2009 Annual Science Report

VPL at University of Washington Reporting  |  JUL 2008 – AUG 2009

Executive Summary

The Virtual Planetary Laboratory

Introduction

The Virtual Planetary Laboratory is an interdisciplinary research effort focused on answering a single key question in astrobiology: If we were to find a terrestrial planet orbiting a distant star, how would we go about recognizing signs of habitability and life on this planet?
This question is relevant to Astrobiology Roadmap Goals 1 and 7, and specifically Objectives 1.1 (Formation and Evolution of Habitable Planets), 1.2 (Indirect and Direct Observations of Extrasolar Habitable Planets) and 7.2 (Biosignatures to be Sought in Nearby Planetary Systems). This research provides a scientific foundation for interpretation of Kepler results, and for NASA’s Terrestrial Planet Finder mission concept.

While this science focus was developed prior to the detection of extrasolar terrestrial planets, subsequent observations have brought us much closer to this goal. Radial velocity surveys, initially only sensitive to planets larger than ... Continue reading.

Field Sites
34 Institutions
18 Project Reports
96 Publications
3 Field Sites

Project Reports

  • Detectability of Biosignatures

    This goal of this project is to study our ability to remotely detect life on planets. Primarily, this applies to extrasolar planets – those that exist outside our solar system. The way we will search for life on these planets is by attempting to detect gases produced by life. For example, we could detect the life on modern-day Earth if we detected gases the presence of molecular oxygen (O2, the gas we breathe that is produced by plants and bacteria) and methane (CH4, which is produced by bacteria). These two gases can co-exist only with production rates so high that they are unsustainable without the presence of life on the planet.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 6.2
  • Understanding the Early Mars Environment

    The surface of Mars today is a cold dry desert on which liquid water cannot exist. Evidence from rovers and orbiters indicate that liquid water may have existed on the surface of Mars in the distant past. This project aims to understand how it could have been warm enough for liquid water by creating computer models of the ancient Mars surface, atmosphere, and climate, and comparing the results with the available data. In a nutshell, we are trying to warm up a computer version of Mars, which is not as easy as it sounds.

    ROADMAP OBJECTIVES: 1.1 2.1
  • Astronomical Observations of Planetary Atmospheres and Exoplanets

    This task focuses on what we can learn about planets in our Solar System and exoplanets using astronomical remote-sensing techniques. These techniques include radial velocity, secondary eclipse and, for planets in our own Solar System, direct spectroscopy. These astronomical observations both tell us more about the universe, and allow us to test retrieval and observing techniques that may one day be used on extrasolar terrestrial planets.

    ROADMAP OBJECTIVES: 1.2 2.2
  • Postdoctoral Fellow Report: Mark Claire

    I am interested in how biological gases affect the atmosphere of Earth (and possibly other planets.) Specifically, I use computer models to investigate how biogenic sulfur gases might build up in a planetary atmosphere, and if this would lead to observable traces in Earth’s rock record or in the atmospheres of planets around other stars. I’m also working on how anaerobic oxidizers of methane affected the rise of oxygen on Earth, and if evolutionary changes in nitrogen-using bacteria may have changed global N2 levels and planetary climate.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 7.2
  • Planetary Surface and Interior Models and SuperEarths

    In this project, we model the processes that continually reshape the interiors and the surfaces of terrestrial (rocky) planets. The models we develop and use give us insight into how these processes (e.g. weathering, volcanism, and plate tectonics) affect a planet’s habitability as the planet evolves. In addition to Earth- and Mars-like planets, we now seek to model two sorts of planets not observed in our Solar System: 1) “super-Earths” (rocky planets up to 10 times as massive as Earth) and 2) planets so close to their star that the tides actually heat the interior of the planet.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 5.2 6.1
  • VPL Databases, Model Interfaces and the Community Tool

    The Virtual Planetary Laboratory develops modeling tools and provides a collaborative framework for scientists from many disciplines to coordinate research on the environments of extrasolar planets. As part of this framework, the VPL acts as a central repository for planetary models and the inputs required to generate those results. Developing a comprehensive storehouse of input data for computer simulations is key to successful collaboration and comparison of the models. As part of the on-going VPL Community Tools, we have are developing a comprehensive database of molecular, stellar, pigment, and mineral spectra useful in developing extrasolar planet climate models and interpreting the results of NASAs current and future planet-finding missions. The result, called the Virtual Planetary Spectral Library, will provide a common source of input data for modelers and a single source of comparison data for observers.

