NEWS IN FOCUS

of scientists on topics that include health, climate agreement. Trump, who has long — which Obama kick-started in 2008 — risks education and the environment. denied mainstream climate science, also said further polarizing thorny policy debates around “Trump doesn’t have a prominent policy that his administration will focus on “real envi- scientific issues such as global warming. “The shop and a prominent set of policy advisers,” ronmental challenges, not phony ones”. Democrats found that science was a good thing says Douglas Holtz-Eakin, who counselled for them, just like historically strong support for Republican senator John McCain (Arizona) on SPLIT TICKETS the military was good for the Republicans,” says economic policy during his failed 2008 presi- This yawning philosophical divide is apparent Daniel Sarewitz, co-director of Arizona State dential bid. “Clinton has a vast bureaucracy in the party platforms that the Republicans and University’s Consortium for Science, Policy and a ten-point plan for going out to lunch, so Democrats developed ahead of their nominat- and Outcomes in Washington DC (and a regu- they couldn’t be more different.” ing conventions this month. Environmental- lar contributor to Nature). “If the Democrats are The two candidates — whose campaign ists have criticized the Republican platform the party of science, and you are a Republican, staff declined multiple interview requests for labelling coal a “clean” energy source, even what does that make you think?” — also seem to think very differently about though it produces But Holtz-Eakin says that the Trump cam- the role of science. Although Clinton has “Climate is more carbon dioxide paign’s apparent decision to forgo science described science and innovation as a foun- going to be emissions per unit of advice is a reflection of Trump himself, not dation for the future, science funding seems talked about in energy than any other of Republican priorities. In 2008, he notes, to be an afterthought for Trump, says John this campaign.” fossil fuel. Demo- the McCain campaign consulted scientists to Karsten, coordinator of the Center for Tech- crats, meanwhile, are formulate its positions on issues such as global nology Innovation at the Brookings Institu- poised to adopt a platform this week at their warming — just as Clinton has done. tion, a think tank in Washington DC. Instead, national convention that calls for using “every With just over three months until the elec- the Republican has focused on issues such as tool available to reduce emissions now”. tion, there is still a chance that Trump will national security, immigration and crumbling “Climate is going to be talked about in assemble his own coterie of science advisers, infrastructure. this campaign, because the candidates have says Andrew Rosenberg, who heads the Center Climate change is one of the few science distinctly different positions,” says Michael for Science and Democracy at the Union of topics that has grabbed the campaign spotlight Oppenheimer, a climate scientist at Princeton Concerned Scientists in Cambridge, Mas- — in part because of Republican anger over University in New Jersey who is advising the sachusetts. Doing so not only informs policy Obama’s regulations to limit greenhouse-gas Clinton team. Although his workload was light positions, it builds relationships that are useful emissions from power plants, vehicles and oil during primary season, Oppenheimer antici- after the election, when the winning candidate and gas development. Clinton’s climate and pates questions from the campaign about how begins to assemble a government. energy proposals would largely maintain the global warming might affect certain regions, or “These things widen the network,” Rosen- current course; by contrast, in a major policy the extent to which an extreme weather event berg says. “I know it’s happening with the speech on 26 May, Trump promised to roll might be related to global warming. Clinton campaign, and at some point I would back Obama’s “totalitarian” regulations and Some experts say that the Democratic expect it would happen with the Trump withdraw the United States from the Paris party’s adoption of science as a campaign issue campaign.” ■

ASTRONOMY How to hunt for alien life Astrobiologists try to determine the chemical signature of life on other worlds.

BY ALEXANDRA WITZE how to avoid embarrassing errors in the future. planet,” says Sarah Rugheimer, an astronomer “We have to come together and determine at the University of St Andrews, UK. n the search for life beyond Earth, false what good evidence of life on another planet Detecting a biosignature gas is just the first alarms abound. Researchers have gener- could be,” says Shawn Domagal-Goldman, one step to understanding what could be happening ally considered, and rejected, claims rang- of the workshop’s organizers and an astrono- on an exoplanet. Each world has its own combi- Iing from a 1970s report of life on Mars to the mer at NASA’s Goddard Space Flight Center in nation of physical and chemical factors that may 1990s ‘discovery’ of fossilized space microbes Greenbelt, Maryland. or may not lead to life, says Victoria Meadows, in a meteorite. The exercise comes at a crucial time, as an astronomer at the University of Washington Now, inspired by the detection of thousands astronomers grapple with how to interpret in Seattle. “Planets are hard, and we shouldn’t of planets beyond the Solar System, NASA has exoplanet data from the next generation of think they are all going to be the same or reveal started a fresh effort to learn how to recognize tele­scopes. Some scientists are working to their secrets very easily,” she says. extraterrestrial life. The goal is to understand understand how nature could produce arche- A planet’s environment is key. Some Earth- what gases alien life might produce — and how typal biosignature gases, such as oxygen, in the sized planets orbit M dwarf stars — the most Earth-bound astronomers might detect such absence of living organisms. Others are trying common type of star in the Galaxy — at the ‘biosignatures’ in light passing through the to think as expansively as possible about the right distance to harbour liquid water. But atmospheres of planets trillions of kilometres types of biochemistry that could sustain life. Meadows’ collaborators have shown1 that away (see ‘Searching for alien life’). “We could fool ourselves into thinking a photo­chemical reactions can send water into The agency will convene a workshop this lifeless planet has life — or we could be miss- the planet’s atmosphere and then break off its week in Seattle, Washington, with the ultimate ing life because we don’t really understand the hydrogen, which escapes into space. What’s left goal of advising a NASA exoplanet group on context of what could be produced on another is a thick blanket of oxygen that might seem as

