The search for life in our solar system got a lot more exciting this week. On Monday, a team of scientists announced its members had detected phosphine gas in the caustic, hot atmosphere of Venus. So what? The gas \u2014 which you\u2019d recognize by its fishy odor \u2014 is thought to be a byproduct of life. <\/p>\n
\u201cWe did exhaustively search through all known chemistry … and we didn\u2019t find anything that could produce more than the tiniest amount of phosphine in Venus\u2019s atmosphere,\u201d says MIT planetary scientist Sara Seager, who was one of the co-authors on the discovery published in Nature Astronomy<\/em>, <\/em>says. That leaves us two possibilities: The gas was created by life or by some chemical interaction scientists don\u2019t yet know about. <\/p>\n Seager is one of the leading dreamers and thinkers in astronomy, looking for life beyond our planet. She studies planets orbiting stars many light-years away and thinks about how to detect life on them and others closer to home, like Venus.<\/p>\n She\u2019s also thinking creatively about the microscopic life forms that could potentially survive there. This summer, before the phosphine announcement, she and her co-authors published a speculative, hypothetical sketch of what life on Venus could look like. The vision is beautiful: a living rain of microbes floating, cyclically, in the clouds, blooming and desiccating continually for millions of years. <\/p>\n I wanted to hear more about this vision of life in a world so very different from our own, so I called her up. <\/p>\n This conversation has been edited for length and clarity.<\/p>\n Evidence for life on the planet next door To start off: What\u2019s the gist of the discovery that you and the team announced this week? <\/p>\n Sara Seager<\/p>\n We aren\u2019t claiming we found signs of life. We are claiming we have a robust detection of the gas phosphine in the atmosphere. <\/p>\n [After searching] all the known chemistry \u2014 volcanoes, photochemistry, lightning \u2014 we didn\u2019t find anything that could produce more than the tiniest amount of phosphine in Venus\u2019s atmosphere. So we\u2019re left with two possibilities. One is that there is some kind of unknown chemistry, which seems unlikely. And the other possibility is that there\u2019s some kind of life, which seems even more unlikely. So that\u2019s where we\u2019re at. It took a long time to accept it. <\/p>\n Brian Resnick<\/p>\n Okay, so it\u2019s very unlikely. Has Venus historically been thought of as a place life might exist in the solar system? <\/p>\n Sara Seager<\/p>\n It\u2019s been fringe pretty much the whole time that it\u2019s been a topic. Carl Sagan first proposed there could be life in [Venus\u2019s] clouds. There is a small group [of scientists] that writes about this topic. A lot of people love it. It\u2019s like a closeted love because a lot of people are enthusiastic about it, but they either didn\u2019t want to say so or they never had a reason to say so. <\/p>\n Brian Resnick<\/p>\n What do they love about it? <\/p>\n Sara Seager<\/p>\n I think it\u2019s just the intrigue that there could be life so close to home. <\/p>\n [Venus is closer to Earth than Mars. It\u2019s also the second-brightest object in our night sky, other than the moon.]<\/p>\n Why life would have to exist in Venus\u2019s clouds, not on the surface<\/p>\n Brian Resnick<\/p>\n As I understand it, if life exists on Venus, it wouldn\u2019t be on the surface of the planet, but in its sulfuric acid clouds? <\/p>\n Sara Seager<\/p>\n It\u2019s always been the theory because the surface is too hot for complex molecules. <\/p>\n Brian Resnick<\/p>\n What is too hot? What happens there?<\/p>\n Sara Seager<\/p>\n Molecules break apart. If you took a protein or an amino acid, or anything, and put it in high temperature, it would come apart into smaller fragments and atoms.<\/p>\n Brian Resnick<\/p>\n Why, then, is the atmosphere a better place to look for life?<\/p>\n Sara Seager<\/p>\n It has the things that astrobiologists think life needs. It needs a liquid of some kind. And there is liquid in the atmosphere, although it is liquid sulfuric acid. <\/p>\n Life needs an energy source. So there\u2019s definitely the sun, at least as an energy source. Life needs the right temperature. In the atmosphere, there is the right temperature. And life needs a changing environment to promote Darwinian evolution. So if you want to break it down like that, that\u2019s why. To simplify, it\u2019s mostly the temperature argument. Temperature and liquid. <\/p>\n
\nBrian Resnick<\/p>\n