    ROADMAP OBJECTIVES: 1.1 1.2
  • Hydrodynamic Escape From Planetary Atmospheres

    We use computer models to simulate the behavior of the upper atmospheres of different planets (Earth, Venus, Mars, Earth-like exoplanets, etc.) during their early evolutionary stages. Young stars produce more flares and other stellar activity than older stars, and the young Sun emitted a greater amount of energetic photons than it does today, which heated the upper atmospheres of the planets. This atmospheric heating led to fast atmosphere escape, which probably controlled the atmospheric composition of early planets. The atmospheric composition on early Earth provides critical constraints on the origin and early evolution of life on this planet. The atmospheric composition of other planets provide important constraints on their habitability.

    ROADMAP OBJECTIVES: 1.1 2.1 3.1
  • Stromatolites in the Desert: Analogs to Other Worlds

    Cuatro Cienegas Basin, a desert oasis in the Chihuahua desert of central Mexico, provides a proxy for an earlier time in Earth’s history when microbes dominated the scenery. The basin hosts active, growing stomatolites, communities of microbes that are covered in carbonates, principally through the action of metabolic processes within the community. Researchers from several NAI teams are actively researching and creating experimental procedures to understand small scale and large scale evolution within these communities, using tools from biology, geology, and astronomy.

    ROADMAP OBJECTIVES: 4.1 4.2 5.2 5.3 6.1 6.2
  • Thermodynamic Efficiency of Electron-Transfer Reactions in the Chlorophyll D-Containing Cyanobacterium, Acharyochloris Marina

    Photosynthesis is the only known process that produces planetary-scale biosignatures – atmospheric oxygen and the color of photosynthetic pigments — and it is expected to be successful on habitable extrasolar planets as well, due to the ubiquity of starlight as an energy source. How might photosynthetic pigments adapt to alternative environments? Could oxygenic photosynthesis occur at much longer wavelengths than the red? This project is approaching these questions by studying a recently discovered cyanobacterium, Acaryochloris marina, which performs oxygenic photosynthesis in environments depleted in visible light but enriched in far-red/near-infrared light. A. marina is the only known organism to have chlorophyll d (Chl d) to use photons in the far-red and near-infrared, whereas all other oxygenic photosynthetic organisms use chlorophyll a (Chl a) to utilize red photons. Whether A. marina is operating more efficiently or less than Chl a-utilizing organisms will indicate what wavelengths are the ultimate limit for oxygenic photosynthesis. We have been conducting lab measurements of energy storage in whole A. marina cells using pulsed, time-resolved photoacoustics (PTRPA, or PA), a laser technique that allows us to control the wavelength, amount, and timing of energy received by a sample of cells.

    ROADMAP OBJECTIVES: 3.2 4.2 5.1 5.3 6.2 7.2
  • The VPL Life Modules

    The Life Modules of the VPL are concerned with the modeling of biosphere processes for coupling with the VPL’s atmospheric and planetary models. These coupled models enable simulation of the impact of biogenic gases on atmospheric composition, of biota on the surface energy balance, and of the detectability of these in planetary spectra. The Life Modules team has engaged in previous work coupling 1D models in the VPL’s suite of planetary models, and current work now focuses on biosphere models coupled to 3D general circulation models (GCMs). Current project areas are: 1) development of a model of land-based ecosystem dynamics suitable for coupling with GCMs and generalizable for alternative planetary parameters, and 2) coupling of an ocean biogeochemistry model to GCMs.

