The Asteroid Hunters

The Asteroid Hunters

February 15, 2013: A 17-meter asteroid explodes over Russia releasing the energy equivalent of 500 kilotons of TNT. - NASA

It's highly unlikely that a gigantic space rock will crash through our atmosphere and destroy civilization as we know it. But it's not impossible either. Which is why a small but growing community of scientists and astronomers are scrambling to spot and destroy dangerous asteroids long before they hit us.

By Josh Dean

On August 18, 2015, an otherwise unexceptional summer Tuesday, NASA issued a press release titled "There is No Asteroid Threatening Earth." This was an alarming headline to stumble upon if you had no idea that people out there were actually concerned that an asteroid might threaten Earth soon — so concerned, in fact, that their agitating and blog writing forced the world's most respected space agency to issue an unequivocal denial.

"Numerous blogs are erroneously claiming that an asteroid will impact Earth, sometime between Sept. 15 and 28, 2015," the release stated. "There is no scientific basis — not one shred of evidence — that an asteroid will impact Earth on those dates," declared Paul Chodas, manager of NASA's Near-Earth Object (NEO) office at the Jet Propulsion Laboratory in Pasadena, California. In fact, the release continued, NASA's Near-Earth Object Observations Program "says there have been no asteroids or comets observed that would impact Earth anytime in the foreseeable future."

It seemed, out of context, like something from the Onion. Incredible rumors often arise, but rarely do they gain enough credence that the head of a national scientific office sees fit to comment, and then issue a press release. But such is the curious and little understood world of planetary defense, wherein a small but growing community of scientists study and prepare for the possibility that a chunk of rock from space could plunge through our atmosphere and strike the Earth, causing wanton destruction.

 

There's precedent for worry. On the morning of February 15, 2013, residents of Chelyabinsk, Russia, were just waking up when a streak of intense light appeared from the east and ripped across the horizon before exploding. At first, people suspected a missile, possibly nuclear. But it was an asteroid.

The object was approximately 17 meters in diameter, traveling 42,000 miles-per-hour and, thanks to atmosphere drag, it burned up and detonated high above the ground. Scientists call this an airburst, and the explosion shattered windows, collapsed walls, damaged roofs, and injured more than 1,500 people, most from flying glass. At its most intense, light from the exploding object was 30 times brighter than the sun, causing some locals to experience retinal and skin burns. A few chunks of rock made it to the ground — including a boulder-sized piece that crashed through the ice of a frozen lake — but 99 percent of the asteroid vaporized in mid-air, releasing the energy equivalent of 500 kilotons of TNT.

"Every night, tiny pieces of rock enter our atmosphere and burn up. We call them shooting stars."

Every night, tiny pieces of rock from space enter our atmosphere and burn up. We call them shooting stars. Typically, they're no larger than basketballs and often they're much smaller, on the order of grains of sand, but periodically — and without warning — larger pieces arrive. Over a 20-year period from 1994 to 2013, the U.S. government recorded 556 instances of small fireballs, known as "bolides," caused by asteroids exploding over the Earth's surface. The vast majority occurred over oceans, and went unseen. What made the Chelyabinsk Event so unusual was that it was a rare instance of a sizable chunk appearing over a population center in broad daylight — and it was captured on film, by dozens of cameras mounted on the dashboards of Russian cars. That made it extremely real.

And it wasn't modern Russia's first encounter with space debris. On June 30, 1908 — again, early in the morning — an asteroid ripped through the sky and exploded with tremendous force over an area of Siberian taiga near the Tunguska River. There were no humans in the immediate vicinity, but a man sitting on the porch of a remote trading post 40 miles away would later report that he was blown out of his chair and felt a heat so intense that he thought his clothes were on fire. It wasn't until 19 years later, in 1927, when a scientific expedition through the rugged forest led by the chief curator of the meteorite collection at the St. Petersburg museum — making his second attempt — finally reached the site and found 800 square miles of evergreen forest completely obliterated. More than 80 million trees had been knocked over, and lay in a radial pattern circulating out from the epicenter.

JPL-Caltech/NASA

"If you want to start a conversation with anyone in the asteroid business, all you have to say is 'Tunguska,'"

— Don Yeomans, NASA's Jet Propulsion Laboratory

The Tunguska asteroid was significantly larger than the one that blew up over Chelyabinsk. Scientists estimate that it was at least 120 feet in diameter, weighed 220 million pounds, and was traveling 33,500 miles-per-hour when it blew up in the lower atmosphere, releasing 185 Hiroshima bombs worth of energy. Barometers as far away as England sensed the shockwave and people who lived many miles from the site later reported seeing "the sky split in two" and a "great fire" appear, followed by a deafening boom. "If you want to start a conversation with anyone in the asteroid business, all you have to say is 'Tunguska,'" Don Yeomans, retired manager of the NEO Office at NASA's Jet Propulsion Laboratory (JPL), and a former colleague of Paul Chodas, has said.

 

It All Started With the Dinosaurs

 

The Tunguska asteroid would have leveled a large city and its surroundings. The example most often given is metropolitan London. But the threat of that actually happening in the near future isn't keeping anyone up at night. The occurrence of large asteroid impacts is rare, and the vast majority of the Earth's surface is unpopulated — with 71 percent covered by water — so even if a large asteroid should appear suddenly, the odds are it won't strike civilization. That said, science's view on asteroids has changed dramatically in the past few decades. We understand now that impacts are a regular facet of life in the solar system, and if you take the extremely long view, close encounters with objects far larger than Tunguska — asteroids that could obliterate regions or even wipe out humanity — are flying around out there and will eventually hit us, 500 or 10,000 or a million years hence.

The Tunguska asteroid leveled 7,700 square miles of Siberian forest in 1908.

Universal History Archive/Getty Images

That is, unless we locate these threats, study them, and make plans to mitigate them if and when necessary. The Chelyabinsk Event briefly got the world's attention. On Capitol Hill, the House of Representatives' science committee convened a hearing and called General William Shelton, Chief of the U.S. Air Force Space Command to explain, among other things, whether such an event could have been predicted. Shelton told the committee that this particular issue has been severely underfunded. What could we do, right now, the committee chair asked him. "The answer to you is, 'If it's coming in three weeks, pray,'" Shelton replied. "The reason I can't do anything in the next three weeks is because for decades we have put it off."

"The idea that one of those impacts could cause a mass extinction and redirect biological evolution—no one ever thought about that until the Alvarez discovery."

— Dave Morrison

This mission, to seek out threatening asteroids and prepare ways to deal with them, has become known as Planetary Defense, and you can trace its origins, more or less, to 1994, when the astronomy world watched in shock as the gigantic comet Shoemaker-Levy 9 broke into 22 fragments that, one after another, slammed into Jupiter. Each chunk hit Jupiter's atmosphere with a spectacular explosion, and left a scar in the planet's thick cloud layer larger than Earth. It was the first time humans had ever witnessed a collision between two solar system bodies. And had it been Earth instead of Jupiter, well, you wouldn't be reading this.

"That was a wake-up call," says David Morrison. "And it's no coincidence that the two big movies, Deep Impact and Armageddon, were released two years later." Morrison, a Senior Scientist at the NASA Ames Research Center in Mountain View, California, is the canary in the coalmine for the asteroid threat. You could tell the history of the movement through this one man with wire-frame glasses and hound-dog eyes. "When this conversation first started, the entire community could staff a single McDonald's" is a popular line in planetary defense circles. I heard it from three people. It's Morrison's quote. "I think it was one shift at one McDonald's," he clarifies, one afternoon in a dimly lit lounge at Ames. "I'm sure it's up to three by now."

What got Morrison's attention — way back in 1980 — was the so-called Alvarez Hypothesis, which provided a very credible solution to the long-standing mystery of what killed off the dinosaurs: It was a massive asteroid that struck Mexico's Yucatan Peninsula 65 million years ago. That asteroid was probably 10 to 15 kilometers in diameter and would have released one billion times the destructive energy of the atomic bombs that leveled Nagasaki and Hiroshima. It was so massive and struck the Earth with such velocity that it ripped 20 miles deep into the surface before exploding with so much violence that every living thing within thousands of miles was instantly vaporized. (It's been suggested that dinosaurs in Canada had about three minutes to live after that initial explosion.) What's more, the explosion blew massive amounts of vapor, earth, boulders, and fire into the atmosphere, blacking out the sky so that no sunlight reached the surface for two years.

