Biology
Scientific paper
May 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agusm.a21a..02t&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #A21A-02
Biology
3367 Theoretical Modeling, 5210 Planetary Atmospheres, Clouds, And Hazes (0343), 5225 Early Environment Of Earth, 0406 Astrobiology And Extraterrestrial Materials, 0424 Biosignatures And Proxies
Scientific paper
The search for life on extrasolar planets requires first that we find terrestrial-mass planets around nearby stars, and second that we determine habitability and search for signs of life. The Terrestrial Planet Finder missions, a Coronagraph (TPF-C) and an Interferometer (TPF-I in the US, also Darwin in Europe) are designed to carry out these tasks. This talk will focus on how we could determine habitability and search for signs of life with these missions. In the visible and near-infrared, TPF-C could measure O2, H2O, O3, Rayleigh scattering, and the red-edge reflection of land planet leaves; on an early-Earth twin it also could measure CO2 and CH4. In the mid-infrared, TPF-I/Darwin could measure CO2, O3, H2O, and temperature. To validate some of these expectations, we observed Earthshine spectra in the visible and near-infrared, and modeled these spectra with our line-by-line radiative transfer code. We find that the major gas and reflection components are present in the data, and that a simple model of the Earth is adequate to represent the data, within the observational uncertainties. We determined that the Earth appears to be habitable, and also shows signs of life. However to validate the time variable features, including the continent-ocean differences, the presence of weather patterns, the large-scale variability of cloud types and altitude, and the rotation period of the planet, we need to obtain a continuous time-series of observations covering multiple rotations; these observations could be carried out in the coming years, using, for example, a site at the South Pole.
Jucks Kenneth W.
Kaltenegger Lisa
Traub Wesley A.
Turnbull Margaret C.
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