Earth as an Exoplanet: A Two-dimensional Alien Map

TL;DR

This paper demonstrates the feasibility of reconstructing two-dimensional surface maps of Earth-like exoplanets from single-point light curves, using Earth as a proxy, to aid future habitability assessments.

Contribution

It introduces a novel method to derive 2D surface maps from light curves without spectral assumptions, serving as a baseline for exoplanet surface characterization.

Findings

Surface features are primarily captured in the second principal component.

Cloud information is mainly contained in the first principal component.

First successful 2D surface map of Earth reconstructed from light curves.

Abstract

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.