Other Worlds: The Search for Life in the Universeby Michael D. Lemonick, Michael Lemonick
Are we, or are we not, alone?
In this tour de force of popular science writing, Michael D. Lemonick describes the fascinating search to discover the answer this intriguing question. Recent events including speculation that life may have existed on Mars and the discovery that there are more planets outside our solar system than in it /b>… See more details below
Are we, or are we not, alone?
In this tour de force of popular science writing, Michael D. Lemonick describes the fascinating search to discover the answer this intriguing question. Recent events including speculation that life may have existed on Mars and the discovery that there are more planets outside our solar system than in it continually spur new theories and new investigations.
Other Worlds takes readers to Mauna Kea, where astronomers monitor the skies through powerful telescopes; to West Virginia, where radio antennas listen for alien broadcasts; and to meetings with NASA officials, who are forging new paths in the exploration of the cosmos. Featuring interviews with the scientists who are leading these breakthroughs, this astonishing book will captivate everyone from science-fiction buffs to serious science readers.
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Paul Butler sits at his desk, utterly still. He's transfixed by the image displayed on the computer in front of him. The screen shows a field of dots. To the untrained eye, they seem utterly random, like flecks of black pepper sprinkled on a sheet of white paper. They look that way to Butler's exquisitely trained eye as well. He's usually very good at spotting patterns in data like this; the hidden shapes tend to jump right out at him. This time, however, if there is order underlying the apparent chaos, it's beyond him and therefore probably beyond the capacity of any human being.
He has a software program, though, that can make sense of this mess, provided that there is any sense to be made. What Butler hopes assuming that the last eight years of painstaking, frustrating, rarely appreciated work has not been a complete waste of time and that nature will cooperate, which is by no means guaranteed is that the dots will fall along a curve. He doesn't know exactly what this curve will look like, but broadly speaking, it should snake from left to right, rising toward the top of the screen, then falling gracefully to the bottom, then rising again, over and over. It should resemble, in a very rough way, the reassuringly regular pulse of a healthily beating heart displayed on the cardiac monitor of a hospital coronary care unit. Most important of all, the curve should pass through just about every one of the dozens of spots on the screen, linking them together as though this were an incredibly difficult connect-the-dots game whose picture is impossible to pick out in advance.
If the curve exists, concealed in the data, his software will beable to find it and trace it for Butler's merely human eyes. He was here very late last night, looking at screen after screen of data for such a tracing, plugging new information into the computer, scanning the results, moving on to the next data set. His colleague and mentor Geoffrey Marcy like Butler an astronomer with joint appointments at San Francisco State University and the University of California, Berkeley was working alongside him until midnight. By two in the morning, Butler, too, had to quit. He got on his bike and pedaled back to his tiny apartment in the south Berkeley ghetto (his own description of the neighborhood).
Now, only six hours later, he is back at the task that has consumed him for the past two months. While Butler slept, the software was patiently searching for that elusive perfect fit, a curve that would slice neatly through most of the dots on the screen. It has tried fat curves and skinny curves, examining each one and discarding it when too many dots were left floating, unanchored.
The program finished its calculations a few minutes ago. Butler is looking at the result. There is the line, as lusciously curvaceous as the illustration in a textbook. Every dot on the screen is sitting right on the line or very close to it. No stragglers. This is precisely the pattern Butler has been aching to see. And now that he is looking at the squiggle that has haunted his dreams since he began this project eight years ago, all he can do is stare. The Berkeley campus is slowly coming to life on this winter Saturday morning, but Butler is completely unaware of it. He hears nothing, feels nothing, sees nothing but the glow of a cathode-ray tube bearing news that will forever change humanity's understanding of where it stands in relation to the cosmos.
The dots on Butler's computer screen mark observations of 70 Virginis, a star quite similar to the Sun in mass and age and temperature pretty much a garden-variety G star, according to the arcane classification scheme astronomers use. The star 70 Vir lies in the constellation Virgo and is perhaps thirty-five light-years away from Earth two hundred trillion miles, more or less.
The graph on Butler's computer screen represents 70 Vir's motion in relation to our own solar system, plotted over several years. If a dot appears at the top of the screen, that means the star is moving toward us. If a dot shows up at the bottom, it's moving away. The fact that every dot in Butler's plot falls on a perfect curve, though, means that 70 Vir is moving both toward and away from Earth first the former, then the latter, in a rhythm that repeats itself every 117 days. 70 Vir is wobbling.
