Biosignatures of the Earth

Biosignatures of the Earth: I. Airborne spectropolarimetric detection of photosynthetic life

Patty, C. H.Lucas (University of Bern)
Kühn, Jonas G. (University of Bern; Université de Genève)
Lambrev, Petar H. (Biological Research Center)
Spadaccia, Stefano (University of Bern)
Keller, C.U. (TU Delft QN/Fysics of NanoElectronics; Universiteit Leiden)
Mulder, W. (TU Delft Astrodynamics & Space Missions; Universiteit Leiden)
Pallichadath, V. (TU Delft Astrodynamics & Space Missions)
Snik, Frans (Universiteit Leiden)
Stam, D.M. (TU Delft Astrodynamics & Space Missions)

2021

Context. Homochirality is a generic and unique property of life on Earth and is considered a universal and agnostic biosignature. Homochirality induces fractional circular polarization in the incident light that it reflects. Because this circularly polarized light can be sensed remotely, it can be one of the most compelling candidate biosignatures in life detection missions. While there are also other sources of circular polarization, these result in spectrally flat signals with lower magnitude. Additionally, circular polarization can be a valuable tool in Earth remote sensing because the circular polarization signal directly relates to vegetation physiology. Aims. While high-quality circular polarization measurements can be obtained in the laboratory and under semi-static conditions in the field, there has been a significant gap to more realistic remote sensing conditions. Methods. In this study, we present sensitive circular spectropolarimetric measurements of various landscape elements taken from a fast-moving helicopter. Results. We demonstrate that during flight, within mere seconds of measurements, we can differentiate (S∕ N > 5) between grass fields, forests, and abiotic urban areas. Importantly, we show that with only nonzero circular polarization as a discriminant, photosynthetic organisms can even be measured in lakes. Conclusions. Circular spectropolarimetry can be a powerful technique to detect life beyond Earth, and we emphasize the potential of utilizing circular spectropolarimetry as a remote sensing tool to characterize and monitor in detail the vegetation physiology and terrain features of Earth itself.

Astrobiology
Earth
Planets and satellites: surfaces
Planets and satellites: terrestrial planets
Polarization
Techniques: polarimetric

http://resolver.tudelft.nl/uuid:f3e4533d-9311-4d2f-8640-b3cb805a38d4

https://doi.org/10.1051/0004-6361/202140845

0004-6361

Astronomy & Astrophysics, 651

Institutional Repository

journal article

© 2021 C. H.Lucas Patty, Jonas G. Kühn, Petar H. Lambrev, Stefano Spadaccia, C.U. Keller, W. Mulder, V. Pallichadath, Frans Snik, D.M. Stam, More Authors