加州理工学院范斯腾博士关于系外行星的学术报告

He search for life beyond Earth is one ofthe ultimate goals of planetary science. It significantly motivates thedetection and characterization of exoplanets. After decades ofastrophysical and chemical characterization of exoplanets, astrobiological characterizationis becoming increasingly important. Analysis of the detectability ofbiosignatures is thus critical. Planet Earth, the only celestial object knownto harbor life, provides the single ground truth for biosignatures. Analyzingthe light curves of Earth, treated as a proxy exoplanet, can therefore providethe baseline for analyzing the detectability and observation limit of potentialbiosignatures from exoplanets. In this talk, I will present an analysis ofmulti-wavelength single-point light curves of Earth, where it plays the role ofa proxy exoplanet, using observations obtained by the recent Deep Space ClimateObserVatoRy (DSCOVR) mission. In a preliminary  analysis, we found that,between the two dominant principal components (PCs), the second PC containssurface-related features of the planet, while the first PC mainly includescloud information. The first two-dimensional (2D) surface map of Earth istherefore reconstructed from light curve observations without any assumptionsof its spectral properties. This study serves as a baseline for reconstructingthe surface features of Earth-like exoplanets in the future.

Figure 1. Surface mapof Earth, which serves as a proxy exoplanet, reconstructed frommulti-wavelength light curves. The contour of median is denoted as the blackline. (Fan et al. 2019).