It's no surprise to discover that a star is moving. Every star we can see is moving as it orbits in an enormous, lazy circle around the pinwheel-shaped Milky Way galaxy. They're all like horses on a merry-go-round that measures one hundred thousand light-years, or about six hundred quadrillion miles, across. Unlike the horses on a carousel, though, the stars are not bolted in place. Each star orbits independently, following its own unique path through the heavens. It's true that the stars appear to be unmoving: The constellations, Virgo included, look precisely the same tonight as they did last night, and a hundred years ago, and a thousand. But that's really an illusion created by the fact that the stars are incredibly far away and that we're all moving in about the same direction at about the same speed.
Not precisely, though. Every star is constantly being affected by the combined gravity of hundreds of its neighbors as well as the gravity of huge clouds of interstellar gas. The stars are actually weaving in and out as they go, in a slow dance, essentially imperceptible due to the vast distances between them. Tens of thousands of years from now, the constellations that Chinese and Arab astronomers knew intimately and that we in the Western European tradition still call by their Greek and Latin names will have lost their shapes and taken on new ones.
For the very closest stars, astronomers can actually measure these gradual motions. The fastest-moving star on record, Barnard's Star, shifts its position by about one two-hundredth the width of the full Moon each year. Astronomers have been making such delicate measurements for many decades. But the path a given star traces across the sky should be smooth, not bumpy. It should, that is, unless something is yanking on the star. Outside the solar system, the Sun's motion would be bumpy because the Sun has planets orbiting around it. The planets are relatively puny; even Jupiter, by far the biggest, is only one one-thousandth as massive as the Sun. Still, their gravity is enough to have a small but distinct effect. From a light-year or two away, the planets themselves would be invisible, but their presence especially that of Jupiter could be inferred from the wobbling of the Sun.
Now Paul Butler is looking at 70 Vir. The computer is telling him that 70 Vir is wobbling. Of course, the computer's opinion is only as good as the data it has to work with. Butler and Marcy are the ones who made the telescopic measurements of 70 Vir's position over the years. They designed and built some of the instruments they used. Butler wrote much of the software for his data analysis thousands upon thousands of lines of arcane programming language. If the computer is wrong, it isn't the computer's fault.
Butler and Marcy are extremely careful scientists, though. They've tried to think of every conceivable way they might be fooling themselves, and there are many. They know that if they can find planets circling stars beyond the Sun, they'll earn tremendous respect from their colleagues, public acclaim, and perhaps most important a flow of research funding to keep their work going. They know equally well that if they announce a discovery that turns out to be wrong, they'll be cited in basic astronomy texts for the next fifty years as examples of how not to do science.
So they've tried to be harder on themselves than any critic in this extraordinarily competitive field would ever think of being. They've second-guessed themselves at every turn and are convinced they've eliminated every source of self-deception that might exist. The dots are so beautifully studded along the curve that Butler can see right away this is what scientists call a forty-sigma detection. "It was roughly as unmistakable," Butler would say later, "as an atomic bomb blast."
A forty-sigma detection means that the wobble they've measured in 70 Virginis's position is forty times as large as the uncertainty in the measuring technique. "Most cutting edge detections in science," Butler would explain, "are of the three-sigma variety. If the size of the signal you are looking for is only three times the size of your errors, the detection is only marginally believable." It's as if you had a speedometer that was accurate only to within 20 miles per hour. The speedometer might read 60 when you were actually going anywhere from 40 to 80. With a three-sigma speedometer, you'd be a fool to feel secure while zipping past a police car. With a forty-sigma speedometer, on the other hand, a reading of 60 would mean you're going between 581/2 and 611/2. You could be pretty sure of yourself telling a cop you were doing 60. If the astronomy police pulled Butler over right now, he'd be on safe ground. There appears to be no other plausible interpretation of what he is seeing: 70 Vir is not alone in space.
"My mind simply shut down," he will say a few months later when things have finally begun to return to normal. "Archimedes jumped out of the bathtub and ran naked through the street shouting 'eureka.' But I just sat there, dumbfounded. Nobody was around. I'd blink, and it was still there. I couldn't move. I could only turn my head."
