Session 3: Are We Alone?

Moderator:

Robert T. Pappalardo, Jet Propulsion Laboratory, California Institute of Technology; Space Studies Board Member

Speakers:

Sara Seager, Massachusetts Institute of Technology

Steven Benner, Foundation for Applied Molecular Evolution

Panelists:

Marc Kaufman, Journalist, The Washington Post

Stephen Mautner, The National Academies Press

INTRODUCTION

Robert T. Pappalardo, senior research scientist at the Jet Propulsion Laboratory at the California Institute of Technology and Space Studies Board (SSB) member, opened the session by commenting that the question, Are We Alone? continues to fascinate the scientific community and the public. Candidates for life in our solar system include Mars, Europa, and Titan. Other possibilities lie on planets in other solar systems around other stars—exoplanets.

Astrobiology, the search for life and life’s origins, could change our sense of place in the universe, but most of it is a search for microbes, not intelligent life. Pappalardo wondered aloud if the public understands that. If extraterrestrial microorganisms are discovered, the scientific community would proclaim a new scientific revolution, but would the public care, he asked?

SARA SEAGER

Sara Seager, Ellen Swallow Richards Professor of Planetary Science and Professor of Physics at the Massachusetts Institute of Technology, began by talking about the challenge of finding Earth-like planets elsewhere in the universe. Showing an image of Earth taken by NASA’s Voyager 1 spacecraft looking back toward Earth when it was 4 billion miles away (Figure 4), Seager demonstrated the difficulty of trying to find a planet embedded in a ring of dust—”it won’t be spatially resolved,” she said. It also is difficult to find a planet around a star in visible wavelengths because the planet would be close to a star that is “10 billion times brighter.”

Scientists have identified a “Goldilocks zone” or “habitable zone” around stars where the temperature on a planet in that zone would be not too hot and not too cold, but just right for liquid water, which scientists believe is a prerequisite for life. Seager acknowledged that it is a “terracentric” view, and that would be addressed in Session 4.

image

FIGURE 4 Earth as a pale blue dot. SOURCE: Courtesy of NASA Jet Propulsion Laboratory.



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Session 3: Are We Alone? Moderator: Robert T. Pappalardo, Jet Propulsion Laboratory, California Institute of Technology; Space Studies Board Member Speakers: Sara Seager, Massachusetts Institute of Technology Steven Benner, Foundation for Applied Molecular Evolution Panelists: Marc Kaufman, Journalist, The Washington Post Stephen Mautner, The National Academies Press INTRODUCTION Robert T. Pappalardo, senior research scientist at the Jet Propulsion Laboratory at the California Institute of Technology and Space Studies Board (SSB) member, opened the session by commenting that the question, Are We Alone? continues to fascinate the scientific community and the public. Candidates for life in our solar system include Mars, Europa, and Titan. Other possibilities lie on planets in other solar systems around other stars—exoplanets. Astrobiology, the search for life and life’s origins, could change our sense of place in the universe, but most of it is a search for microbes, not intelligent life. Pappalardo wondered aloud if the public understands that. If extraterrestrial microorganisms are discovered, the scientific community would proclaim a new scientific revolution, but would the public care, he asked? SARA SEAGER Sara Seager, Ellen Swallow Richards Professor of Planetary Science and Professor of Physics at the Massachusetts Institute of Technology, began by talking about the challenge of finding Earth- like planets elsewhere in the universe. Showing an image of Earth taken by NASA’s Voyager 1 spacecraft looking back toward Earth when it was 4 billion miles away (Figure 4), Seager demonstrated the difficulty of trying to find a planet embedded in a ring of dust— ”it won’t be spatially resolved,” she said. It also is difficult to find a planet around a star in visible wavelengths because the planet would be close to a star that is “10 billion times brighter.” Scientists have identified a “Goldilocks zone” or “habitable zone” around stars where the temperature on a planet in that zone would be not too hot and not too cold, but just right for liquid water, which scientists believe is a prerequisite for life. Seager acknowledged that it is a “terracentric” view, and that would be addressed in Session 4. FIGURE 4 Earth as a pale blue dot. SOURCE: Courtesy of NASA Jet Propulsion Laboratory. 22