Geologists and astrophysicists were long aware of craters caused by asteroid strikes, Morrison says. You can see them every night on the moon, and there are dozens of famous ones on Earth, including the mile-wide, 550-foot-deep Barringer Crater in Arizona. "But the idea that one of those impacts could cause a mass extinction and redirect biological evolution — no one ever thought about that until the Alvarez discovery."

The Barrington Crater near Flagstaff, Arizona is 570 feet deep and 3,900 feet across. It wasn't until 1960 when scientists confirmed it was caused by a meteorite, providing the first-ever definitive proof of an object from space impacting Earth.

Stephan Hoerold/Getty Images

Still, Morrison says, it was many years before the larger space community actually took the subject seriously, and plenty of colleagues remain skeptical. "For a long time one of our most common terms was the 'giggle factor,' because when you even said 'protection from an asteroid strike,' a lot of people dismissed it flatly." In 1988, Morrison co-wrote the book Cosmic Catastrophes, with the space scientist Clark Chapman, laying out the asteroid threat in clear but non-hysterical terms. The problem, it said, was solvable in principle. Three years later, Congress instructed NASA to study the impact hazard — a study chaired by Morrison — and then in July 1994, Shoemaker-Levy 9 made international news.

Finally, in 1998, Congress legitimized the issue. It mandated that NASA identify 90 percent of asteroids one kilometer and larger, because that was considered the rough threshold for an object that could basically destroy a large chunk of the planet, if not wipe out humanity altogether. At that time, there were maybe 50 known objects of that size. And the NASA "Spaceguard Survey" was established to begin filling in the gaps.

The survey was fairly simple and easy to execute. It used cameras attached to already existing Earth-based telescopes to photograph the night sky in search of bright objects that were clearly moving in relation to known stars. By 2005, that 90 percent goal had been met. And today, in 2015, there are more than 12,000 known Near Earth Objects (NEOs), all of them stored in a public database that includes other critical data, in particular their orbits.

Finding the civilization killers means that the space community has already significantly lowered the threat of global catastrophe. It doesn't mean that one of those huge asteroids won't intersect with Earth's orbit hundreds or thousands of years down the road, but it means we'll probably see it coming far enough in advance to do something. Unfortunately, that's hardly the only threat. "It's a huge step from saying there are none out there that are going to impact in the next century and cause a global catastrophe to saying there are hundreds of thousands big enough to wipe out a city," Morrison says. And too many of those remain undetected, to say nothing of even smaller but still dangerous rocks, like the one that blew up over Chelyabinsk.

"I will have to quote Don Yeomans," Morrison says, referencing one of JPL's asteroid gurus. "The first thing to do is find them. The second thing to do is to find them. The third thing to do is to find them. Then you can do all the rest — calculate orbits, predict impacts, and think about deflection. If you haven't found them, none of the rest is meaningful."

 

Keep Calm and Celebrate Asteroid Day

 

The purpose of the California Academy of Sciences is to "explore, explain, and sustain life on Earth," said Ryan Wyatt, Director of the museum's Morrison Planetarium, who opened the first-ever Asteroid Day from a small stage in the museum's atrium on the morning of June 30, 2015. "It's hard to imagine something that could be more of a threat to life as we know it than an asteroid with our name on it," he said. "As you walked in, you passed a T-Rex skeleton that welcomed you. The dinosaurs didn't do well with their asteroid."

Asteroid Day had been more than a year in the planning — conceived to raise attention to the subject of Planetary Defense by a coalition of scientists and space industry notables who have grown tired of waiting for governments to act. The point of Asteroid Day was to generate publicity, as well as to introduce the 100X Pledge, a call to action — in the form of a petition — for the world to increase its ability to detect asteroids by 100 times.

Wyatt turned the stage over to Rusty Schweickart, former Apollo astronaut and co-founder of both the Association of Space Explorers and the B612 Foundation, one of Asteroid Day's main sponsors.

"My job is to do Asteroid 101," said Schweickart, who was the first person to drive the lunar module in space. He sports an impressive shock of sweeping white hair that gives him the faint air of a Revolutionary War general, and he has the loose, easy manner of a school principal on a sitcom. Schweickart clicked through a quick history of the Solar System explaining that asteroids are pieces of planetary material that, for various reasons, "never quite got together to form planets." Most of them exist in a huge belt far out in the Solar System, but Jupiter's enormous gravity occasionally spits some of them out, where they get within closer range of Earth, and occasionally cross our orbit.

"There's a 20 percent chance of a Tunguska-sized asteroid hitting" in any given lifetime, Rusty Schweickart says.

Asteroids the size of the one that killed off the dinosaurs aren't a concern, Schweickart assured the room. "There are only 10 of them and none are going to hit the Earth." Even objects a few hundred meters wide shouldn't worry us, he said. They only hit every 300,000 years or so.

The ones that Schweickart and the rest of the Asteroid Day founders are most concerned with are the size of the one that hit Siberia in 1908. "There's a 20 percent chance of a Tunguska-sized asteroid hitting" in any given lifetime, Schweickart said. "Unless we know ahead of time and can stop it."

Asteroid Day was actually conceived by the film director Grigorij Richters and Dr. Brian May, an astrophysicist who most people know better as the lead guitarist for Queen. (Yes, you read that correctly.) Those two were in London, holding their own event, so the de facto host in San Francisco was Ed Lu. A retired astronaut who flew on two Space Shuttle missions and once spent six months living at the International Space Station, Lu says that the mystery of what killed the dinosaurs haunted him from a very early age. He has vivid memories of his favorite book, from the "How and Why Wonder" series, that was full of "fantastic drawings of dinosaurs" and ended with a cliffhanger: "'What killed off the dinosaurs? We don't know.'" Later, the Alvarez Hypothesis answered his question. "And then I got a chance to go into space and see the craters on the moon. You can even see craters on Earth from space. And you go, 'Wow.'"

In 2001, shortly after the September 11 attacks, Lu and his friend, the noted Princeton astrophysicist Piet Hut, decided to gather some other like minds and discuss the risk of asteroids and how they might be dealt with. They invited a small group of selected colleagues, including Rusty Schweickart, to the Johnson Space Center in Houston. The pitch wasn't exactly glamorous. The meeting was held on a weekend and attendees had to pay their own way. "I reserved a conference room and said, 'If you each chip in money, we can buy donuts and coffee,'" Lu recalls. "Everyone we invited showed up."

The B612 Foundation was born out of that meeting, with Lu, Schweickart, and Hut as founders. The group was named for the asteroid that had been home to the Little Prince, of children's literature fame, and for the next decade the men — who all had other jobs and pursuits — explored concepts and did research for how technology might deal with the threat.

In 2012, Lu gave a talk on planetary defense at Google, where he was head of the Advanced Products Group. He laid out the threat and told the audience that you can't deflect something you can't see, so the single most important thing anyone could do toward saving Earth from asteroids is to put an infrared telescope optimized for spotting and identifying dangerous objects into space. Unfortunately, he said, no such project existed. Afterwards, a guy approached with a question that changed the course of Lu's work: "Why don't you do it?"

Given adequate funding scientists will be able to detect all NEOs that have a high probability of hitting Earth, with ample warning, down to the size of the one that hit Tunguska, within 10 years.

That night, Lu called Schweickart, and B612 shifted focus. They would actively solicit private funds to develop a concept for a space-based infrared telescope and, ultimately, put it into orbit — the sooner the better. They called it the Sentinel Mission.

Given adequate funding, Lu says, scientists will be able to detect all NEOs that have a high probability of hitting Earth, with ample warning, down to the size of the one that hit Tunguska, within 10 years. "That's the Holy Grail," he said, during a break at Asteroid Day. To get there will require the launch of a space-based infrared telescope — either Sentinel or a competing NASA project known as NEOCAM — in combination with a massive telescope installation known as the Large Synoptic Survey Telescope (LSST) that's currently under construction in Chile, and scheduled to come online by 2020.

