Wednesday, May 07, 2014

Could We Soon Detect Alien 'Plant' Life on Exoplanets?

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Could We Soon Detect Alien 'Plant' Life on Exoplanets?

By Ian O'Neill

      Now we’re detecting dozens of exoplanets within the habitable zones of their stars — and even one world that has similar characteristics as Earth — the next big question will be: do any of these promising worlds host life?

Unfortunately, the answer will remain elusive for some time to come, but that hasn’t stopped scientists from formulating plans to seek out alien biomarkers that could be ripe for detection.

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In a new paper submitted to the arXiv preprint service, astrophysicists Timothy Brandt and David Spiegel of the Institute for Advanced Study at Princeton University, New Jersey, focused on the hunt for the chemical signature of oxygen, water and chlorophyll in the atmospheres of Earth-like exoplanetary atmospheres. Oxygen and water are essential for life as we know it, and chlorophyll is a biomolecule vital for photosynthesis on Earth. Photosynthesis is the extraction of energy from sunlight, a process employed by plants and some microbes, such as cyanobacteria.

So the logic goes: If we can detect these molecules on an Earth-sized alien world, there could be some not-so-unfamiliar form of extraterrestrial life that has evolved to produce chlorophyll to extract energy from their star.

But the challenges to detect such signals are overwhelming, at least for the technology we have today. So the researchers have constructed some computer models in an effort to create hypothetical “second Earths” and the chemical signatures we may detect from afar.

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The key issue facing any future space telescope set up to search for “Earth 2.0″ is that of contrast. Although analyzing the spectroscopic signature of large exoplanets has been done, often these worlds have wide orbits (well outside the habitable zone) or they are very large (like “hot-Jupiters”). Extracting a spectroscopic signal from a small world within the habitable zone of their star is tough, as the light from the star will overwhelm any reflected starlight signal from the exoplanet. The signal-to-noise ratio will be, basically, horrible.

This is where sophisticated models come in handy; if you can model an exoplanetary atmosphere with components similar to that of Earth, we know what chemical fingerprints to look for in observational data.

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