Biosignatures as revealed by spectropolarimetry of Earthshine

Earthshine is reflected Earth's light visible on the Moon's night side.


Study of the Earthshine provides information about what has reflected light coming from the Sun.  Indeed, properties are different whether light is reflected off oceans or continents. Light can also be scattered by air molecules, aerosols or cloud particles when passing through the Earth's atmosphere.

Light which has been reflected/scattered becomes strongly linearly polarized. Therefore, using spectropolarimetric observations (measurements of the polarization at several wavelengths or colors), it is possible to detect the spectral signatures of aerosols, clouds, etc...but also from vegetation. European astronomers have used this technique to determine the fractional contribution of clouds and ocean surface. The results are sensitive to visible areas of vegetation as small as 10 per cent.

These results represent a benchmark for the diagnostics of the atmospheric composition, mean cloud height and surfaces of exoplanets, planets orbiting around other stars.

These results have been published in Nature.  One of the authors, Dr. Stefano Bagnulo from Armagh Observatory (UK) is an active member of this COST Action.

Related links :

- Original paper published in Nature

- ESO Press release : VLT rediscovers Life on Earth

- Press release from Armagh Observatory: Astronomers search for life

- Article in the French newspaper Libération : Il y a de la vie sur Terre, la Lune le dit

- Article in the French newspaper Le Monde : Quand La Lune reflète la vie terrestre