The biggest criticism of B612's Sentinel is that while it's a noble goal, the project is a white elephant. The price to design, build, launch, and operate the space-based telescope for 10 years is approximately $450 million. And Ed Lu's team has struggled to raise funds; as of this fall, it had just $10 million, and barring some unforeseen impetus — say, an unexpected asteroid strike on Capitol Hill — it seems unlikely that this will change soon.

Numerous stories have been written over the past year about B612's struggle for funding, but Lu is not discouraged. "The highest risk part of any project is the very beginning, the angel capital," he said. Sentinel has a feasible design, a talented board of engineers and advisors, and an industrial partner, Ball Aerospace, capable of building the telescope.

In the context of national budgets, the amounts on the table are very small. "NASA's budget is $18 billion plus per year," Lu explained. "Over the next decade, NASA will spend, without any increases, $180 billion. We're talking now a fraction of a percent. NASA spends more money on coffee and donuts."

He glanced at his watch. The break in programming was winding down and he wanted to get back upstairs to see the next speaker. "When we started talking about asteroids in 2001, nobody else was doing it," he said. "We were just shouting out into the wilderness. But look at this, today. LSST is funded, and going forward. Sentinel didn't even exist. This is all brand new."

As an astronaut, Lu has credibility. He's a very smart man esteemed by his colleagues who brings many formidable assets to the table as a spokesperson and figurehead for a movement. One of his best is what appears to be an unshakeable optimism, even when it seems unfounded. "I feel confident that the field is moving along," he says. "It's not as fast as we'd like. Everyone wants this all yesterday. Frankly, the truth is that we could get hit the day after tomorrow by something — we just don't know right now." He said this with no hint of hysteria in his voice. In fact, he was smiling.

"This is our opportunity to really take our next step as a civilization," Ed Lu said. "Think about this: We're going to change the Solar System so we don't get hit anymore. I look at this as an opportunity for humans to step forward."

"To me, this is our opportunity to really take our next step as a human species, as a civilization," he said. "Think about this: We're going to change the Solar System so we don't get hit anymore. I look at this as an opportunity for humans to step forward."

Ten minutes later, he was back onstage, closing the morning session. "The message of Asteroid Day isn't panic," he said to the assembled. "It's that we can do something. In 100 years, we can go from the first manned flight to engineering the entire Solar System to prevent asteroid impacts on our home planet." He held that thought, smiling. "The Earth will have two phases. The first is 4 billions years of random impacts." That phase killed the dinosaurs. "And the upcoming phase: A species has decided its planet should never be hit by asteroids. Science, technology and humans can actually make that happen. That's what Asteroid Day is all about."

 

Meanwhile, Back at NASA…

 

The private sector might be agitating most loudly at the moment, but what strides have been made toward defending Earth from exploding space rocks so far are almost entirely thanks to NASA. The initial Spaceguard Survey, set up to heed Congress' order to locate all NEOs one kilometer and larger, was a NASA program, and that's since grown into a small but important faction within the agency dedicated to improving Earth's defenses.

The hub is at the Jet Propulsion Laboratory (JPL), in the shady hills outside Pasadena, California. There, Paul Chodas presides over the Near Earth Object Office, a modest warren of offices where the motto is "keeping an eye on space rocks." Chodas looks like an older Sam Neill, the Kiwi actor who plays the dad on Jurassic Park, and he sits surrounded by books about asteroids and comets at a desk with views of a wooded plaza. It was a few weeks after Asteroid Day, which he skipped because he feels that the 100x Challenge is "very unrealistic, and probably not needed."

Rather than focus on finding "millions of NEOs," Chodas told me, "you want to focus on the potentially hazardous asteroids," or PHAs. Chodas has studying these objects for nearly 20 years now, since 1997, when an astronomer in Arizona spotted the asteroid XF11, causing the then-head of the Minor Planet Center to declare that it would make "an exceptionally close pass" by Earth in 2028, with a slight chance of making impact. This declaration caused a brief furor, and even made A1 of The New York Times, but a consortium of other astronomers, including Chodas, did the math and declared the risk null.

Still, the event caused NASA to establish an office that would focus solely on the search for NEOs, and serve as the agency's repository for known asteroid data. (And to speak up when a bunch of crackpots in Europe begin agitating online about a mythical asteroid impact, as they did this past August.

"It's important that we pay attention to the threat, that we search for these objects and confirm that they are not going to hit the Earth."

 — Paul Chodas

The NEO Office opened in 1999. Since then, NASA's NEO program has developed most of the tools and programs to find, track, and manage known NEOs. Until 2006, new discoveries came mostly through the LINEAR (Lincoln Near-Earth Asteroid Research network), which repurposed dozens of electro-optical telescopes developed by the Air Force to do Cold War space surveillance and used them instead to hunt asteroids. Since then, the Catalina Sky Survey in Arizona has played the most prominent role, but Pan-STARRS in Hawaii is increasingly critical.

In 1994, the comet Shoemaker-Levy 9 slammed into Jupiter — the first time humans had ever witnessed celestial bodies colliding.

JPL/NASA

It's not enough to just spot a new asteroid. In order for that observation to be useful, you need to track the object's orbit, so that you can determine where it's going in the future and how likely it is to cross paths with Earth. Close encounters aren't unique occurrences; an asteroid that just misses us is going to come close again in the future, possibly very far in the future. In the early days, these orbits had to be computed manually; today they are automated.

Every discovery made on a given night is sent to the International Astronomical Union Minor Planet Center, a five-person office based at Harvard that calls itself "the nerve center for asteroid detection in the Solar System." There, the data is collected, compared against existing NEOs, and if the object is confirmed as a new discovery, it's named, and an initial orbit is calculated. Then it's added to the public database. At the current rate, the Minor Planet Center adds more than 100 NEOs a month, most of them posing no risk to Earth.

Chodas takes note of every addition. If the data suggests that an NEO could cross Earth's orbit at some point in the future, software that runs automatically and continuously calculates when and where the object might hit. The system works. It's been road-tested; a great example is the asteroid 2008 TC3. This relatively tiny object — just three to five meters in diameter — was spotted by the Catalina Observatory outside Tucson, Arizona, less than 24 hours from impact in October 2008. Chodas' office computed its trajectory and predicted the location of impact, in northern Sudan, so precisely that scientists were able to recover the pieces from the desert floor.

But Shoemaker-Levy 9 is still the one that most stands out to Chodas. "It demonstrated that big impacts happen, and really drove home the importance of our work," he says. "But it's a very rare event. It's important that we pay attention to it, that we search for these objects and confirm that they are not going to hit the Earth. That's the most likely outcome — that they miss. But we have the telescopes and the computing power to do this, so we ought to find as many as we can."

The Spaceguard Survey was an unqualified success. But in 2005, Congress raised the stakes. It told NASA to find at least two-thirds of the NEOs 140 meters and larger — a significantly more difficult challenge. These objects are much smaller, and far more numerous. And there's a bigger problem: The program has now passed through two Presidents and still hasn't been funded. Congress wanted the survey to be completed by 2020. "We are not going to make it by 2020," Chodas said.

Chodas has watched NASA's interest in asteroids grow steadily since he's been in his chair. He's bullish about something known as the Asteroid Redirect Mission, approved but in the very early stages of planning, which will dispatch a robotic spacecraft to visit a large NEO and remove a "multi-ton chunk" from the surface. That chunk will then be brought back and placed into orbit around the moon so that astronauts can visit and study it. The point, according to NASA, is "to advance the new technologies and spaceflight experienced needed for a human mission to Mars," but it would also allow Planetary Defense scientists to study asteroid composition and behavior in a direct way — things that become very important once focus shifts from identifying asteroid threats to deciding how to deal with them.

 

Not All Asteroids Are Created Equal

 

Across JPL's campus from Chodas, research scientist Lance Benner is trying to determine the physical properties of asteroids, an important area of study that is still very much a mystery. And if the space industry is going to figure out how to deflect or destroy a threatening asteroid — once we have the ability to detect them far enough in advance — it's critical to know exactly what they're made of.

