"Exo Planets Could Act as Giant Mirrors to Reveal Signs of Organic Life" --The ESO

          


By studying Earth's Moon using The ESO's Very Large Telescope in Chile (below), an international team of astronomers have used a novel approach that may lead to future discoveries of life elsewhere in the Universe.  Using a technique called earthshine observation to look at the Earth as if it were an exoplanet. This method establishes the Earth as a benchmark for the future search for life on planets beyond our Solar System.

"The Sun shines on the Earth and this light is reflected back to the surface of the Moon. The lunar surface acts as a giant mirror and reflects the Earth's light back to us — and this is what we have observed with the VLT," says Michael Sterzik (ESO), lead author of the paper. The astronomers analyzed the faint earthshine light to look for indicators, such as certain combinations of gases in the Earth's atmosphere, that are the telltale signs of organic life. 

When the Moon appears as a thin crescent in the twilight skies of Earth it is often possible to see that the rest of the disc is also faintly glowing. This phenomenon is called earthshine. It is due to sunlight reflecting off the Earth and illuminating the lunar surface. 

After reflection from Earth the colors in the light are significantly changed. By observing earthshine astronomers can study the properties of light reflected from Earth as if it were an exoplanet and search for signs of life. The reflected light is also strongly polarised and studying the polarisation as well as the intensity at different colours allows for much more sensitive tests for the presence of life. 

The fingerprints of life, or biosignatures, are hard to find with conventional methods, but the team has pioneered a new approach that is more sensitive. Rather than just looking at how bright the reflected light is in different colours, they also look at the polarisation of the light, an approach called spectropolarimetry. By applying this technique to earthshine observed with the VLT, the biosignatures in the reflected light from Earth show up very strongly.

"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," explains Co-author Stefano Bagnulo of Armagh Observatory, Northern Ireland. "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."

The team studied both the color and the degree of polarisation of light from the Earth after reflection from the Moon, as if the light was coming from an exoplanet. They managed to deduce that the Earth's atmosphere is partly cloudy, that part of its surface is covered by oceans and — crucially — that there is vegetation present. They could even detect changes in the cloud cover and amount of vegetation at different times as different parts of the Earth reflected light towards the Moon.

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," adds co-author Enric Palle (Instituto de Astrofisica de Canarias, Tenerife, Spain). "This work is an important step towards reaching that capability."

"Spectropolarimetry may ultimately tell us if simple plant life — based on photosynthetic processes — has emerged elsewhere in the Universe," concludes Sterzik. "But we are certainly not looking for little green men or evidence of intelligent life."

The next generation of telescopes, such as the E-ELT (the European Extremely Large Telescope), may well be able to bring us the extraordinary news that the Earth is not alone as a bearer of life in the vastness of space.

 

          

The Daily Galaxy via The ESO

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Comments

[John Doe]

I'm confident that the next generation of telescopes will deliver the ultimate proof that our precious earth is just one of many worlds teeming with life (simple or intelligent)!

Interesting times...

[ibuzone]

I want to know how long it will take to find out if another planet has life.

[Paul]

While it is very cool that we can detect the signals emitted by organic life as reflected off of a moon, it seems like a rather convoluted way of sensing life. Just look at the planet directly - the signals are much stronger.

[Andrew]

This team probably looked at reflected Earthshine from the Moon as a proxy for looking at the Earth as an astronomical object. For extrasolar planets it probably would be best to go after the planets themselves. If you think about it, a planet is a bigger reflector than its moons, so most of the light you got would be from the planet.

Going after polarized light is a very good idea. Reflected light tends to be polarized while the starlight tends to be unpolarized. This might be a good way to detect or confirm extrasolar planets in general. Analyzing the spectrum for life is a happy bonus.

I'd like to suggest a few targets. First, GJ 667C c since it's fairly close, has already been confirmed, and according to the Planetary Habitability Lab is the most Earth-like of all the confirmed extrasolar planets. If this method can detect GJ 667C c, I'd then suggest unconfirmed Kepler targets. Of these I'd start with KOI-494.01 and KOI-736.01 since they're the most Earth-like planetary candidates known at this time.

[Matt]

"This team probably looked at reflected Earthshine from the Moon as a proxy for looking at the Earth as an astronomical object. For extrasolar planets it probably would be best to go after the planets themselves. If you think about it, a planet is a bigger reflector than its moons, so most of the light you got would be from the planet."

Ditto. This has nothing to do with "Alien moons". This is probably the most erroneous titles I've seen from The Daily Galaxy (I have noticed quite a few).

Editor's Note: Hey Matt, you're right. We corrected the headline. Thanks.

[Neocast]

The discovery of planet KO1-494.01 is a fascinating discovery, not to mention mind blowing where speculation and imagination run wild. Unfortunately at a jaw dropping 1,242 light years away and assuming that Albert Einstein's formulas and theory checks out, it would be a millenia or two to get a technology worthy of ever studying this wonderland. Let Us not forget that the most distant space probe, Voyager 1, was about 16 light-hours away from the Earth as of 2011. It will take about 17,500 years to reach one light-year at its current speed of about 17 km/s (38,000 mph) relative to the Sun. So even if we were to achieve the means to multiply this kind of speed times 5- times we have a long way to go.