After about an hour, the phone rings. His girlfriend, Nicole, wants to know what's up. He can barely speak a coherent sentence. After she hangs up, it occurs to him that he should let Geoff Marcy know what has happened. The two astronomers have gotten to be good friends, working together for almost nine years, but given the long hours they both put in, they're very respectful of each other's off-duty time. Butler hates to disturb Marcy at home. He does it anyway.
At his house in Berkeley, Marcy is heading out the door with his wife, Susan, when the phone rings. They're on their way to buy supplies for a New Year's Eve party the next night. He hears Butler say, in the most serious tone of voice Marcy has ever heard him use, "Geoff, get over here." Then silence. Marcy has to pry the information from him. "What is it, Paul? Have the computers been stolen? No? Is the building on fire?"
After several minutes of trying, the most he can get from Butler is that the news is good. "Come now" is all Butler can manage to say. So Geoff and Susan drive over to campus, burst into the office, and find Butler still looking at the screen. The data are still up on the computer. Marcy looks for approximately a second, then says, "Oh, my God."
Kathie Thomas-Kaperta has a decision to make. She's supposed to present a paper at the annual Lunar and Planetary Science conference, where researchers will gather from all over the world to talk about and listen to and argue over the latest results on everything from newly discovered comets to lightning on Jupiter to the moons of Uranus. Thomas-Kaperta's paper has an innocuous enough title: "Microanalysis of Unique Fine-Grained Minerals Within the Martian Meteorite ALH84001." What it says is that Thomas-Kaperta, a geologist with the Lockheed-Martin Company's space science division, has used a powerful device called a transmission electron microscope to peer inside a slice of rock thinner than a piece of paper. Her purpose is to understand, on a very detailed level, exactly what it's made of.
The word "Martian" isn't a mistake, nor is it meant to be taken metaphorically. This rock, about the size of a potato and weighing a little over four pounds, comes from the planet Mars. It's one of twelve meteorites on Earth that planetary scientists are convinced came originally from the surface of the red planet. Their mineral and chemical composition is unlike anything on Earth or the Moon or even the asteroids and comets, where most meteorites came from. But they match nicely the chemistry of Mars, a chemistry that was studied directly during the Viking missions of the 1970s.
The meteorites come from Mars, but they were all found on Earth in Egypt, France, India, and mostly Antarctica, which is where Thomas-Kaperta's specimen showed up. They dropped out of the sky, the victims of a highly improbable set of circumstances that was nevertheless repeated several times: Asteroid smashes into Mars; debris is blasted into interplanetary space; some eventually wanders into the gravitational influence of Earth and falls to the ground.
Naturally, these meteorites are valuable commodities. NASA is still years away from bringing back a single molecule from Mars for study, but here, in the form of these rocks from space, are pounds and pounds of Martian matter. Dozens of scientists in labs all over the world are looking at the Mars meteorites, performing every test they can possibly think of to understand what makes Mars tick. Thomas-Kaperta is one of them, and now she's ready to report on her findings.
What she's found inside ALH84001 is a bunch of tiny crystals crystals so small that five million of them laid side by side would form a line just one inch long. The crystals are magnetite, a magnetic mineral made of oxygen and iron. Magnetite is reasonably common on Earth and quite familiar to geologists. It's also familiar to biologists. Magnetite forms naturally inside the bodies of certain living organisms, notably migratory birds and water-dwelling bacteria. Its function is navigational: Armed with magnetite, organisms can sense the direction and intensity of Earth's magnetic field and use the information to find their way to an old nesting ground or a new source of food. The birds and bacteria come equipped with an internal compass.
Magnetite can form outside living organisms as well, but when that happens, it doesn't tend to look like the tiny, cubical, and teardrop-shaped crystals that are typical of biological magnetite. The crystals in the ALH84001 are tiny cubes and teardrops.
That's not all Thomas-Kaperta has found. There's another magnetic mineral, a form of iron sulfide known as gregite, inside the meteorite. Like magnetite, gregite occurs inside the bodies of bacteria; like magnetite, it's there for use as a biological compass. It, too, can form nonbiologically, but again, the particles of gregite in Thomas-Kaperta's sample look precisely like what you'd expect to find inside a bacterium.