The Goldstone Deep Space Communications Complex, in California's Mojave Desert, is part of NASA's Deep Space Network. Its main purpose is to assist space missions, but Goldstone also uses radar to do detailed mapping of Near Earth Objects.

William James Warren/Getty Images

Benner is the principal investigator of a program called Radar Reconnaissance of Near Earth Asteroids that uses two primary telescopes — NASA's 70-meter Goldstone telescope in the Mojave Desert and the Arecibo Observatory in Puerto Rico. He works out of a windowless office with scuffed floors and filing cabinets that have probably been in use since before the Moon Landing.

If large objects get close enough, radar can provide an incredibly detailed picture of them. To illustrate this, Benner points to a series of such images taped to his door of actual asteroids, mapped by radar. If an object stays in view for long enough as it crosses the sky, the images captured can be used to estimate three-dimensional shapes that can then be modeled using a 3-D printer. Benner picks one such object up, a white, egg-shaped model of the asteroid Nereus. He puts that down and picks up Mithra, shaped like a dog bone, and then Toutatis, which resembles a yam, and finally the oblong-shaped Bennu, which another asteroid-centered NASA mission, known as OSIRIS-Rex, will visit in 2018.

Most asteroids are thought to be pieces of ancient space material that never formed into planets. The majority of them orbit the sun in a belt between Mars and Jupiter, but many are cast out into eccentric orbits that occasionally cross paths with planets.

Goddard Space Flight Center Conceptual Image Lab/NASA

OSIRIS-REx will study and map Bennu, then lower a robotic arm, extract, and bring back about a baseball's size worth of material, providing scientists their first-ever look at what the pristine primitive material from a solid asteroid — as opposed to the many made of loose material, and referred to "rubble piles" — looks like up close. The primary motivation for OSIRIS-REx is cosmology, to look for answers about our origins in the make-up of this ancient space rock, but one reason this particular asteroid was chosen is that, according to NASA, "it has a relatively high probability of impacting Earth late in the 22^nd Century."

The vast majority of NEO observations are made with traditional telescopes, so what is seen is just a point of light that can only be measured in terms of magnitude; that can give astronomers an approximate size, but the margin of error is huge — basically, a factor of two. As of my visit in July, Benner's department had observed 550 NEOs using radar. Radar provides a far more detailed picture of a particular object's shape and size, and can also hint at other physical properties like how rough its surface is, or its reflectivity, which relates to composition.

No two asteroids have the same spin state or rotation rate — some spin around the short axis, for instance, while others tumble, always at unique speeds — and radar can provide a fairly accurate look at those things, too. All of these factors are important when you start to look at potential mitigation strategies, most of which would attempt to deflect an asteroid by altering its trajectory in some way.

In 2004, when Toutatis passed within four moon distances from Earth, Benner used radar to observe how Earth's gravity changed the asteroid's spin. Among the goals of OSIRIS-REx mission is to measure the Yarkovsky effect. That's when an irregularly shaped object absorbs sunlight, and there is a thermal time lag between when it absorbs the sunlight and when it reradiates that heat. "It's like the afternoon effect on Earth where it's hottest in the afternoon but not at noon," Benner says. "That imparts a very gentle thrust that can change the spin. It can also change the object's trajectory." Benner's group has already observed this, with the asteroid Golevka, which corrected its course by about 15 kilometers.

Planetary Defense Conference

"The common misperception is that we are looking for them on their last final plunge," says Lance Benner. "We aren't. We want to find them decades or centuries before they actually pose a threat."

The Yarkovsky effect has actually given rise to one of the more outlandish-sounding mitigation ideas: Painting asteroids black, with the idea that a black object absorbs more heat and will later give off more heat, providing a natural booster to alter its spin and trajectory. Given enough warning, when an object needs only to be nudged to knock iT off of an Earth impact course, it could work. "It's not something that people are considering very seriously but in principle it could do it," Benner says. "Or you could cover an asteroid with talcum powder. That would change its thermal properties."

Benner isn't ruling out any of the concepts on the table. "The whole idea is to find these things so far in advance that we have plenty of time to prepare. The common misperception is that we are looking for them on their last final plunge. We aren't. We want to find them decades or centuries before they actually pose a threat."

 

We're Going to Need a Bigger Telescope

 

In the waning days of September, the Planetary Defense community got some good news, when NASA winnowed the field of potential "Discovery" mission finalists to five. The Discovery Program exists to fund less expensive space missions, with a budget of $450 million or less, and one of this year's finalists was NEOCam, the infrared telescope concept that, like B612's Sentinel, was designed to sit in space and look for asteroids. Each of the five finalists was awarded $3 million in funding for design studies and analysis, and in September 2016, one or two of those proposed missions will be approved for flight.

The home base for NEOCam is at the Infrared Processing and Analysis Center (or IPAC), a NASA JPL-affiliated office that's across Pasadena, on the campus of Cal-Tech. There, for several years, Amy Mainzer has been leading the development of NEOCam, which is the direct descendent of the Wide-Field Infrared Survey Explorer (WISE) telescope that launched in 2009, and detected 34,000 asteroids and comets in its first year.

In total, WISE found more than 160,000 asteroids, and it didn't just see them. It provided sizes, reflectivity, orbital elements, and in some cases was able to determine whether the object's surface was covered with sand or rocks. Most of those, however, are main belt asteroids and irrelevant to planetary defense. It only discovered about 135 NEOs. "It was a good prototype," Mainzer says, from her seat at a conference table at IPAC's offices. And led to some other key innovations, such as algorithms than can mine new asteroids out of the data stream in real time, so that humans aren't wasting hours deciphering what's an asteroid and what's just a star.

Alex Wong/Getty Images

"At the end of the day, it's really good that people are interested in this problem. It's a solvable problem. That's rare in science."

— Amy Mainzer

Work on WISE convinced Mainzer that she needed a better telescope — one with more precisely tuned infrared detectors and an orbit chosen specifically to look for asteroids. NEOCAM would be parked in orbit around one of the five Lagrange points between the Earth and Sun — specifically, at the first point, known as "Earth Sun L1." Find the right spot and "you can just sit out there," Mainzer says, surveying the sky 24 hours a day.

NEOCAM would sit just outside the orbit of the moon. From there, the telescope would look around the orbit of the Earth, prioritizing the search for PHAs, the ones that get really close.

This is what Chodas was getting at with his rejection of the 100x Pledge. "Not all near Earth objects are equally interesting," Mainzer explains. The ones that do matter tend to make numerous close approaches; generally speaking, they have orbits very similar to ours. And the more circular and similar the object's orbit is, the more likely it is to become a risk. "That means that they're more or less distributed around the orbit of the Earth," she says.

Mainzer expects NEOCAM to have a lifespan of at least five years. In that time, she says, "we would be able to make a significant improvement on the potentially hazardous asteroids that we know about." She is confident that they could spot two-thirds of the objects over 140 meters, meeting the Congressional mandate, if not more. And they'll "map out a whole lot of the smaller ones" in the process.

She thinks that NEOCam probably would have spotted the asteroid that exploded over Chelyabinsk a couple of months before impact. That's too late to do any mitigation, but it's ample time to prepare for civic response.

Mainzer thinks that the most important development since 1994 is the planetary defense infrastructure that's been laid — the computing resources, the network of telescopes, the increasingly connected web of groups working on the problem. "This whole system didn't exist until fairly recently. To me that's a really important accomplishment. Now, what's missing is just a sensor network. We need to add more observations.

"At the end of the day, it's really good that people are interested in this problem," she says. "It's a solvable problem. That's rare in science."

 

The Nuclear Option

 

For the sake of argument, let's say that the surveillance component of Planetary Defense is in good shape. It's far from the robust network of land- and sky-based sentries that will ultimately give us a failsafe early warning system, but at least there are many telescopes scanning the skies every night for potential dangers and more powerful tools are on the way.

