Earth As An Exoplanet: A Two-dimensional Alien Map

(a) 2D surface map of the Earth, treated as a proxy exoplanet, constructed using the PC2 time series. The contour of the median value is given by the black line, which serves as the coastline. The regularization parameter, λ, is 10-3 for constructing this map (see Appendix b for further details). (b) Global land/ocean map of the Earth.

Resolving spatially-varying exoplanet features from single-point light curves is essential for determining whether Earth-like worlds harbor geological features and/or climate systems that influence habitability.

To evaluate the feasibility and requirements of this spatial feature resolving problem, we present an analysis of multi-wavelength single-point light curves of Earth, where it plays the role of a proxy exoplanet. Here, ~10,000 DSCOVR/EPIC frames collected over a two-year period were integrated over the Earth's disk to yield a spectrally-dependent point source and analyzed using singular value decomposition. We found that, between the two dominant principal components (PCs), the second PC contains surface-related features of the planet, while the first PC mainly includes cloud information.

We present the first two-dimensional (2D) surface map of Earth reconstructed from light curve observations without any assumptions of its spectral properties. This study serves as a baseline for reconstructing the surface features of Earth-like exoplanets in the future.

Siteng Fan, Cheng Li, Jia-Zheng Li, Stuart Bartlett, Jonathan H. Jiang, Vijay Natraj, David Crisp, Yuk L. Yung
(Submitted on 12 Aug 2019)

Comments: Accepted by ApJL, 7 pages, 4 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1908.04350 [astro-ph.EP] (or arXiv:1908.04350v1 [astro-ph.EP] for this version)
Submission history
From: Siteng Fan
[v1] Mon, 12 Aug 2019 19:29:19 UTC (1,672 KB)
https://arxiv.org/abs/1908.04350
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