Spectropolarimetry of life: airborne measurements from a hot air balloon

TL;DR

This study demonstrates the use of airborne spectropolarimetry from a hot air balloon to detect biosignatures on Earth's surface, showing potential for identifying life remotely through circular polarization measurements.

Contribution

It introduces a novel airborne spectropolarimetric method using the FlyPol instrument to distinguish biotic from abiotic features from aerial platforms.

Findings

Circular polarization spectra can differentiate biotic and abiotic features.

The FlyPol instrument achieves sensitivity of <10^{-4} in the visible spectrum.

Airborne measurements from a hot air balloon are feasible for biosignature detection.

Abstract

Does life exist outside our Solar System? A first step towards searching for life outside our Solar System is detecting life on Earth by using remote sensing applications. One powerful and unambiguous biosignature is the circular polarization resulting from the homochirality of biotic molecules and systems. We aim to investigate the possibility of identifying and characterizing life on Earth by using airborne spectropolarimetric observations from a hot air balloon during our field campaign in Switzerland, May 2022. In this work we present the optical-setup and the data obtained from aerial circular spectropolarimetric measurements of farmland, forests, lakes and urban sites. We make use of the well-calibrated FlyPol instrument that measures the fractionally induced circular polarization ($V/I$) of (reflected) light with a sensitivity of $<10^{-4}$. The instrument operates in the visible spectrum, ranging from 400 to 900 nm. We demonstrate the possibility to distinguish biotic from abiotic features using circular polarization spectra and additional broadband linear polarization information. We review the performance of our optical-setup and discuss potential improvements. This sets the requirements on how to perform future airborne spectropolarimetric measurements of the Earth's surface features from several elevations.