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IN FOCUS NEWS

alternative biosignature gases — things not as obvious as oxygen that might be made by organisms under certain conditions. These SEARCHING FOR ALIEN LIFE include dimethyl sulfide3, which is produced Astrobiologists are ne-tuning the list of substances that, if spotted on a planet 4 orbiting another star, could constitute evidence of extraterrestrial life. by Earthly phytoplankton, or even ammonia . On a cold alien planet, organisms might make LIFE AS WE KNOW IT LIFE AS WE DON’T the gas using the same chemical process as

E1500047 (2015); CONE: REF. 5 E1500047 (2015); CONE: REF. One method is to study a star’s light for Another approach is to evaluate a industrial manufacturers. 1, the chemical imprint of gases that may huge range of molecules, winnowing have been formed by living organisms. them down on the basis of factors At the Massachusetts Institute of Technol- such as stability and detectability. ogy in Cambridge, astronomer Sara Seager has SCI. ADV. begun to examine 14,000 compounds that are All small Oxygen Ozone Ammonia molecules stable enough to exist in a planetary atmos- phere. She and her colleagues are winnowing down their initial list of molecules using crite- ria such as whether there are geophysical ways Methane Sulfur 5 compounds to send the compound into the atmosphere . “We’re doing a triage process,” says Seager. “We don’t want to miss anything.” The Seattle meeting aims to compile a work- SOURCE: CHART: S. SEAGER & W. BAINS S. SEAGER SOURCE: CHART: ing list of biosignature gases and their chemi- cal properties. The information will feed into how astronomers analyse data from NASA’s James Webb Space Telescope, slated for launch Changes in the starlight transmitted through in 2018. The telescope will be able to look at the planet’s atmosphere reveal gases within. only a handful of habitable planets, but it will provide the first detailed glimpse of what gases surround which world, says Nikole Lewis, an Venus ) 6 astronomer at the Space Telescope Science

–10 CH4 H2O Warm mini- Institute in Baltimore, Maryland. 10

× Neptune No single gas is likely to be a slam-dunk 4 indicator of alien life. But Domagal-Goldman CH4 H2O hopes that the workshop will produce a frame- O2 H2O Super-Earth work for understanding where scientists could 2 trip themselves up. “We don’t want to have a Earth great press release,” he says, “and then a week Archaean Earth ■ Planet ux/star ux ( 0 later have egg on everybody’s faces.” Possible 0.4 0.5 0.6 0.7 0.8 0.9 1.0 biosignature 1. Luger, R. & Barnes, R. Astrobiology 15, 119–143 Wavelength (µm) gases (2015). 2. Schwieterman, E. W. et al. Astrophys. J. 819, L13 (2016). 3. Domagal-Goldman, S. D., Meadows, V. S., Claire, M. W. if it came from living organisms, but results molecules collide to produce O4. So spotting from a run­away greenhouse effect. O in a planet’s atmosphere could be a clue that & Kasting, J. F. Astrobiology 11, 419–441 (2011). 4 4. Seager, S., Bains, W. & Hu, R. Astrophys. J. 775, 104 There are ways to tell. The runaway green- the oxygen does not, in fact, come from life, (2013). 2 house would create an atmosphere thousands Meadows’ team reported this year . 5. Seager, S., Bains, W. & Petkowski, J. J. Astrobiology of times denser than Earth’s, in which O2 Another method is to draw up a list of 16, 465–485 (2016).

EPIDEMIOLOGY Brazil’s birth-defects puzzle Zika virus might not be only factor in reported microcephaly surge.

BY DECLAN BUTLER northeast. Although evidence suggests that it could change researchers’ assessment of the Zika can cause microcephaly, the clustering risk that Zika poses to pregnant women and overnment researchers in Brazil are set pattern hints that other environmental, socio- their children. to explore the country’s peculiar dis- economic or biological factors could be at play. The idea has long been on Brazilian research- tribution of Zika-linked microcephaly “We suspect that something more than Zika ers’ radar, but the enquiry marks the first time G— babies born with abnormally small heads. virus is causing the high intensity and sever- that scientists at the health ministry have taken Zika virus has spread throughout Brazil, ity of cases,” says Fatima Marinho, director up the hypothesis. The ministry has asked but extremely high rates of microcephaly of information and health analysis at Brazil’s Oliver Brady, an epidemiologist at the London have been reported only in the country’s ministry of health. If that turns out to be true, School of Hygiene & Tropical Medicine,

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