So in the abstract for her paper the one-paragraph summary that helps colleagues figure out which presentations sound interesting Thomas-Kaperta ended with: "This is suggestive of biogenic activity." She was saying it looked as though something had lived inside this meteorite when it was still on Mars.
Now she's worried, and so are the other scientists working with her on this project. Thomas-Kaperta is about to go before her professional colleagues and suggest that she has evidence for life on Mars. What's worrying her is not the obvious, however. She isn't afraid she'll be laughed off the stage or lampooned in the media. Like Paul Butler and Geoff Marcy, Thomas-Kaperta is an extremely careful scientist. She second-guesses herself at every step, looks for ways she might be fooling herself. She knows that uttering the words "life on Mars" is something you don't ever want to do, even with the word "suggestive" in front of it, if you're not sure of what you have. But she also knows magnetite when she sees it, she knows gregite, and she knows that her conclusion is scientifically supportable.
Thomas-Kaperta is therefore not worried about her reputation; she's worried about her timing. Her microscopic searches are one part of a larger, ongoing project to characterize this Mars meteorite, one line of detective work in an investigation that has proceeded on many fronts. The work has been going on for nearly two years, and it's finally starting to come together. If she steps forward now, she could blow the whole deal. The team is already nearly finished with a major research paper, pulling together the combined conclusions of nine scientists in what they believe will be a powerful case.
But it's crucial, they believe, to publish their paper in the most reputable scientific journal they can. Reasonable or not, their assertions will be widely challenged. They want every bit of credibility they can get on their side. So they're aiming for Science, the unassailably prestigious weekly journal of the American Association for the Advancement of Science. If any part of their paper appears somewhere else first, though in the published proceedings of a Lunar and Planetary Science conference, for example, or in a newspaper or popular magazine Science will declare it old news and refuse to publish it.
Thomas-Kaperta hasn't considered that problem before. Neither have her partners. Now that they do, they realize they have only one choice. Thomas-Kaperta contacts the conference organizers and withdraws her paper. Other scientists who notice the abstract in the program will note her withdrawal; some of them undoubtedly will wonder whether the research was shaky, or whether she yanked it because she had lost confidence in her results. It won't be long before they learn otherwise.
It's ten o'clock at night in Mountain View, California, when the phone rings in Seth Shostak's bedroom. He answers and hears the voice of his boss, Tom Pearson. Normally, the last person you want to find on the other end of the phone at that time of night is your boss. And, indeed, Pearson's news is disturbing, although it has nothing to do with Shostak's employment status. Seth Shostak works at the SETI Institute SETI being an acronym for the Search for Extra-Terrestrial Intelligence. Pearson has just received a phone call from Australia where the institute's flagship program, known as Project Phoenix, is currently based.
Like all SETI programs, Phoenix is an attempt to listen for the radio signals broadcast by alien civilizations. No one knows whether such civilizations exist or whether they use radio waves for communication. But if they do and we aren't listening, we'll miss one of the most important discoveries in history. So we're listening not spending a lot of money, since it's a long shot, but listening nevertheless.
If Paul Butler and Kathie Thomas-Kaperta need to be extremely careful about reaching premature conclusions and to be vigilant to the dangers of fooling themselves, Shostak and other SETI researchers need to be even more careful. It's one thing to claim prematurely that you've detected a planet or found evidence "suggestive" of submicroscopic life; it's quite another to say you've just heard from E.T. The former might earn you condescending sympathy from your colleagues, but the latter will make you a laughingstock. SETI is a perfectly legitimate branch of astronomy. It does, however, have an inherently high giggle factor that has to be kept constantly at a minimum.
That's why Project Phoenix was designed with multiple anti-giggle backup systems and why Shostak finds his boss's call so disturbing. The 210-foot radio telescope at Parkes Observatory in Australia, Phoenix's primary listening antenna, has picked up a promising signal. That's no big deal; all sorts of things can masquerade as an alien broadcast. A satellite passing overhead, a radar beam from a nearby airport, a radio broadcast from Sydney bouncing off the ionosphere at an unlucky angle, or any one of a hundred other human-generated signals will do.