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Seager went on to summarize a recent announcement about scientists finding a planet in the Goldilocks zone around the red dwarf star Gliese 581.1 She reminded the audience that it was a “three sigma result” or has a “confidence level of 99.7 percent,” meaning that there are three chances in a thousand that it is wrong. This level of uncertainty is acceptable in science, “but it could be wrong,” she stressed. She then discussed what she considered the less-than-optimal method by which the finding was announced. The National Science Foundation (NSF) held a “hush, hush” press conference that could only be attended by a select group, she said, and NSF embargoed all the data until after the press conference. Consequently, a competing scientific team from Switzerland announced 2 weeks later at a meeting in Italy that it had different data from the U.S. scientists, and they saw no evidence of a planet. The U.S. team’s data were published in a scientific journal, but the Swiss team did not release their data, so it is difficult for scientists like herself to determine what is going on without documentation. Further analysis must wait for the Swiss team’s data. She added on a positive note that the episode did stimulate interest in exoplanets in the media. Seager talked about the large number of exoplanets that have been found to date using a variety of methods. “Any kind of planet you can imagine exists somewhere,” she said. The search for Earth-size planets is the task of NASA’s new Kepler space telescope. It will tell us “how common are other Earths.” It will find Earth-size planets, but she emphasized again they are not necessarily Earth-like planets. Although Kepler is finding Earth-size planets, direct imaging 2 is necessary to find Earth-like planets (“Earth twins”). Scientists will not be able to directly image a planet the size of Earth with good spatial resolution for the next 100 years, she said, comparing it to trying to see a firefly next to a search light at the distance of the west coast to the east coast of the United States. What is needed, she said, is the Terrestrial Planet Finder mission that has been proposed but not yet approved by NASA. “People are really working on this,” Seager said, and “if we had the money, we could do it.” Absent that mission, scientists are looking for gases in the atmospheres of exoplanets that could indicate if life exists or could exist there. We won’t find life, she said, but may find signs of life, even though “we’ll never be 100 percent sure.” Seager joked that Jill Tarter, a prominent scientist at the Search for Extraterrestrial Intelligence (SETI) Institute, laughs when Seager says that because SETI scientists will be 100 percent sure when their search succeeds. SETI uses radio telescopes to search for signals from other intelligent civilizations. Seager ended her talk by saying that people who work in exoplanet research have an idealistic vision that they can change the way we see ourselves in the universe—”we really think we can change the world.” STEVEN BENNER Steven Benner, distinguished fellow at the Foundation for Applied Molecular Evolution, broadened the discussion to talk about life forms that might be quite different from the liquid-water- based, carbon-based life we know. It is especially difficult to search for life that could be completely different from anything the searchers know, he stressed. Delving into some detail about the chemistry of life, Benner explained that despite the millions of examples of life on Earth (“terran” life), the closer one looks the more they are the same at the molecular level. Four nucleobases, or “letters,” in the deoxyribonucleic acid (DNA) “alphabet” “are all shared by all terran life,” he said. 1 Seager explained that at least six planets have been observed about Gliese 581. The one in the “Goldilocks zone” is Gliese 581G. Gliese 581 is 20.3 light years from Earth in the constellation Libra. 2 Kepler stares at stars watching for objects that move across (“transit”) their faces at regular intervals, which suggests they are planets. It does not actually see the planet with any fine degree of resolution like taking a picture, as direct imaging would do. 23

