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The James Webb Space Telescope (JWST) which is slated to launch in 2018 will bring us a better view of exoplanets, but will it be sufficient to detect signs of life on at least some of those worlds?

A good answer will provide an estimate of the James Webb Space Telescope's capabilities to detect atmospheric data relevant to the presence of life.

The preferred answer would also include an analysis of what it would take to say with a decent level of confidence that life was present on an exoplanet and whether or not JWST will be capable of this.

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    $\begingroup$ I think that the fundamental (no, the practical) question really is what life has to make up in order to make it self detectable to our instruments. We could try to reason about the probability for that. Ozone in a relatively nearby exoplanetary atmosphere seems to be the best for JWST to hope finding. But looking at ourselves which unfortunately is the only sample of life, and considering the complexity of microbiology, well we couldn't make this stuff up (Microbes just say: Don't call us, we'll make you). $\endgroup$ – LocalFluff Jul 6 '15 at 14:57
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From what I understand, James Webb, if used in conjunction with a successful starshade (being developed at MIT), should be able to detect close in planets orbiting nearby stars. However, getting good atmospheric spectra of these planets directly (from planet's blackbody IR emission) is unlikely. What we must hope for is that TESS, which should be going up in 2017, will find a few nearby stars with transiting planets. Then, James Webb will be able to look for atmospheric absorption lines from stellar light passing through a planet's atmosphere during transit. This method may still be limited to large (Jupiter size) planets. In an ideal situation (say looking at absorption lines of a super-earth) there are many "bio-signatures", but one of the easiest to detect would be an ozone line in the infrared. By itself, this would not be proof, even though there would need to be a constant replenishing source of O2 in the atmosphere to maintain the O3. If methane could also be found we could rightly get VERY excited since methane and oxygen don't co-exist very well.

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    $\begingroup$ Great summary, thanks for returning to this old post. $\endgroup$ – called2voyage Sep 13 '15 at 21:37
  • $\begingroup$ TESS delayed til 2018 $\endgroup$ – Jack R. Woods Nov 30 '15 at 23:05

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