Earthshine is light that’s reflected from the Earth to the moon, then back to the Earth again. Now scientists have discovered a way to use this shine to determine the amount of vegetation, water and cloud on our planet. Of course we already know this - but what’s significant is this technique could be used to analyse the surface of other far-off planets too.
The discovery was made by a group of astronomers from the European Southern Observatory using the Very Large Telescope. It involves a technique called spectropolarimetry - a combination of spectroscopy (studying matter and radiated energy through light) and light polarisation, resulting in being able to detect bio-signals in light - faint indicators of vegetation and water.
By analysing this further, the scientists were able to accurately find the makeup of clouds and water, breaking up their composition into oxygen, methane and other molecules.
“The light from a distant exoplanet is overwhelmed by the glare of the host star, so it’s very difficult to analyse - a bit like trying to study a grain of dust beside a powerful light bulb. But the light reflected by a planet is polarised, while the light from the host star is not. So polarimetric techniques help us to pick out the faint reflected light of an exoplanet from the dazzling starlight," said co-author of the earthshine study, Stefano Bagnulo, in a press release.
Because the scientists can find signals of water and plant life, they believe spectropolarimetry could be used to help find life on exoplanets.
“Finding life outside the Solar System depends on two things: whether this life exists in the first place, and having the technical capability to detect it. This work is an important step towards reaching that capability,” said study co-author Enric Palle.
[ESO]
