Earth as an Exoplanet

TL;DR

This paper explores Earth's evolving environment and how remote sensing and modeling of our planet inform the search for habitable exoplanets, emphasizing Earth as a key reference point.

Contribution

It integrates geological, biogeochemical, and remote sensing data to develop methods for detecting habitability and life signatures on exoplanets, using Earth as a model.

Findings

Earth's environment has evolved significantly over 4.5 billion years.

Remote sensing techniques applied to Earth help develop exoplanet habitability detection methods.

Simulated datasets of Earth as an exoplanet provide insights into potential biosignatures.

Abstract

Earth is the only planet known to harbor life and, as a result, the search for habitable and inhabited planets beyond the Solar System commonly focuses on analogs to our planet. However, Earth's atmosphere and surface environment have evolved substantially in the last 4.5 billion years. A combination of in situ geological and biogeochemical modeling studies of our planet have provided glimpses of environments that, while technically belonging to our Earth, are seemingly alien worlds. For modern Earth, observations from ground-based facilities, satellites, and spacecraft have yielded a rich collection of data that can be used to effectively view our planet within the context of exoplanet characterization. Application of planetary and exoplanetary remote sensing techniques to these datasets then enables the development of approaches for detecting signatures of habitability and life on other worlds. In addition, an array of models have been used to simulate exoplanet-like datasets for the distant Earth, thereby providing insights that are often complementary to those from existing observations. Understanding the myriad ways Earth has been habitable and inhabited, coupled with remote sensing approaches honed on the distant Earth, provides a key guide to recognizing potentially life-bearing environments in other planetary systems.