Astronomers Calculate How To Spot Life On an Alien Earth 46
KentuckyFC writes: "One of the main goals of the space program is to spot an Earth-like planet orbiting another star. And by Earth-like, astronomers mean a planet with liquid water, gaseous oxygen and even chlorophyll, or a light-harvesting molecule like it. The biosignatures of these molecules were all observed during the first Earth fly-by in 1990 when the Galileo spacecraft measured the light reflected off Earth as it flew past on its way to Jupiter. But if these biosignatures exist on more distant exoplanets, could we spot them today? Now astronomers have calculated how good the next generation of space telescopes will have to be to pick up these biosignatures of life. They say that gaseous water should be relatively straightforward to pick out and that oxygen will be more challenging. But the spectral signature of chlorophyll-like molecules will be much harder to spot, requiring significantly more sensitivity than is possible today (either that or a great deal of luck). That suggests a plan, they say. The next generation of space telescopes should look for water and oxygen on exoplanets orbiting nearby stars and only then begin the time-consuming and expensive task of looking for chlorophyll on the most promising targets. One spacecraft that might do this is the Advanced Technology Large-Aperture Space Telescope or ATLAST that is currently scheduled for launch in the 2025-2035 time frame."
Re:Chlorrophyll makes a big assumption (Score:4, Interesting)
ISTR that chlorophyll is essentially a "voltage doubler", basically for red light. (Leaves are green because they use the red, and discard/reflect the green.) If you consider red to be between 600nM and 700nM, then a little more UV than we get might deliver enough content between 300nM and 350nM to be used directly for photosynthesis. I wonder how much UV would be needed to bypass the doubler, and if that would be too much for life, in general. Of course that would mean a hotter sun than ours, and I've more recently heard more about searching around red dwarves, where the leaves would more likely look black.