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Air Pollution that is Out Of This World


An artist's rendering of a polluted exoplanet. (Image credit: Christine Pulliam (CfA))


It probably comes as no surprise to you, given the profession that I’m in, that I’m very much into science. I was destined to be in science as I was born at Cape Kennedy, FL while my father worked on the Apollo project. I was even at the launch of Apollo 11, although I’m told that I was more interested in playing with the sand on the beach than watching the Saturn V launch as I was but a few months old!


Like many people these days I’m eagerly awaiting the launch of the James Webb Space Telescope (JWST), currently slated for Christmas morning on the east coast of the United States. Lifting off from the French and European spaceport in French Guiana, over the next few months JWST will set up shop about one million miles from Earth, at the L2 Lagrange point on the opposite side of the moon from us. The information that the scientific community hopes to gain from JWST’s observations is nothing short of a game-changer for humanity. That may sound like hyperbole, but if anything, I’ve understated it.


JWST is much bigger than the current star (pun intended) of astronomy, the Hubble Space Telescope. However, the biggest difference between JWST and the Hubble might be in how they each “see” the universe—Hubble observes light at primarily optical and ultraviolet wavelengths, while JWST will primarily detect infrared light.


The advantage of detecting infrared is that when you’re looking very far away in the universe, you’re seeing light that has been traveling for billions of years—and over that tremendous time and distance that light has been stretched. As that wavelength gets longer the light that used to be in the visible spectrum ends up shifting down into the infrared spectrum. So, by looking in the infrared the JWST will be able to detect light that’s no longer visible, but is still there. That means that the JWST will be able to peer back to the literal dawn of the universe (at objects approaching 13.8 billion years old), and will be capable of detecting any galaxy in the universe. Think of that. Any galaxy in the universe.


If that isn’t exciting enough, the JWST is going to give us a completely new understanding of exoplanets—planets that we have detected orbiting other stars. When I was growing up, we knew of only nine planets (at the time Pluto was a planet), but as of December 1 of this year the count is 4,878 planets in 3,604 systems (not counting our own solar system). The JWST is going to be able to focus on an exoplanet and give us a chemical breakdown of its atmosphere. So if methane is detected, for instance, that may be a sign of life because methane is often produced by microorganisms.


But there’s another way that the JWST might be able to find signs of life—to look for air pollution. The JWST will be able to detect chemicals that are predominantly the result of an industrialized civilization—for example, nitrogen dioxide (NO2) from combustion. The idea is that if the JWST detects NO2 in an exoplanet’s atmosphere at levels above non-technological emissions found on Earth, that could be a sign of an advanced civilization.


Obviously if a civilization is advanced enough to have found “cold fusion” they may not have high levels of air pollution in their atmosphere, so this is but one piece of the puzzle of looking for life elsewhere. But I must admit, a big part of me is hoping we find an exoplanet that hasn’t figured out how to control its NO2 emissions yet, because finding strong evidence of life elsewhere would pretty much rank as the biggest bit of science news in my lifetime.

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