Astronomers detect signs of life on Earth
Light detector Scientists have developed a new method to study reflected light from the Earth, that can correctly measure the amount of cloud cover, ocean and vegetation our planet has.
The research, reported in the journal Nature, will allow astronomers to eventually study the atmospheric and surface features of planets in other solar systems.
Scientists including Dr Michael Sterzik from the European Southern Observatory in Chile, used spectroscopy and light polarisation to look for chemical bio-signatures in Earthshine - sunlight reflected by the Earth onto the surface of the Moon and back again.
Light passing through the Earth's atmosphere contains a tell-tale spectrum revealing the elements within the gas. It is also strongly polarised by scattering from air molecules, aerosols and cloud particles, and by reflection off the oceans and land.
By combining these characteristics in a technique called spectropolarimetry, Sterzik and colleagues successfully obtained information about the Earth from reflected light that wouldn't be achieved by normal spectroscopic readings alone.
They report finding molecular oxygen, methane, as well as ozone and water vapour, which were used to characterize the properties of clouds and aerosols.
The readings allowed them to determine the contribution of cloud, ocean surface and vegetation to the signatures.
The measurements are sensitive enough to detect visible areas of vegetation as low as 10 per cent.
"The paper is a proof of concept, demonstrating that you can use spectropolarimetry to measure bio-signatures in the reflected light of planets orbiting other stars," says University of Melbourne astrophysicist Professor Stuart Wyithe who was not part of the study.
"Unlike stars, planets don't produce their own light, they only reflect the light produced by their host star."
Wyithe says this latest research is the first time the technique has produced such an accurate result.
"All that's needed now is a sensitive enough instrument to see these extra solar planets."