But what happens if one of these telescopes spots a real danger? What if Paul Chodas runs a new discovery through his algorithm and the result is incontrovertibly terrifying? What if all of the world's astronomer's agree that an asteroid is headed our way?

Out in the arid hills east of Oakland, behind the electrified fences that protect one of America's most important and secret labs, Dave Dearborn is considering this very possibility — at least occasionally, when time permits. Dearborn is a physicist at the Lawrence Livermore National Laboratory, and one of the most experienced nuclear weapons designers on Earth.

Livermore is a secure facility, but there's a small public section known as "the High Performance Computer Innovation Center" that looks nothing likes its title. It's a small group of prefab trailers with drag interiors and that's where I met Dearborn and Megan Bruck Syal, a young researcher who works alongside him on an interesting new project for the weapons program — investigating the use of nuclear warheads as a means to destroy asteroids and save Planet Earth.

Lawrence Livermore National Laboratory

Dave Dearborn was irritated by something he heard from a scientist on NPR, who said, he recalls, "You can't use nuclear explosions. That's only Hollywood."

Dearborn is the definition of a rumpled scientist, and I mean that in the most endearing sense possible. He has a grey beard, a ruddy complexion, and a jovial manner. He could be your high school physics teacher — if your high school physics teacher were one of the few humans who has designed, built, and participated in the explosion of a nuclear weapon. Turns out he's also very interested in asteroids.

Dearborn was an attendee of the first-ever Planetary Defense Conference, a small gathering in 2004 organized by the American Institute of Aeronautics and Astronautics. Back then, the conversation was still relatively new. And Dearborn was irritated by something he heard from a scientist on NPR, who said, Dearborn recalls, "You can't use nuclear explosions. That's only Hollywood." Hoping to correct the record, Dearborn took his message to various conventions, where people would inevitably approach with dissenting opinions about nukes. "They'd say, 'You're going to break one asteroid up into a bunch of smaller asteroids!' And my immediate response was" — here he puts his hands on his head and bulges his eyes, a la Homer Simpson — "'I never thought of that!'" He laughed. "'So let's not do it the stupid way then.'"

Last year, the U.S. government announced a partnership between NASA and the National Nuclear Security Agency (NSSA), officially tasking Livermore and its two sister labs, Los Alamos and Sandia, with considering this problem. It's still a small effort. "There are about 10 of us who work on this part-time," says Dearborn. "Combined, we make up about one full-time staff person."

Media reports, especially in the science world, sometimes cast the specific planetary defense programs in isolation, as independent units pursuing their belief in the right way to do things. In truth, they're all very congenial. Dave Dearborn is happy to figure out how to shoot a nuke into space to blow up a deadly space rock, but he's also happy if ultimately we solve the problem another way.

The most widely discussed mitigation concept is what's known as a kinetic impactor, a heavy spacecraft that would be launched into space to intercept an asteroid and ram it off-course. Others scientists, including Ed Lu, have argued in favor of gravity tractors, which would use a large spacecraft's gravity to gently push or pull an asteroid out of its impact trajectory. And there's growing support for the idea of blasting NEOs with high-powered space lasers.

Nukes are a viable option... " Turns out that planetary defense is a microcosm of the weapons program," Paul Miller says.

But nukes are a viable option. Paul Miller, the Project Manager of the joint national lab program, likes to point out that Livermore and its sister labs aren't just involved because of their expertise with nuclear weapons, though that is certainly the primary reason. ("If you need a nuke," he jokes, "I know a guy.") Because of their complicated work in physics and chemistry, much of it literally on the leading edge of research, the labs have other assets they can bring to bear: multi-physics modeling, high-performance computing, algorithm development, material strength, and uncertainty quantification, to name a few. "Turns out that planetary defense is a microcosm of the weapons program," Miller says.

Dearborn says that the method we ultimately use to mitigate the threat of an asteroid bearing down on Earth will be determined by circumstances. Given enough warning, less complicated options like a kinetic impactor might be preferable. But if the object in question is detected too late, or is too large, your options shrink. Your best hope is to vaporize it.

One challenge is that the mass of things grows as the cube of the diameter, meaning that a 1,000-meter asteroid is 1,000 times more massive than a 100-meter object. So if you had a single kinetic impactor designed to ram and deflect a 100-meter rock, you'd need to launch 1000 of those impactors to handle a 1,000-meter threat. "In those cases, the nuclear option is really the only practical one that we have," Dearborn says.

It's clear that Dearborn enjoys talking about this subject and its challenges. You can hear it in his voice. Among the many complications of predicting an impact is that the study is so imprecise. The percentage chance that a particular object is headed for Earth could remain low for a long time — for years or even decades — but the longer we wait, the closer the object gets "and the amount of work you have to do to cause it to miss goes up and up," Dearborn says. But there's a problem beyond that, too. Miscalculate, and you might tear an asteroid apart instead of vaporizing it, turning a single NEO into a sea of them.

Given an emergency, I asked, does the technology exist today to put a nuclear device into space and direct it at an asteroid? "The technology exists in the sense that people have done all the pieces that need to be done," he replied. "But there is not a vehicle sitting somewhere in a warehouse that you could use." He showed me an abstract from the most recent Planetary Defense Conference, held last spring in Italy. It looked at a related question of how a standard nuclear explosive that exists in the stockpile today could be used against an actual asteroid. Dearborn's team modeled how a one-megaton device, detonated away from the surface of the asteroid Bennu — this is known as stand-off detonation, to direct a blast wave of X-rays toward the target — would affect its trajectory.

Bennu is about 500 meters in diameter and has flown close enough to be modeled; it's the target of NASA's OSIRIS-Rex mission, you might recall. "It's a big asteroid," Dearborn says. "And you have to back way off to get the right push. But yes, we have all the things we need in the active stockpile to deal with most asteroids." He smiled. "The paper was designed to show what we have in the stockpile will work for objects up to kilometers in size and that we can do it purely with the X-rays. If we had something bigger we might not be able to use what's in the stockpile but we know what to build."

"Over the next decade, NASA will spend, without any increases, $180 billion."

- Ed Lu

Getting a nuke into space isn't difficult, Dearborn says. The U.S. is adept at mounting and flying warheads of the size necessary for planetary defense, on ICBMs. Those don't work for deep space, but there's expertise in navigating armed projectiles in a vacuum. And a nuclear warhead would actually require a much smaller spacecraft than a kinetic impactor, Dearborn says, because impactors need to be massive to work. Warheads are small, making them light and cheap to launch.

Dearborn has made a request to the teams working on the OSIRIS-REx mission at JPL. The craft is designed to use optics to measure and steer as it approaches an object, but he had an idea. "I said, 'Wouldn't it be nice if you had a radar onboard that would give you that information?' We would want something to tell us, 'Okay, you are now a kilometer away. You're now 500 meters away.'" JPL agreed to add radar to the craft.

Dearborn says that a space-based nuclear test isn't necessary. He knows that the X-rays given off by an explosion in space will behave in a predictable manner. "It's not a hard problem like it is in the atmosphere. The X-rays go out. The X-rays then hit the rock."

What questions remain in his mind relate to what the rock does when it's heated to extreme temperatures. That's measurable, given the right materials, and it's something they're studying at Livermore already, both in computer models and in a lab, by blasting meteorite samples with high-powered lasers.

The nuclear option is often characterized as last-ditch. How much time would we need, theoretically, to get a mission going? In an urgent case, Dearborn said, you would survey the U.S. stockpile and find the right device. "You grab something big and say, ''Oh well, we don't need all this case, let's take it out. Here's the explosive part, let's put it in this little cocoon.' We can get a Delta 4 Heavy ready in about six months. NASA thinks it'll take them about five years to build the piece that you put on the end of the Delta 4 Heavy, though. It could be shortened from the five years if in building an impactor mission, they put a radar on it, and you said fine, 'We've now designed and built exactly the vehicle we need to carry it.'"

When I probed too excitedly about nuclear-armed space rockets, Dearborn sensed it, and dialed me back a notch. "It's always important to note that these things, while they are certain to happen with time, don't happen commonly," he said. "I've never been one to say, 'Oh God, we need to drop everything and get more funding on this till we have a good solution in hand.' Let us continue working on it at a modest pace and hopefully by the time the next one comes along we'll be ready."

