How The JWST Could Detect Signs of Life on Exoplanets

Universe Today reports:The best hope for finding life on another world isn't listening for coded messages or traveling to distant stars, it's detecting the chemical signs of life in exoplanet atmospheres. This long hoped-for achievement is often thought to be beyond our current observatories, but a new study argues that the James Webb Space Telescope (JWST) could pull it off. Most of the exoplanets we've discovered so far have been found by the transit method. This is where a planet passes in front of its star from our point of view. Even though we can't observe the planet directly, we can see the star's brightness dip by a fraction of a percent. As we watch stars over time, we can find a regular pattern of brightness dips, indicating the presence of a planet. The star dips in brightness because the planet blocks some of the starlight. But if the planet also has an atmosphere, there is a small amount of light that will pass through the atmosphere before reaching us. Depending on the chemical composition of the atmosphere, certain wavelengths will be absorbed, forming absorption spectra within the spectra of the starlight. We have long been able to identify atoms and molecules by their absorption and emission spectra, so in principle, we can determine a planet's atmospheric composition with the transit method... We have done this with a few exoplanets, such as detecting the presence of water and organic compounds, but these were done for large gas planets with thick atmospheres. We haven't been able to do this with rocky Earth-like worlds. Our telescopes just aren't sensitive enough for that. But this new study shows that the JWST could detect certain chemical biosignatures depending on their abundance in the atmosphere. Long-time Slashdot reader Baron_Yam writes that "The signature I like to imagine detecting is actually industrial pollution. Chemicals that aren't created by any known geological process and indicate not just life, but life smart enough to have advanced technology (but stupid enough to pollute their own air supply)."Read more of this story at Slashdot.
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