    ROADMAP OBJECTIVES: 1.2 6.1 6.2 7.2
  • Limits of Habitability

    The study of planetary habitability necessitates an interdisciplinary approach. The factors that can affect the habitability of planetary environments are numerous, and the disciplines that can contribute to their investigation and interpretation include, physics, chemistry, geology, biology, and astronomy to name a few.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 4.3 6.2
  • Postdoctoral Fellow Report: Steven Mielke

    This project seeks to resolve the long-wavelength limit of oxygenic photosynthesis in order to constrain the range of extrasolar environments in which spectral signatures of biogenic oxygen might be found, and thereby guide future planet detecting and characterizing observatories.

    ROADMAP OBJECTIVES: 5.1 6.1 6.2 7.2
  • Stellar Effects on Planetary Habitability

    Habitable environments are most likely to exist in close proximity to a star, and hence a detailed and comprehensive understanding of the effect of the star on planetary habitability is crucial in the pursuit of an inhabited world. We model how stars with different masses, temperatures and flare activity affect the habitability of planets. We also address the effect that tides between a star and a planet have on planetary habitability, including the power to turn potentially habitable planets like Earth into extremely volcanically active bodies like Io.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 4.1 4.3 5.3 6.1 7.2
  • Understanding Past Earth Environments

    This project examines the evolution of the Earth over time. This year we examined and expanded the geological record of Earth’s history, and ran models to help interpret those data. Models were also used to simulate what the early Earth would look like if viewed remotely through a telescope similar to NASA’s Terrestrial Planet Finder mission concept. We focused our efforts on the Earth as it existed in prior to and during the rise of atmospheric oxygen 2.4 billion years ago, as this was one of the most dramatic and important events in the evolution of the Earth and its inhabitants.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 4.1 4.2 4.3 5.1 5.2 5.3 6.1
  • Delivery of Volatiles to Terrestrial Planets

    Terrestrial planets are too small to trap gas from the circumstellar disk in which they formed and so must be built from solid materials (rock and ices). In this task, we explore how and when Earth, Mars and other potentially-habitable worlds accumulated water and organic carbon. The main challenge is that water and organic carbon are relatively volatile elements (compared to rock and metal). Therefore, during the period of time in which solids condensed at the current position of Earth, water and carbon would have been mainly in the gas phase. Getting these materials to earth required that inward transportation of material from further out in the disk.

    ROADMAP OBJECTIVES: 1.1 3.1 4.1 4.3
  • AbGradCon 2009

    The Astrobiology Graduate Student Conference (AbGradCon) was held on the UW campus July 17 – 20 2009. AbGradCon supports NAI’s mission to carry out, support and catalyze collaborative, interdisciplinary research, train the next generation of astrobiology researchers, provide scientific and technical leadership on astrobiology investigations for current and future space missions, and explore new approaches using modern information technology to conduct interdisciplinary and collaborative research amongst widely-distributed investigators. This was done through a diverse range of activities, ranging from formal talks and poster sessions to free time for collaboration-enabling discussions, social activities, web 2.0 conference extensions, public outreach and grant writing simulations.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 3.2 3.3 3.4 4.1 4.2 4.3 5.1 5.2 5.3 6.1 6.2 7.1 7.2
  • Earth as an Extrasolar Planet

    Earth is the only known planet that can support life on its surface, and serves as our only example of what a habitable planet looks like. This task uses distant observations of the Earth taken from spacecraft combined with a sophisticated computer model of the Earth to understand the appearance and characteristics of a habitable planet. With our model, we can generate accurate simulations of the Earth’s brightness, color and spectrum, when viewed at different time-intervals, and from different vantage points. We are using these simulations to understand how we might detect signs of an ocean on a distant planet, and to understand the limitations of surface temperature measurements when a planet has significant cloud cover.

    ROADMAP OBJECTIVES: 1.2 7.2
  • Planet Formation and Dynamical Modeling

    We examine how various formation processes may impact the potential development of an habitable world, and how subsequent orbital evolution can affect habitability. We explore these phenomena through numerical simulations that allow us to determine the compositions, orbits, and sometimes the internal properties of terrestrial in the Solar System and beyond.

    ROADMAP OBJECTIVES: 1.1 3.1 4.3