 

There's More Than One Way to Vaporize An Asteroid

 

In 2008, Iowa State University created a new center for asteroid deflection research and named Professor Bong Wie as the founding director. There is no actual center, or even much of a staff. "This is just a center in cyberspace," Wie says.

Professor Wie specializes in space vehicle guidance, control, and dynamics. Nine years ago, he attended a planetary defense conference and had an epiphany. In a room full of scientists, he realized that he was one of the few engineers there. "They talked about mitigating the impact threat from a very scientific viewpoint," Wie told me. As an aerospace engineer, he thought, he could contribute. "Since that time I have made it my full effort to study the technology for deflecting or destroying asteroids."

Wie helped imagine the Hypervelocity Asteroid Intercept Vehicle, or HAIV (pronounced "high-V"), a concept designed as a way to get nuclear warheads to an asteroid that is really just a kinetic impactor with a payload. His partner on the project was a NASA engineer named Brent Barbee, and their work was funded by NASA's Innovative Advanced Concepts program, which allocates relatively small funds for experimental ideas.

The HAI-V is different from many of the other mitigation concepts being studied; it is a weapon of last resort. Impactors in most cases are viewed as ways to disrupt an asteroid's orbit by ramming it far in advance of its approach to Earth. Doing this requires a rendezvous far out in deep space. Given enough time, scientists would send a craft into orbit around the sun, headed to a point in space where, at some future time, it will cross paths with the asteroid. At that point, the craft would slow down to match the rock's velocity, and then ram it or blast it or do whatever it's supposed to do. That is a complicated and time-consuming proposition that also requires the craft to carry huge amounts of fuel so that it can slow and steer toward its target.

Planetary Defense Conference

"If I'm trying to prevent the asteroid from hitting the Earth by deflecting it, I want to hit it at least 10 years in advance," Brent Barbee explains. "I have to blow it up in little pieces."

The HAI-V, on the other hand, is an object of blunt force. It is a projectile weapon launched into space directly at an approaching rock with the idea of hitting it at extremely high speed — as in 5 to 30 kilometers-per-second. And it could be outfitted with a bonus prize: an onboard nuclear warhead meant to maximize the punch.

"If I'm trying to prevent the asteroid from hitting the Earth by deflecting it, I want to hit years and years in advance, at least 10 years, so that change in its orbit has time to grow such that it misses us," Brent Barbee explains. "If it's only a few years or months before it would hit, I don't have that luxury. I have to blow it up in little pieces. You do that with a nuclear device."

"In reality, the asteroids most likely to impact Earth are smaller than 150 meters in diameter. And we don't need a nuke to pulverize them."

Shortly before reaching its target, the HAI-V is designed to separate into two vehicles. The first is a battering ram that crashes into the asteroid and makes a crater. The second part of the craft — the one carrying the nuke — follows in at exactly the same approach trajectory and as soon as its sensors detect that it's inside the crater, the device detonates. By detonating under the surface, Barbee says, "you can blow up a given asteroid with a smaller nuclear payload than you would need if you were to try to detonate on the asteroid's surface or only a few meters away."

The concept seems to work, at least in computer simulations. And the HAI-V could be built and directed at a target using today's technology and launch methods. "Obviously there's a lot of real-world experimentation that needs to be done to validate this stuff," Barbee says. And exact details on nuclear payloads and explosions are classified. Therefore, the HAI-V-as-nuclear-taxi has been handed off to NASA, which has asked the national labs to use their supercomputers to do advanced statistical and numerical simulations of the explosions.

Lately, Wie has been focusing more on non-nuclear applications for the HAI-V. It should work just as well as a conventional weapon. And unlike kinetic impactor ideas proposed for altering asteroid trajectories, Wie is studying how they can be used, in an emergency situation, to destroy an asteroid outright.

In reality, the asteroids most likely to impact Earth — those with "the most frequent impact probability during the next 20 or maybe 100 years," as Wie puts it — are smaller than 150 meters in diameter. And we don't need a nuke to pulverize them. Which doesn't make this problem easy. A conventional impactor big enough to pulverize an asteroid would be very heavy, and require a heavy launch vehicle.

To accomplish this, the mass required is on the order of 10,000 kilograms, which is way too much for a single impactor. Instead, Wie says, the idea would be to deploy a small fleet of impactors to attack the object one after another. This allows for some of them to miss and also enhances the efficiency.

The primary engineering for such a concept already exists. Wie sent me a packet of materials that included drawings of something called the "Multiple Kill Vehicle" (or MKV), from Raytheon, designed as a U.S. anti-ballistic missile technology during the Cold War. It looks like a quiver of small rockets wrapped around a large one, and the guidance and navigation control technology has already been developed. That can be leveraged for planetary defense, Wie says. And by splitting a 10,000-kilogram payload into five launch vehicles weighing 2,000 kilograms each, you're already in the ballpark of conventional satellites sent into orbit all the time.

Mostly, Wie has looked at what passes for "last minute" in planetary defense terms. That means a few years, not a few months. "It will take about three years to design, build, and integrate [this] with a launch vehicle." To deal with anything less than that is pretty much impossible. "There's not much anybody can do, unless the whole system is pre-deployed and waiting underground in a silo like ICBMs."

Iowa State University

"Deflection is the best solution. But when we don't have sufficient warning time, what options do we have? Do nothing? Or try to break it up into many smaller pieces—some of which will hit Earth?"

— Bong Wie

Given a little more time, Wie is certain that using the HAI-V as a last-ditch effort to destroy an asteroid can work. It's not ideal. In many cases, it would turn one large asteroid into many small ones. But isn't being hit by 100 dispersed conventional bombs far better than one strike by a nuclear warhead?

"Deflection is the best solution," he says. "But when we don't have sufficient warning time, what options do we have? Do nothing? Or try to break it up into many smaller pieces — some of which will hit Earth?"

Barbee, meanwhile, is wearing other planetary defense hats. In addition to work on the HAI-V, he's contributing to both OSIRIS-Rex and the Asteroid Impact & Deflection Assessment (AIDA) mission, a joint project of NASA and the European Space Agency that's currently under consideration. He also designed the software used to track possible asteroid targets for human exploration — an automated program run by NASA's Near-Earth Program Office. It's called the Near-Earth Object Human Space Flight Accessible Target Study, or NHATS (pronounced "gnats").

That program helped to choose targets for both OSIRIS-REx and AIDA. The latter is a mission that Barbee is most excited about, because it would provide a test of humanity's ability to reach and impact a specific NEO — in this case, Didymos, an asteroid with a tiny moon orbiting it. This so-called binary asteroid presents a unique opportunity to study real-world results. The plan is to hit the smaller object with a modest size kinetic impactor, weighing about 300 kilograms. That should change its velocity only slightly, about a millimeter per second, but this change will be detectable because the period of orbit around the primary asteroid will change.

Barbee is hopeful that AIDA gets a greenlight. It would be "a fantastic experiment" to test a host of important factors involved in hitting a relatively small object with an impactor, at high speed — including guidance and control systems and the physical effects on the rock's orbit and trajectory. "We believe it will make a very measurable change in the little orbit of that little moon," he says.

Barbee understands why there's so much emphasis on discovery. He's all for beefing up our eyes on the sky. "But we've got to get out there and start test-flying these deflection and disruption concepts," he says. "I think all the technological ingredients are there to deal with this threat now. The thing that's missing is the real-world engineering of putting the pieces together and proving that it works."

When I got off the phone with him and looked at Twitter — literally within minutes — I saw something encouraging. NASA had just released pictures of the cameras for the OSIRIS-Rex spacecraft, delivered by the University of Arizona's Lunar and Planetary Laboratory. "This is another major step in preparing for our mission," said Mike Donnelly, OSIRIS-REx project manager, in a linked press released. The mission, it said, was on schedule for a Fall 2016 launch.

