2010 Annual Science Report

VPL at University of Washington Reporting  |  SEP 2009 – AUG 2010

Executive Summary

The Virtual Planetary Laboratory

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 that planet? This question is relevant to the search for life beyond our Solar System, and the steps towards that are outlined in NASA’s Astrobiology Roadmap Goals 1 and 7. VPL research spans many of the Roadmap objectives, but is most relevant to 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).

Recent observations have brought us much closer to identifying extrasolar environments that could support life. The discovery earlier this year of the planet Gl 581g ... Continue reading.

Field Sites
31 Institutions
18 Project Reports
138 Publications
3 Field Sites

Project Reports

  • Thermodynamic Efficiency of Electron-Transfer Reactions in the Chlorophyll D-Containing Cyanobacterium, Acharyochloris Marina

    Photosynthesis produces planetary-scale biosignatures – atmospheric oxygen and the color of photosynthetic pigments. 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 using a laser technique to study the recently discovered cyanobacterium, Acaryochloris marina, which uses the chlorophyll d pigment to perform its photosynthesis at wavelengths longer than those used by the much more prevalent chlorophyll a. 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.

    ROADMAP OBJECTIVES: 3.2 4.2 5.1 5.3 6.2 7.2
  • Dynamical Effects on Planetary Habitability

    VPL explored numerous features of orbits. We showed that comets are unlikely to have produced more than 1 mass extinction event in the past 500 million years. We catalogued the fractions of habitable zones of nearby stars that are capable of supporting a habitable planet. We also participated in the discovery of two planets whose orbital planes are offset by 30 degrees.

    ROADMAP OBJECTIVES: 1.1 1.2 4.3
  • 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’ve also worked on how perchlorate formed in Earth’s Atacama desert as an attempt to explain how perchlorate formed on Mars

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 4.1 7.2
  • AbGradCon 2010

    The Astrobiology Graduate Student conference is a conference organized by astrobiology graduate students for astrobiology grad students. It provides a comfortable peer forum in which to communicate and discuss research progress and ideas.

    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
  • 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
  • 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 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, provides a common source of input data for modelers and a single source of comparison data for observers.

  • Understanding Past Earth Environments

    We study the chemical and climate evolution of the Earth as the best available proxy for what other inhabited planets might be like. A particular focus is on the “Early Earth” (formation through to the 1.6 billion years ago) which is poorly represented in the geological record but comprises half of Earth’s history. We have studied the total pressure of the Archean atmosphere (prior to 2.5 billion years ago), developed constraints on CO2 concentration, studied the oxygen and nitrogen cycles, the fractionation of sulfur isotopes and explored the effect of hazes on early Earth climate.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.2 5.1 5.2 6.1
  • 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
  • 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.

  • Stromatolites in the Desert: Analogs to Other Worlds

    In this task biologists go to field sites in Mexico to better understand the environmental effects on growth rates for freshwater stromatolites. Stromatolites are microbial mat communities that have the ability to calcify under certain conditions. They are believed to be an ancient form of life, that may have dominated the planet’s biosphere more than 2 billion years ago. Our work focuses on understanding these communities as a means of characterizing their metabolisms and gas outputs, for use in planetary models of ancient environments.

    ROADMAP OBJECTIVES: 4.1 4.2 5.2 5.3 6.1 6.2
  • 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 looked at how the Sun’s brightness would have changed with time. We also model how stars with different masses, temperatures and flare activity affect the habitability of planets, including looking at the effect of a very big flare on a planet’s atmosphere and surface. We find that a planet with an atmosphere like Earth orbiting around a cool red star is fairly well protected from UV radiation, but particles associated with the flare can produce damaging chemistry in the planetary atmosphere that severely depletes the planet’s ozone layer.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 4.1 4.3 5.3 6.1 7.2
  • Super-Earth Atmospheres

    In this task we use computer models to study aspects of the atmospheres of extrasolar super-Earths, planets that orbit other stars that are 2-10 times more massive than the Earth. Significant progress was made this year on three models, one that calculates how the atmosphere of the super-Earth is affected by radiative and particles coming from its parent star, one that calculates the surface temperature and change in atmospheric temperature with altitude for superEarth atmospheres and another that can model the synthetic spectrum of a superEarth when it passes in front of its star as seen from Earth.

