Cool Stars 14 - Submitted Abstract # 360
This version created on 05 October 2006

Decoding Earth's spectra through its evolution


Lisa Kaltenegger, CfA
Wesley A. Traub, JPL/CfA
Kenneth W. Jucks, CfA

We have developed a characterization of the geological evolution of
the Earth's atmosphere and surface in order to model the observable
spectra of an Earth-like planet through its geological history.  These
calculations are designed to guide the interpretation of an observed
spectrum of such a planet by future instruments that will characterize
exoplanets.  Our models focus on spectral features that either imply
habitability or are required for habitability.  These features are
generated by H2O, CO2, CH4, O2, O3, N2O, and vegetation-like surface
albedos.  We chose six geological epochs to characterize.  These
epochs exhibit a wide range in abundance for these molecules, ranging
from a CO2 rich early atmosphere, to a CO2/CH4-rich atmosphere around
2 billion years ago to a present-day atmosphere.  We analyzed the
spectra to quantify the strength of each important spectral feature in
both the visible and thermal infrared spectral regions, and the
resolutions required to unambiguously observe the features for each
epoch.  We find a wide range of spectral resolutions required for
observing the different features.  For example, H2O and O3 can be
observed with relatively low resolution, while O2 and N2O require
higher resolution.  We also find that the inclusion of clouds in our
models significantly affects both the strengths and resolutions
required to observe all spectral features.  

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