Biology
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21734904s&link_type=abstract
American Astronomical Society, AAS Meeting #217, #349.04; Bulletin of the American Astronomical Society, Vol. 43, 2011
Biology
Scientific paper
In 2008 and 2009, the EPOXI Discovery Mission of Opportunity re-used the Deep Impact flyby spacecraft to obtain observations of the distant Earth. These spatially- and temporally-resolved visible photometric and moderate-resolution near-infrared spectroscopic observations were taken from vantage points above the Earth's Equator, and the North and South Poles. We have used the NASA Astrobiology Institute's Virtual Planet Laboratory 3-D line-by-line, multiple-scattering Earth model to simulate light curves and spectra for comparison with the EPOXI data. We used this data/model comparison to validate the Earth model for the polar regions, and to explore detectable differences in light curve amplitude, color, atmospheric effects, surface temperature and compositional differences between the poles and the equator. We explore observational differences between a planet that is covered in clouds, and one that is ice-covered, through analysis of multi-wavelength variations in time-averaged light curve amplitude. Although the equatorial view of a Snowball Earth has a large ice surface fraction, as does a modern-day Earth that is viewed from above the pole of the planet, there are discernible differences in globally-averaged surface area between the two planetary conditions, as expressed by variations in light-curve amplitude over a 24-hour rotation period. We are able to quantify the amount of radiation that various surface types contribute to the overall measured intensity of an Earth-like planetary surface as a function of illumination geometry. This has implications for future exoplanet missions, which expect to identify Earth-like planets at different evolutionary phases and viewing geometries. This work was made possible by funding from the Virtual Planetary Laboratory, a NASA Astrobiology Institute Lead Team.
A'Hearn Michael F.
Barry Richard K.
Charbonneau David
Crisp Dave
Deming Drake
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