    ROADMAP OBJECTIVES: 1.1 2.1 3.1
  • Formation of Terrestrial Planets

    This past year VPL has continued to explore key unknowns in our understanding of terrestrial planet formation. We have performed supercomputer simulations of the early formation of the Earth, and found that it can proceed more quickly than previously appreciated and suggests terrestrial exoplanets may be common. We also showed how the shape of belts of asteroids in the outer reaches of planetary systems, which can be directly observable, provide clues to the layout of the interior planets, which are often not observable.

    ROADMAP OBJECTIVES: 1.1 1.2 3.1 4.3
  • Delivery of Volatiles to Terrestrial Planets

    Habitable planets are too small to trap gases from the planet-forming disk. Their oceans and atmospheres must originate in the planetesimals from which the planet is built. In this task, we explore how, when, and from where Earth, Mars and habitable worlds around other stars can accumulate 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 the habitable zone requires that material from further out in the disk would be transported inward. Another challenge is that upon reaching the Earth, both large and small suffer severe heating during atmospheric entry. We also have investigated the fate of these compounds upon release into the atmosphere.

    ROADMAP OBJECTIVES: 1.1 3.1 4.1 4.3
  • Detectability of Biosignatures

    In this project VPL team members explore the nature and detectability of biosignatures, global signs of life in the atmosphere or on the surface of a planet. Work this year focused on the build up and detectability of sulfur-based biosignatures in early Earth-like atmospheres, especially for planets orbiting stars cooler than our Sun. We also explored the potential non-biological generation of oxygen and ozone in early Earth-like atmospheres, which could result in a “false positives” for photosynthetic life. In parallel, we worked on acquiring and getting running two simulators for telescopes that will one day be able to observe and determine the properties of extrasolar terrestrial planets.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 6.2
  • Astronomical Observations of Planetary Atmospheres and Exoplanets

    This task encompasses remote-sensing observations of Solar System and extrasolar planets made by the VPL team. These observations, while providing scientific exploration in its own right, also allow us to test our planetary models and help advance techniques to retrieve information from the astronomical data that we obtain. This can include improving our understanding of the accuracy of inputs into our models, such as spectral databases. This year we made and/or analyzed observations of Venus and Titan taken by ground-based and spaceborne observatories, and improved models for extrasolar hot Jupiters.

  • Planetary Surface and Interior Models and SuperEarths

    We use computer models to simulate the evolution of the interior and the surface of real and hypothetical planets around other stars. Our goal is to work out what sorts of initial characteristics are most likely to contribute to making a planet habitable in the long run. Observations in our own Solar System show us that water and other essential materials are continuously consumed via weathering (and other processes) and must be replenished from the planet’s interior via volcanic activity to maintain a biosphere. The surface models we are developing will be used to predict how gases and other materials will be trapped through weathering over time. Our interior models are designed to predict how much and what sort of materials will come to a planet’s surface through volcanic activity throughout its history.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 5.2 6.1
  • Understanding the Early Mars Environment

    In 2009-2010, VPL’s investigations into Mars were carried out in two major themes: investigation of the how the climate and chemistry of early Mars might (or might not) allow liquid water at the surface, and follow up science to the surprising discovery of perchlorate by NASA’s 2008 Phoenix Lander. VPL determined that, contrary to previous thought, SO2 could not keep early Mars warm, due to the inevitable formation of sulfate aerosols which counteract any warming due to SO2. Investigations into the formation of perchlorate in Earth’s deserts provide clues towards potential formation of Martian perchlorate, and specific predictions were made to all for future rovers to discriminate between evaporated versus frozen perchlorate minerals.