# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1908.04350