When a signal does come in, the Phoenix computer tells a second radio telescope several hundred miles away to take a look. Most of the time it sees nothing; the signal is very local and clearly not alien. Once or twice a week, though, the second telescope sees it, too. That still doesn't prove anything; plenty of human signals have enough range to trigger two widely separated telescopes. When that happens, Phoenix scientists go to the next step in their self-debunking process: They aim the main radio dish away from whatever star they've been pointing at. If the signal is still coming in, it's not coming from the star and is thus almost certainly not coming from a distant solar system.
Tonight, though, the signal at Parkes has passed not only the first test the backup telescope sees it, too but also the second. When the telescope operators aim away from the star, the signal disappears. When they move it back, the signal comes back. Now they're trying a third test. In an hour the star will be setting below the horizon. If the signal winks out at the same instant, the coincidence will be too strong for any other conclusion: There is quite possibly a radio beacon aimed at Earth from another star system.
Shostak's wife is lying in bed reading, but he can't sit still and keeps pacing around the room. He has thought about the moment of contact for years how he would feel if it really happened, what he would do, how he would deal with the knowledge that we are not alone in the universe. He has talked it over in late-night bull sessions with other SETI researchers. Now that the moment may finally be here, he's mostly feeling disoriented and very, very nervous.
Finally, the hour is up. The phone rings. It's Tom Pearson again. The star has disappeared. The signal hasn't. They never will figure out what it was, but like all the other alarms SETI researchers have responded to over the past three decades, this one is false. But the next one may not be.
Step outside on a moonless, cloudless night and look up at the sky. If you're well away from any densely populated area, you can see several thousand stars without the help of a telescope or binoculars. Every one of them is a sun and, that being the case, it's almost impossible not to wonder whether one of them has planets that are home to intelligent creatures looking up into their own night sky and wondering.
Trying to figure out our place in the universe, our standing in the cosmic scheme of things, is probably as old an activity as walking. The question is one which all religions attempt to answer, and much of science as well. The more specific question of whether other beings inhabit distant worlds is at least as old as recorded history. The ancient Greeks actively debated whether the universe is home to other worlds and other life, as did medieval clerics and Renaissance philosophers and nineteenth-century scientists.
By 1995 the question had not been settled. Common sense certainly favors the idea that life must be everywhere. The Milky Way contains billions of G-type, Sun-like stars. It's almost inconceivable that out of all these billions, ours is the only place where intelligence exists. But common sense has proven wrong in the past. If humanity is truly alone among the hundred billion stars of the Milky Way, which is itself one of tens of billions of galaxies in the universe, then the laws of Nature are indeed perverse but nowhere is it written that they must be otherwise.
If, on the other hand, there is intelligent life on a significant number of other worlds, humanity is almost certainly not the most intelligent, the most accomplished, the most anything. The law of averages essentially guarantees that we are mediocre. That in turn leads to all sorts of speculations about what might happen if we ever come into contact with extraterrestrials. Perhaps we'd be in horrible danger. Perhaps we'd be able to tap into the eons-old knowledge of other galactic civilizations to learn the answers to questions we can't even formulate yet. Both possibilities have been thoroughly explored, of course, in science fiction books and movies. E.T. and Independence Day are perhaps the most memorable recent examples.
Without hard data, though, the question of humanity's place in the universe is purely a philosophical one. Unencumbered by the facts, you can take either side of the question and present convincing arguments both for and against the existence of intelligent alien life. And until 1995 there were essentially no facts. Nobody knew for sure that Sun-like stars had planets orbiting them, and without planets, it's hard to imagine life. Even if planets existed, nobody could say for sure whether the emergence of life, given the right conditions, was wildly improbable or nearly inevitable.
Yet after decades, centuries, millennia without actual information, it has suddenly and dramatically begun to flow. Paul Butler and Kathie Thomas-Kaperta and their collaborators and competitors are at last beginning to provide real data that other scientists can pore over. It isn't much so far. Butler is talking about a planet, not a galaxy filled with planets; Thomas-Kaperta is talking about microbes, not Vulcans like Star Trek's Mr. Spock. Inferring the existence of actual walking-around (oozing around?) aliens from these meager data requires a long chain of reasoning that could break at any point.
