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  • The search for life on other planets could get a boost from biosignatures | Los Angeles Times
    Thursday, January 25, 2018
    By studying the atmospheric contents of ancient and present-day Earth, scientists say they've discovered specific chemical combinations that could reveal the presence of biological activity on other planets. David Catling, a UW Earth and space sciences professor, is quoted. Joshua Krissansen-Totton, a doctoral student in Earth and space sciences at the UW, is mentioned. Read More
  • New technique could reveal hidden alien life | Yahoo! News
    Thursday, January 25, 2018
    A new approach to spotting alien biology at work could increase the chances of finding life on other planets. David Catling, professor of Earth and space sciences at the UW, and Joshua Krissansen-Totton, a doctoral student in Earth and space sciences at the UW, are quoted. (This UK wire story appeared in several outlets) Read More
  • Alien life hunt: Oxygen isn't the only possible sign of life | Space.com
    Thursday, January 25, 2018
    Alien-life hunters should keep an open mind when scanning the atmospheres of exoplanets, a new study stresses. Joshua Krissansen-Totton, a doctoral student in Earth and space sciences at the UW, is quoted. Read More
  • A new way to search for the tell-tale signs of life on distant exoplanets | Popular Mechanics
    Thursday, January 25, 2018
    By looking for specific chemical combinations in the atmospheres of planets orbiting other stars, astronomers might be able to detect conditions suitable for life. Joshua Krissansen-Totton, a UW doctoral student in Earth and space sciences, is quoted. Read More
  • A new recipe for hunting alien life | Scientific American
    Thursday, January 25, 2018
    Imagine stepping into a time machine, one that could traverse not only billions of years but also countless light years of space, all in search of life in the universe. Where would you find most of it, and what would it look like? The answer--or at least scientists' best guess--might surprise you. David Catling, professor of Earth and space sciences at the UW, is quoted. Earth and space sciences graduate student Joshua Krissansen-Totton is mentioned. Read More
  • This new method to search for life doesn't rely on oxygen | IFLScience
    Thursday, January 25, 2018
    Scientists have proposed a new way to search for life, by looking for an imbalance of certain gases in the atmospheres of other planets. Joshua Krissansen-Totton, a UW doctoral student in Earth and space sciences, is quoted. Read More
  • Alien life: Weird 'biosignatures' help scientists hunt for extraterrestrials | Newsweek
    Thursday, January 25, 2018
    Scientists have found a new way to hunt for alien life on distant exoplanets. Clashing gas signatures could mark a planet as habitable from millions of miles away. Joshua Krissansen-Totton, a UW doctoral student in Earth and space sciences, and David Catling, a professor of Earth and space sciences at the UW, are quoted. Read More
  • How to find life on distant planets: maybe try looking for carbon dioxide and methane | The Verge
    Thursday, January 25, 2018
    One way to find life outside our Solar System is to peer into the atmospheres of distant planets, looking for gases that may be produced by living organisms. A team of scientists at the UW thinks we should look for two gases in particular: carbon dioxide and methane. Joshua Krissansen-Totton, a UW doctoral student in Earth and space sciences, is quoted. Read More
  • NASA could detect alien life using telescope-powered 'sniff test' | Business Insider
    Thursday, January 25, 2018
    A new study from scientists at the University of Washington argues that telescopes could perform a new kind of "sniff test" for life, looking for gases like methane and carbon dioxide that might bring new clues about where other organisms could exist. Read More
  • A new 'atmospheric disequilibrium' could help detect life on other planets
    Wednesday, January 24, 2018

    As NASA’s James Webb Space Telescope and other new giant telescopes come online they will need novel strategies to look for evidence of life on other planets. A University of Washington study has found a simple approach to look for life that might be more promising than just looking for oxygen.

    illustration of telescope and planets

    Future telescopes like the James Webb Space Telescope (right) will observe the atmospheres of distant planets to seek evidence of life. Earth (top left) has several gases in its atmosphere that reveal the presence of life, primarily oxygen and ozone. The new study finds that for the early Earth (bottom left), the combination of abundant methane and carbon dioxide would provide an alternative sign of life.NASA/Wikimedia Commons/Joshua Krissansen-Totton

    The paper, published Jan. 24 in Science Advances, offers a new recipe for providing evidence that a distant planet harbors life.

    “This idea of looking for atmospheric oxygen as a biosignature has been around for a long time. And it’s a good strategy -- it’s very hard to make much oxygen without life,” said corresponding author Joshua Krissansen-Totton, a UW doctoral student in Earth and space sciences. “But we don’t want to put all our eggs in one basket. Even if life is common in the cosmos, we have no idea if it will be life that makes oxygen. The biochemistry of oxygen production is very complex and could be quite rare.”

    The new study looks at the history of life on Earth, the one inhabited planet we know, to find times where the planet’s atmosphere contained a mixture of gases that are out of equilibrium and could exist only in the presence of living organisms -- anything from pond scum to giant redwoods. In fact, life's ability to make large amounts of oxygen has only occurred in the past one-eighth of Earth’s history.

    By taking a longer view, the researchers identified a new combination of gases that would provide evidence of life: methane plus carbon dioxide, minus carbon monoxide.

    “We need to look for fairly abundant methane and carbon dioxide on a world that has liquid water at its surface, and find an absence of carbon monoxide,” said co-author David Catling, a UW professor of Earth and space sciences. “Our study shows that this combination would be a compelling sign of life. What’s exciting is that our suggestion is doable, and may lead to the historic discovery of an extraterrestrial biosphere in the not-too-distant future.”

    The paper looks at all the ways that a planet could produce methane -- from asteroid impacts, outgassing from the planet’s interior, reactions of rocks and water -- and finds that it would be hard to produce a lot of methane on a rocky, Earth-like planet without any living organisms.

    If methane and carbon dioxide are detected together, especially without carbon monoxide, that’s a chemical imbalance that signals life. The carbon atoms in the two molecules represent opposite levels of oxidation. Carbon dioxide holds as many oxygen molecules as it can, while the carbon in methane lacks oxygen and instead has oxygen’s chemical adversary, hydrogen.

    “So you’ve got these extreme levels of oxidation. And it’s hard to do that through non-biological processes without also producing carbon monoxide, which is intermediate,” Krissansen-Totton said. “For example, planets with volcanoes that belch out carbon dioxide and methane will also tend to belch out carbon monoxide.”

    What’s more, carbon monoxide tends not to build up in the atmosphere of a planet that harbors life.

    “Carbon monoxide is a gas that would be readily eaten by microbes,” Krissansen-Totton said. “So if carbon monoxide were abundant, that would be a clue that perhaps you’re looking at a planet that doesn’t have biology.”

    The authors agree that oxygen is a good way to look for signs of life, but think that this new combination is at least as likely to pop up through the new telescopes’ sights.

    “Life that makes methane uses a simple metabolism, is ubiquitous, and has been around through much of Earth’s history,” Krissansen-Totton said. “It’s an easy thing to do so it’s potentially more common than oxygen-producing life. This is definitely something we should be looking for as new telescopes come online.”

    The other co-author is Stephanie Olson at the University of California, Riverside. The research was funded by NASA.

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    For more information, contact Krissansen-Totton at joshkt@uw.edu or 206-402-7007 and Catling at dcatling@uw.edu.

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