Results suggest that bacteria are preferentially entrained in sea ice independent of EPS, but freezing rate has a strong influence. Most notably at -23 oC hydrohalite precipitates having a negative effect on bacterial enrichment, an interaction that has yet to be studied.
Improving Constraints on the Mass of Kepler-138b: a Mars Sized Exoplanet
Steven Sholes (University of Washington)
12/07/2016 (Please note this event will be on Wednesday in PAA 102 at 4 pm)
Penny Boston (NASA Astrobiology Institute)
Stealth Biospheres? Planetary Subsurfaces as Habitat and Consequences for the Search for Life
Our only current example of a biosphere is flamboyantly alive and exhibits big chemical signposts to that effect. While the search for such clearly dynamic life-bearing planets is an important target for exoplanet biosignature searches, here in our own Solar System Earth seems to be the only planet in this category. However, we harbor hopes that more cryptic biospheres may exist on other bodies, or rather within other bodies relatively close to home like Mars, Europa, or Enceladus. The living templates we have here on Earth to shape our efforts to detect such “hidden” biospheres are the subsurface microbial communities of the rock fractures of seafloors and land masses, caves, and aquifers. I will present lessons learned based on 25 years of my own team’s work in these subterrains and insights from other salient investigators. Are there ways that such cryptic biospheres might be detectable from afar?