HR: 11:20h
AN: SA52A-05 INVITED     [Abstracts]
TI: Understanding the Signatures of Life in Disk-averaged Planetary Spectra
AU: Meadows, V S
EM: vsm@ipac.caltech.edu
AF: Infared Processing and Analysis Center/Calfornia Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 United States
AU: * Tinetti, G
EM: tinetti@ipac.caltech.edu
AF: Infared Processing and Analysis Center/Calfornia Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 United States
AU: Segura, A
EM: antigona@ipac.caltech.edu
AF: Infared Processing and Analysis Center/Calfornia Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 United States
AU: Crisp, D
EM: David.Crisp@jpl.nasa.gov
AF: Jet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Kasting, J F
EM: kasting@geosc.psu.edu
AF: Pennsylvania State University, 443 Deike Building University Park, State College, PA 16802 United States
AU: Kiang, N
EM: nkiang@giss.nasa.gov
AF: Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 United States
AU: Velusamy, T
EM: Thangasamy.Velusamy@jpl.nasa.gov
AF: Jet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AB: NASA and ESA are currently supporting the multi-decadal development of a suite of missions to directly detect and characterize terrestrial planets around other stars. The first of these missions is slated for launch as early as 2015, and will provide our first opportunity to spectroscopically study the global characteristics of Earth-like planets beyond our solar system, to search for signs of habitability and life. These missions will allow us to explore the diversity of terrestrial planets around stars of different spectral type, and as our neighboring stars have ages from newborn to 10Gy old, may also allow us to observe terrestrial planets at different stages of planetary and ecosystem evolution. However, these missions will not provide spatial resolution across the visible planetary disk, and the planet's surface and atmospheric composition, physical properties, and the presence of life, must all be inferred from a disk-averaged spectrum. Until these missions fly, we must use observations of the Earth, geological constraints, and planetary environment and radiative-transfer models to understand the global characteristics of a planet that indicate its potential habitability, or the likely presence of life, at each stage in its evolutionary development. We must also determine the probability that these biosignatures will be detectable in disk-averaged spectra at low spectral resolution, and that we will characterize the planetary environment sufficiently to identify the biosignature in context, and any planetary characteristics that may provide "false positives" for life. The Earth exhibits abundant O₂ in its atmosphere, and the spectral features O₂, O₄ and O₃ in its disk-averaged spectrum provide strong signposts for life. Although less detectable for the modern day Earth, the presence of biogenically produced compounds such as CH₄, N₂O, and CH₃Cl, in the context of the environment in which they are detected, may also be indicators of life. Additionally, this presentation will show that these compounds may be more detectable in an Earth-like atmosphere around stars of different spectral type (Segura et al., 2003) or at earlier stages of the Earth's planetary history. Surface biosignatures may also be present. On the Earth, the characteristic rise in the reflectivity of land vegetation longward of 0.7μm, the "red-edge", is visible from space, and our recent results show that it may even be detectable in the disk-averaged spectrum, although its relatively detectability is necessarily a function of cloud-cover and planetary phase.
DE: 0424 Biosignatures and proxies
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 5210 Planetary atmospheres, clouds, and hazes (0343)
DE: 5225 Early environment of Earth
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005