 

Finally, When All Else Fails, Deploy the Death Ray

 

"Nothing's hit Washington, DC, yet," says Philip Lubin, a professor of physics at the University of California-Santa Barbara. "If Chelyabinsk had been Washington, DC, you'd get funding right now." Lubin is in charge of the experimental cosmology lab at UCSB, where he oversees some very unusual planetary defense research. He's looking at our ability to use death rays to shoot rocks out of the sky. Okay, so they're not really death rays; that's just how some people on Twitter characterized Lubin's work on "directed energy" — a.k.a. lasers — as a method to disrupt or destroy NEOs ticketed for Earth.

Sonia Fernandez/UCSB

"One of the few things that brings humanity together is war. It's the nature of people," Philip Lubin explains. "They respond to threats. Maybe we could look at extraterrestrial threats as this rallying point to come together and do something."

Lubin came to the work through his research into "directed energy for terrestrial threats" — which is a polite and bureaucratic way of saying weapons research. Looking at his calculations, he began to think even bigger: "What would happen if we scaled this up and tackled an extraterrestrial threat?" The motivation wasn't all about interesting physics; it was partly philosophical. "One of the few things that brings humanity together is war. It's the nature of people," Lubin explains. "They respond to threats, and when there's a threat, they rally their resources. Maybe we could look at extraterrestrial threats as this rallying point to come together and do something."

"I tell these kids, 'We're working on something revolutionary. There's basically no one else in the world who's doing what you're doing.'"

— Philip Lubin

He recognized "pretty quickly…within a day of just noodling," that it was feasible to imagine using phased lasers to mitigate dangerous asteroids. You superheat a portion of the rock until it begins to vaporize, giving off a jet plume of heat and debris. In a sense, you're turning an asteroid into a spacecraft with that superheated material serving as a thruster that pushes the asteroid. The more you heat it, the more it moves.

He set up a directed energy laboratory and, using very modest resources, set his students free. "I tell these kids, 'We're working on something revolutionary. There's basically no one else in the world who's doing what you're doing.' It doesn't hurt that the work is fun. The students are, quite literally, vaporizing rocks with lasers."

Lubin and his students have published "many, many papers" on the feasibility of directed energy systems — upwards of 20, he estimates, "plus a chapter in a book." But the thing that got the most attention was a lab experiment they built and filmed in which a small laser blasts a small rock posing as a tiny asteroid and slows its rotation. "It's a very graphic illustration, rather than showing them a plot of thrust versus incident power," Lubin says.

They've also looked at far bigger concepts — in particular, a laser defense system that would be assembled in space to stand guard until a threat arrives. They called this system DE-STAR, and it would be comprised of a phased array of small lasers that, in total, covered about a kilometer of space.

To date, the largest structure ever assembled in orbit is the International Space Station, which is 100 meters long. A kilometer-sized system, Lubin admits, poses some challenges, but a much smaller version could be built and launched tomorrow. Provided that works, you scale up from there. "We're not actually advocating to build the big one today, but we are advocating that we begin a roadmap towards it."

Wisely, the lab has conceived of the system with multiple purposes. They've shown that the DE-STAR concept could and should have other uses that would justify its construction. For instance, to eliminate the ever-growing array of space trash that's circling earth — loose bolts, lost panels, dead satellites, debris from Chinese anti-satellite missile tests. Or, to aid in the search for extraterrestrial life. Or, my personal favorite, as a means of propulsion for spacecraft, allowing them to travel "vastly faster than any chemical propulsion system."

Having multiple uses increases the likelihood of a project actually going forward. "If you're going to embark on a large-scale system, you'd like to be able to use it," Lubin says. "It's a lot easier to sell something to the public by saying, 'This is for your protection, but in the meantime, look at all these amazing things we can do with this same technology.' That's unlike any other technology on the table that's been proposed for dealing with asteroids. They're all single-use technologies. This is not."

The largest object ever assembled in space is the 100-meter-wide International Space Station, pictured here. A phased array laser system capable of sitting in space and blasting hazardous asteroids would need to be 10 times the size.

NASA/Corbis

People have cast doubt on the idea of space lasers even in the very recent past. But the field of photonics is in what Lubin refers to as a "rapid ascent phase," especially over the past five years. Driven by significant advances in semiconductors, both the lighting and communications industries have experienced exponential improvements in power and efficiency.

"Our approach really is, Come on, stop with the, 'It's big, it's bad,'" Lubin says. "Give me the real problems." Okay, then. One would be the feasibility of building a one-kilometer installation in space. "Is building something 10 times bigger than the Space Station impossible for humanity? That's ridiculous," Lubin counters. "Frankly you'd have to be foolish to say humanity cannot do that. There are lots of technical problems that we have to solve, but there's no fundamental reason why you can't do it."

Lubin is an opinionated man who is deeply interested in the subject of planetary defense. He also has very little time for it, since there's virtually no research funding to be had. His primary job is to teach science, and do research on the origins of the Universe.

Dave Dearborn at Livermore is in much the same boat. "He's a very passionate, extraordinarily competent scientist who wants to apply his rigor to an interesting problem," says Lubin. The fact that he has even limited funding, through the new alliance between NASA and the NNSA, is a very recent development, he adds. "For years and years and years, he just struggled away by himself. This field is filled with very passionate people who are applying their talents — not because they can get money to do so or because it's going to give them a better position — but just because they think it's the right thing to do."

That's a familiar phrase. It's exactly what both Ed Lu and Rusty Schweickart had said to me. And in fact, Lubin followed the thought by using B612 as an example. "Ed Lu pounded the pavement for years trying to convince people we should go after detection more seriously. Then he gave up and just said, 'We're just going to go raise the money ourselves.'"

"Maybe Google will decide, 'Forget the government. We're going to save the Earth,'" Philip Lubin says. "Or maybe Facebook will decide that if there's no future, there's no people to log on to our social media site, so I guess we'd better do something."

Increasingly, the private sector is moving into the business of space exploration and technology, filling the void left by the slashing of NASA budgets. Elon Musk and Jeff Bezos have both founded space companies, and are each on record as stating a desire to use those companies to get to Mars. "Maybe Google will decide, 'Forget the government. We're going to save the Earth,'" Lubin says. "Or maybe Facebook will decide that if there's no future, there's no people to log on to our social media site, so I guess we'd better do something about that."

On the plus side, Lubin says, the lack of attention from the larger world of astrophysics and space tech has created a huge opportunity. And students have worn a path to his door asking to participate in space-based laser research. "They realize this is one of these interesting scientific and engineering problems that nobody's taken on. They see the field is wide open for creativity and passion ... People say, 'It's impossible to solve that problem,' and younger people answer, 'Great, that's your generation, but we're going to go out and just do this.'"

Lubin is hardly an evangelist for building space-based lasers. He's just a professor who happens to find this an intriguing possible solution to a gigantic problem that few people take seriously. "You should look at planetary defense like terrestrial defense. You have a layered system. First of all, you have to detect the threat. You have to track the treat. And then you have to mitigate the treat." Lasers are one possible way to do mitigation. Nuclear weapons are another. Gravity tractors, kinetic impactors — they're all worth studying.

And the fact that politicians don't care, or that putting nuclear warheads or powerful lasers in space is an upsetting idea, well, those aren't issues for scientists to fret over. "Basically, I just ignore the political situation," Lubin says. "I think most of us in this field do. We just assume that some day the Earth will get together and decide, 'Okay, you can sit and die, or you can do something about it.' At the moment, we don't have to make that choice. If we knew with certainty that 50 years from now, a one-kilometer-diameter asteroid was going to hit the Earth, it would be a fantastic rallying point for scientists, engineers, and politicians to come together and produce something."

 

Preparing For the Worst-Case Scenario

 

Last year, NASA formed a new department to study NEO impacts. Dave Morrison heads that office at Ames. One of its primary concerns is studying how the atmosphere affects objects of various sizes. The largest asteroids, which pose catastrophic risk, Morrison says, "punch through the atmosphere like a fist through a cobweb." But when they get down to around 100 meters in diameter or smaller — the ones most likely to hit us — the atmosphere very much comes into play. It might slow them down, break them up, or even vaporize them entirely. And because Ames has such a long history of studying this in regards to spacecraft, so NASA can build the most effective heatshields, there's already software that analyzes the effects of something hitting the atmosphere at high rates of speed.

