A test for the search for life on extrasolar planets: Looking for the terrestrial vegetation signature in the Earthshine spectrum

TL;DR

This study analyzes Earthshine spectra to identify biosignatures like vegetation red edge, aiming to develop methods for detecting life on extrasolar planets through spectral signatures.

Contribution

It presents spectroscopic observations of Earthshine revealing vegetation signatures, advancing techniques for biosignature detection on exoplanets.

Findings

Detected variable signal around 700nm consistent with vegetation red edge

Spectra show Earth's blue color and atmospheric signatures of oxygen, ozone, water vapor

Potential for using spectral features to identify extraterrestrial vegetation

Abstract

We report spectroscopic observations (400 to 800nm, R = approx 100) of Earthshine in June, July and October 2001 from which normalised Earth albedo spectra have been derived. The resulting spectra clearly show the blue colour of the Earth due to Rayleigh diffusion in its atmosphere. They also show the signatures of oxygen, ozone and water vapour. We tried to extract from these spectra the signature of Earth vegetation. A variable signal (4 to 10 +/-3%) around 700nm has been measured in the Earth albedo. It is interpreted as being due to the vegetation red edge, expected to be between 2 to 10% of the Earth albedo at 700nm, depending on models. We discuss the primary goal of the present observations: their application to the detection of vegetation-like biosignatures on extrasolar planets.