The chain of reasoning has a name. More than three decades ago, Frank Drake then a young radio astronomer and now an eminent scientist and also the president of the SETI Institute boiled the whole thing down to an equation that became known as the Drake equation. In prose form the equation says that the number of civilizations theoretically detectable at a given time depends on how many stars there are, how many of those have planets, how many of those are hospitable to life, how many of those give rise to life, how many of those give rise to technological civilizations, and, finally, how many of those survive their own success. This last point is extremely important. If the average high-tech civilization blows itself up after fifty or one hundred years, we probably won't ever get to talk to anyone.
The Drake equation is so concise and so apt a statement of the extraterrestrial intelligence problem that nobody has ever come up with a better way of stating it. Researchers in a wide range of fields biologists thinking about the origin of life, astronomers trying to tease the faint signature of other worlds out of the motions of nearby stars, theoretical astrophysicists trying to unravel the mysteries of planet formation can and often do describe their work as an attempt to crack part of the Drake equation.
In that sense, Butler's and Thomas-Kaperta's research, though preliminary, is extraordinarily important. Butler's observations don't yet tell astronomers how many stars have planets around them, but they at least prove that some beyond the Earth do. Thomas-Kaperta's work doesn't prove that life is common throughout the Milky Way, but it makes that proposition far more convincing.
Not everyone will be convinced, of course, even by the most rigorous scientific research. Some astronomers will suggest that Butler's planets aren't really planets after all; many biologists will question whether Thomas-Kaperta's team has found evidence of life or simply of something that looks like life. Dealing with their critics will probably take as much time as the original research, and more. "That's what we expected," says Everett Gibson, a NASA geologist who works with Thomas-Kaperta. "That's the way science is supposed to work. You go out there with your best evidence and hope that your critics haven't thought of something you didn't anticipate."
While the critics take their best shots at undermining these first apparent breakthroughs in solving the Drake equation, the scientists working on planet searches and microbes from Mars and SETI programs and a dozen other related research programs are moving on. The discoveries of Butler and Thomas-Kaperta and their colleagues are a beginning, not an end. Even as the scientists announced their shocking results to an astonished world, they were digging deeper into their data and trying to gather more. Before the year is over, Butler and Marcy will have more than 70 Virginis to talk about, and they'll take their observing program to the most powerful telescopes on Earth to probe deeper into the Drake equation. By early in 1997, Thomas-Kaperta's group will claim new, more powerful evidence for life in their Martian meteorite.
And they won't be alone. Marcy and Butler are the most prolific planet-hunters in the world, but they are not the only ones. Thomas-Kaperta's group has learned more than anyone else about what's hidden inside the Martian meteorite ALH84001, but ALH84001 is not the only Martian meteorite on Earth, and hers is not the only team looking for signs of life. In science as in sports, proving that a difficult feat is nevertheless possible makes it easier, suddenly, for others to repeat it.
Within a few months after Butler's startling discovery, that is precisely what will happen, and Drake-equation science will become the focus of just about every major astronomical and general science conference. While the astronomers talk of new planets and the meteorite analysts discuss the fine structure of Martian rocks, biologists will offer their own insights into the origin of life; planetary scientists will find powerful new justification for sending space probes back to Mars and even out to the moons of Jupiter; and instrument designers will be laying out their plans for giant new telescopes that will make the Hubble Space Telescope and the Keck Observatory look small and old-fashioned. Today, the best Paul Butler can do is see evidence that a star is wobbling; within a decade or two he may be able to see Earth-like planets directly and even probe their atmospheres for telltale signs of life.
SETI researchers like Seth Shostak, meanwhile, will be looking to the skies with new encouragement: There are planets out there after all, and there may be, or may once have been, life on Mars. So they'll be continuing their own campaign to make the planet-hunters' work obsolete. They will bring Project Phoenix from Australia to a new, semipermanent home at the National Radio Astronomy Observatory in Green Bank, West Virginia, and help fund a handful of smaller projects around the world.
And while they assume their search will take years at least, and probably decades, it's also true that an alien radio broadcast could be sweeping across Earth as these words are being written or being read. Long before a post-Hubble Space Telescope takes pictures of an alien Earth, the question of whether other civilizations populate the universe may be solved in one single, dramatic message from the stars. Either way, the ancient mystery of life in the universe has finally, after uncounted thousands of years, begun a transformation from a religious, philosophical, purely intellectual question to a scientific one. Soon quite possibly within a decade or two it may be solved.
Copyright © 1998 by Michael Lemonick
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