"We can apply that to the asteroid problem," Morrison explains. "The objective is to provide decision-makers guidance when we find one of these small objects headed for us, as to how it's going to go through the atmosphere, where it's going to hit, if it's going to hit, what they need to evacuate, etc."

Given some warning, Dave Morrison says, Chelyabinsk residents could have been told to stay away from windows. Or, as a colleague, suggested: "The Russians could have set up a camp and brought tourists in to watch it from a safe distance.

Given some warning about Chelyabinsk, he says, residents could have been told to stay away from windows. One of his colleagues had a bolder suggestion: "The Russians could have set up a camp and brought tourists in to watch it from a safe distance. I'm sure they'd make many millions. And of course the scientists would all go and set up telescopes and spectrographs. Part of our research is to tell you where is a safe distance and where the biggest danger is."

The Earth's atmosphere is a natural form of planetary defense. The asteroid that arrived suddenly over Chelyabinsk exploded thousands of feet over the surface, and at a low angle, so the damage to life and property was fairly small.

The Asahi Shimbun/Getty Images(2); Oleg Kargopolov/AFP/Getty Images; Boris Kaulin/AP; Alexander Firsov/AP; Oleg Kargopolov/AFP/Getty Images

Because a detection that doesn't allow enough time to mitigate the threat is one possible outcome, it's something that Planetary Defense advocates have to plan for. And they are. Since the Chelyabinsk event, representatives from NASA have visited and briefed the Federal Emergency Management Agency (FEMA) on several occasions precisely for this reason. As the federal agency tasked with disaster response, FEMA would be responsible for evacuations and forced relocations necessitated by a predicted impact. And FEMA and NASA now have a working group in place to begin conversations about how a response would be carried out.

"Is thinking about the end of the world fun? I think it is, frankly, because we're doing something."

— Dave Morrison

Morrison says he's alternately pleased with progress and disappointed that more hasn't been done on this issue he first raised two decades ago. "I'd rather focus on being pleased," he says. "I think this has been a worthwhile way to spend my last 20 years."

He turned 75 this year and has no plans to retire. "I'm having too much fun," he says, then catches himself. "It's interesting to say fun. Is thinking about the end of the world fun? I think it is, frankly, because we're doing something. If we just sat back and said, 'Oh my god!' that would be less fun. But we don't. We're studying and we're learning things."

Morrison is encouraged that a solution is in front of us. We are poised, in the very near future, to protect our planet from this one rare but existential threat. He smiles. "With the caveat that we have no idea when the next one is ready to come down on us. It's a fantastic thing. You can't predict it."

Like others in the planetary defense community, Morrison is measured in his outlook. He thinks it's crazy that anyone doubts the legitimacy of the work, but he also understands that the world's scientists have far bigger problems. "I think absolutely the greatest risk facing the world is global warming," he says. "This is small by comparison, even though it could produce a horrible catastrophe. But the advantage of this is that the solution is purely technical. You do not have to have people change their economic structure or their political beliefs. It's a much, much easier problem. And technocrats with some help from the government can figure out how to do it. This is a global problem. But it's a global problem that a small number of technically advanced nations could deal with."

Even the United Nations, hardly a beacon of innovation, is making strides to recognize the NEO threat and put a system in place to respond to it. In true UN form, this has mostly consisted of committees that spit out committees. The one that's been tasked with doing something has the most hilariously bureaucratic name possible: Action Team 14, which is short for the Action Team on Near-Earth Objects of the UN Office for Outer Space Affairs (UNOOSA). The notable outgrowth of that is the International Asteroid Warning Network (IAWN), set up two years ago to encourage international collaboration to find, detect, track, characterize, and warn of dangerous asteroids. "Everything is going in the right direction," says Bruce Betts, Director of Science and Technology for the nonprofit space lobbying group, the Planetary Society, and a longtime advocate for planetary defense.

"The greatest risk facing the world is global warming," Dave Morrison says. "This is small by comparison, even though it could produce a horrible catastrophe. It's a much, much easier problem."

Since 1997, the Planetary Society has been handing out grants to encourage amateurs and moonlighting professionals to use their tools and expertise to help further the study of NEOs. Earlier this year, it began funding research on directed energy at two Scottish universities. The concept, known as "Laser Bees," proposes a swarm of small spacecraft armed with solar-powered lasers that could work in concert to do what Phil Lubin is proposing with his space-based phased arrays.

"It looks very promising on paper," Betts says. "I don't want to make it seem like this is something we can do tomorrow. But let's see if it's another option that does give you a big velocity change without using nuclear weapons. There is no downside to people looking into different options. The more options, the better off we are."

At last summer's International Space University, planetary defense was one of the three projects offered to the 100 elite students from around the world who attended this annual program for the next generation of space scientists.

USC Astronautical Engineering Professor Madhu Thangavelu headed that group and says that the 34 students from 17 countries were so enthusiastic about the work that he had to remind them to sleep. In addition to considering various mitigation strategies, he said, the students looked deeply at the issues of policy and awareness. They drafted plans to create UN oversight and designed a mascot — Ash the dinosaur — to be the Smokey the Bear of planetary defense. "They wanted to get out there and make it very, very public that this kind of a thing can happen, and that we don't have to wait for something to happen before we make up a strategy and even some systems," he says.

"I think that in 50 years planetary defense will be automated," Madhu Thangavelu says. "We will have systems in place that just fry these things without much fanfare. But we've got to start somewhere."

Thangavelu thinks that directed energy, which is being studied closely by the Air Force and Navy as a weapon, will ultimately be the best and most feasible solution — but probably not in the near future. "I think that in 50 years planetary defense will be automated," he says. "It won't even make the headlines because we will have systems in place that just fry these things without much fanfare. But we've got to start somewhere."

I wondered how happy some of the movement's other founders are. From where Rusty Schweickart sits, on the very front edge of the wave, does it feel like progress has been made?

On the one hand, he says, it's still a small issue. Very few nations have allocated real resources into research, and Sentinel, for all its press, is still struggling to raise funds. In September, when NASA made NEOCam a Discovery program finalist, it also ended a partnership with B612. Lu and Schweickart vowed to fight on. "If I stand back objectively, the change has been unbelievable," Schweickart told me. "There are thousands of people involved and doing all kinds of different research — some of it totally off the wall and some very solid and serious stuff."

The problem is almost uniquely difficult. The threat of a devastating asteroid strike is, as Schweickart likes to say, "very low probability, very high consequences." The chances of it happening in any one human lifetime — let alone in a single political term, which is most relevant to funding major projects — are miniscule. And yet, if it happens, a huge swath of the world's population would be adversely affected. And we are in a position to do something about it.

If you ever attend an Ed Lu talk, he'll probably show a slide of a New Yorker cartoon in which one dinosaur is saying to another, "All I'm saying is NOW is the time to develop the technology to deflect an asteroid." To which Lu added his own caption: "The dinosaurs didn't have a space program."

"There's no question in my mind that this is an obligatory legacy gift to future generations," Rusty Schweickart says. "That is why I do it and it's what we owe the future. We can predict impacts well ahead of time, we know that we can prevent them, and to not do that is just irresponsible. Our collective legacy gift to future generations of human beings, and animals for that matter, is to do this job and get it done."

* This article is part of The Code, an editorial partnership between Popular Mechanics and Ford F-150.

---

Video Credits:

Slow Asteroid - Creatas Video/Getty images

Asteroids in Our Solar System - B612 Foundation

Asteroid Impact - Image Bank Film/Getty Images

Floating Asteroid 1 - Goddard Space Flight Center Conceptual Image Lab/NASA

Osiris Rex - Goddard Space Flight Center Conceptual Image Lab/NASA

De-spinning and Spinning Up Asteroids - UCSB Experimental Cosmology Group

From Popular Mechanics @ http://www.popularmechanics.com/space/a17822/the-asteroid-hunters/

For more information about asteroids see http://nexusilluminati.blogspot.com/search/label/asteroids  

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