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Synthetic biology has created a different genetic system in the laboratory that is capable of Darwinian evolution with 12 letters instead of four. “You don’t know how to look for six-letter DNA,” however, when everything you know is four-letter DNA. Nonetheless, there is a good chance that there is life completely unlike terran life elsewhere, he said. Mars looks more hospitable to life than it did in the 1960s because more probes have been sent there and evidence continues to emerge about the possible presence of life in the past. Today, Benner said, we talk about the probabilities of life there. That led Benner into a discussion about the “paradox of origins”—the difference between chemistry and Darwinian chemistry. Life takes liquid water, organic matter, and energy, but those three ingredients do not guarantee life. He explained that Stanley Miller showed that if you add energy to organic matter and water the result is tar—that’s what you get in the absence of Darwinian processes (Figure 5). If you take Cheerios and put them in the microwave you don’t expect a life form to emerge, he joked (Figure 6). The central problem in determining the origins of life then is making the leap from chemistry to Darwinian chemistry. If you put energy into organics, you don’t get closer to life, you get further from life, and that is the paradox, he said. Minerals may have helped life originate. Some boron-containing minerals constrain the tar forming capabilities of natural organics and give us ribose, the “R” in RNA (ribonucleic acid), which may be the first genetic molecule on Earth. “But this is just a model and is paradoxical in the extreme”—plagued by the paradoxes of the tar problem, the complexity problem, and the water problem. Water, the basis for life as we know it, “is bad for living things,” he went on, because “every bond marked in red falls apart in water” (Figure 7). Human beings tolerate the corrosivity of water by spending energy on repairing the bonds. Benner then asked whether water is necessary for life. Using Titan as an example, with its oceans of liquid methane and the Kauffman hypothesis3 that “the more complex the environment, the greater the likelihood life emerged within it.” He summarized four possibilities about whether life might exist on Titan: • If complexity is sufficient for life, then Titan has life; • If the corrosiveness of water is limiting, then Titan is more likely to have life; • But if tar contains inhibitors of life, then complexity is inimical to life; • But if minerals help manage organic complexity, then perhaps life is common on the right kind of planet. He ended by saying that the current generation of problems in searching for life is easily stated in the language of chemistry, “but journalists don’t convey chemistry well.” He listed the problems as: the tar problem, the water problem, the complexity problem, the universal genetic molecule, and the universal metabolism. It is possible that “weird life” is just under our feet, he said, noting that the microscope let us discover a whole biosphere we did not know about. There are four ways to search for life: prebiotic chemistry, synthetic biology, paleogenetics, or searching the cosmos. There are exciting possibilities in each of those approaches, he said.4 3 Stuart A. Kauffman, At Home in the Universe. The Search for the Laws of Self-Organization and Complexity, Oxford University Press, New York, N.Y., 1995. 4 Steven Benner cited two publications that explain his topic in more detail for further reference: The Limits of Organic Life in Planetary Systems (National Research Council, The National Academies Press, Washington, D.C., 2007) and Life, the Universe, and the Scientific Method, by Benner himself (The FfAME Press, 2009), which, he said with a smile, is intended to explain the first report. He was a member of the NRC committee that wrote the 2007 report. 24

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FIGURE 5 The paradox of origins. SOURCE: Steven Benner, Foundation for Applied Molecular Evolution, presentation to the workshop on Sharing the Adventure with the Public⎯The Value and Excitement of “Grand Questions” of Space Science and Exploration, November 9, 2010. Photo of Stanley Miller courtesy of NASA. FIGURE 6 Adding energy to organic matter. SOURCE: Steven Benner, Foundation for Applied Molecular Evolution, presentation to the workshop on Sharing the Adventure with the Public⎯The Value and Excitement of “Grand Questions” of Space Science and Exploration, November 9, 2010. Image courtesy of Steven A. Benner, Life, the Universe, and the Scientific Method, The FfAME Press, Gainesville, Fla., 2009, with permission. 25

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FIGURE 7 Water is bad for living things. SOURCE: Steven Benner, Foundation for Applied Molecular Evolution, presentation to the workshop on Sharing the Adventure with the Public⎯The Value and Excitement of “Grand Questions” of Space Science and Exploration, November 9, 2010. PANEL DISCUSSION Marc Kaufman, a journalist with the Washington Post and author of a recent book on astrobiology, and Steve Mautner, executive editor of the National Academies Press, joined Pappalardo, Seager, and Benner on the panel. Pappalardo began by asking Kaufman about the extent to which the press has to get a story right, Does it matter to the public? Kaufman replied that it is inevitable that there are factual inaccuracies in every newspaper story about science, and “yes, it matters.” He said the message to the public about the martian meteorite ALH 84001 was confusing because initial reports were that it did contain biosignatures, and later scientists were not certain that it did. However, with regard to the Gliese 581 story, shortly after the announcement, a second set of scientists said that there were hundreds of Earth-like planets in the universe. In his opinion, it therefore is less important whether the Gliese 581 finding is accurate because the general point the public needs to understand is that there are other habitable planets outside the solar system. Seager stressed that the second set of scientists did something quite different from the Gliese 581 researchers, however. They had statistics, that was all, and they made assumptions and extrapolations to get to their conclusion that 25 percent of stars like the Sun will have an Earth-mass planet within a 50-day period orbit. It was only a statistical statement, which may not have been conveyed to the public. Kaufman reiterated that the point that did come across, that he believes is correct, is that the chances are high that there are billions of stars that have Earth-size planets. Benner emphasized that it is not the job of scientists or the media to represent science as anything other than what it is—there will, at times, be wrong answers and the need for a possible reinterpretation of data. Scientists “are not better than the average bear” and should not be represented that way. The conversation broadened to discuss methods of conveying science information and whether Twitter’s 140-character limit is enough. Pappalardo asked about the fate of the National Academies 26

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Joseph Henry Press, which aimed to popularize science but no longer exists. Mautner said that the Joseph Henry Press did well by almost anyone’s standards, but the enterprise of book publishing changed with the way information is now delivered. He said a key question is what size dose of information is being conveyed and to what audience. He believes there is room for all types of communication. Seager agreed and reminded the audience that tweets and Facebook both can link to other information sources. Kaufman remarked that, as someone who had just written a book, he does believe there is still a future for books because some portion of the public will want that level of detail. The degree of interest in topics like the Grand Questions is an untapped market, he believes, citing the 8,000 Facebook shares of an article he wrote on habitable zones as an example. Seager read from a Facebook message she received from a colleague in Canada who wanted to point out to the workshop audience that there have been many forms of new communications in the past century and the “social media” are just the latest, and their full implications are not yet known. Pappalardo steered the conversation toward the issue of how to keep the public interested as scientists travel down the path to new discovery. “If we find microbes” and not people on Mars “will the people care?” Benner said the situation already occurred with ALH 84001, and they were fascinated. Mautner asked, “How do you sustain interest in the painstaking process [of] getting to a major scientific discovery?” Seager said that as far as exoplanets are concerned, there is enough interest: “We’re turning science fiction into science fact.” Benner offered that he detects no intolerance on the part of the public for the “struggle” and “incrementalism” inherent in science. Kaufman agreed, but cautioned that there is “danger when incremental change is miniscule” because with a dwindling cadre of science writers, the media may decide that something is no longer a story worth covering. AUDIENCE INTERACTION NASA’s Alan Ladwig asked about the role that e-books will play and mentioned that NASA’s history office is starting to switch over to e-books. Kaufman commented that there is “mud wrestling” going with the different e-book readers, and that Seager’s decision to start with an e-book, instead of a hardcover book that is later turned into an e-book, is “revolutionary.” Mautner said that the environment for e-books has changed dramatically in the past 3 to 4 years, but wondered generally whether there will be a market for book-length products in the future since “we are evolving into people with shorter attention spans.” The conversation then turned to the interrelationship between science and religion. A woman in the audience pointed to what she views as growing constraints on teaching evolution. She asked about how to reach “the gatekeepers”—junior and senior high school teachers—with regard to the Grand Questions of science and why this workshop did not have an evening session so they could attend. Pappalardo responded that the SSB is still trying to learn about the issues associated with communicating with the public and was not yet ready to reach out to them, which is what this workshop is about. Kennel picked up on the woman’s comment about creationists—those who do not believe in evolution—and asked why it is that when a discovery is made in astrobiology, the media does not seem to go to the creationists to get their viewpoint, but in climate science, the media regularly go to the “climate denialists.” Why are the two topics treated so differently by the media? he asked. Benner said that climate scientists have difficulty because the topic is closely tied to public policy and “so easily corrupted by people trying to subvert science for their own policy goals.” Kaufman said that in writing his book on astrobiology he did talk to “quite a few creationists,” as well as to the Vatican, and found that “virtually all leaders of religion,” primarily Christianity in this case, say “no problem.” Creationists, on the other hand, told him that finding intelligent life elsewhere would be impossible under Christianity. As the conversation with the audience continued, Pappalardo said that the discussion was at the “boundary of the triple junction among science, religion, and philosophy.” He related that when he asks his students to privately write down whether finding other life would affect their religious beliefs and do 27

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they think it would affect others’ beliefs, he was surprised to find that most say it would more solidly establish their religious beliefs while the beliefs of others would change. Kaufman asked Seager and Benner if there is a “moral/transcendent component” to their work. Seager replied no, that she wants to find other Earth out of “sheer curiosity.” Benner also said no, explaining that “we are part of this grand experiment that is going from the slime to . . . maybe the entropic death of the universe. We are part of this grand experiment. . . . Morality is a separate thing entirely. I don’t kill puppies or steal people’s belongings.” In closing, the group had a brief discussion about how Hollywood deals with science in the context of entertainment. Seager commented that real science does not sell, and “even if Hollywood really knows” the science being depicted is wrong, that does not mean they will not make the movie, as the film 2012 demonstrates. Pappalardo closed by noting that it was Carl Sagan’s birthday that day and “we can reflect on his extremely effective communication style.” Sagan’s zest for the search for life infused much of his work and his teaching, Pappalardo said, so in thinking about how to communicate with the public about the Grand Questions, Are we alone? is the grandest of them all and can be a way to engage them. 28