How We're Finding Asteroids Before They Find Us

Massive space rocks hurtle past Earth with frightening regularity. Some scientists want to deflect them. Others want to drag one closer.

Data Visualization by Jan Willem Tulp

Marco Tantardini spent the year of 2010 dreaming about asteroids. A thickly bearded, 26-year-old Italian who wore a black-leather jacket and rode a motorcycle, Tantardini looked more like Hemingway in his later years than a buttoned-down space wonk. He had done internships at The Planetary Society and NASA but those were finished. He had gotten a master’s degree in space engineering but hadn’t sought a traditional job. Instead, at his parents’ house in the Italian town of Cremona, he sat in the same room where he did his homework growing up and drafted a plan to catch an asteroid. He called the mission Sisyphus Victorious, and he believed it would be the next giant leap for human exploration.

Unlike the Sisyphus of Greek mythology, who was sentenced to endlessly push a boulder up a hill only to watch it roll back down, Tantardini developed what he thought was a successful strategy for moving a giant rock through space. He envisioned sending a spacecraft on a journey of several years to intercept a small asteroid, one 10 meters or less in diameter. The craft would capture it, possibly with a giant net, and transport it to a stable orbital location near the Earth. With the rock parked some four days of space travel away, astronauts would get their first chance to visit, study, and possibly even touch an asteroid.

On its own, Tantardini’s vision sounds quixotic, the improbable quest of an unemployed dreamer. But many accomplished scientists and engineers are busy sketching out similar plans. In 2016, NASA intends to launch OSIRIS-REx, a robotic probe that will travel to a 500-meter-wide asteroid called Bennu, scoop up soil and broken rock, and return the samples to Earth. President Obama has pledged to send astronauts to do the same by 2025. Several teams are diligently designing craft to detect rogue asteroids and intercept them before they strike Earth. And two groups of entrepreneurs, attracted to billions of dollars worth of potential minerals, have recently formed asteroid mining startups. K. Ram Shriram, a Silicon Valley investor in the budding industry, says he sees the same potential as he did in the early days of Google.

Yet of all the plans, relocating an asteroid might offer the richest rewards. Finding an appropriate target will require astronomers to search more diligently for asteroids, a boon to those concerned about planetary defense. And depositing it in the vicinity of Earth would greatly benefit scientists and miners alike, enabling them to examine it up close. When Tantardini came along with Sisyphous Victorious, it was the exact right moment to catalyze the space-science community around a wildly ambitious goal. Even he was impressed by how far it went. "When you try to do something like this, you don’t think about how unlikely it is," he says. "You just believe in the idea."

Chelyabinsk, a large city in western Russia, was best known for producing tractors and professional hockey players until the morning of February 15, 2013, when a 19-meter-wide meteor screamed through the sky and exploded with the force of 500 kilotons of TNT. The meteor generated a fireball many times brighter than the sun, so powerful it even caused sunburns. The shock wave blew out windows and knocked residents off of their feet, injuring more than 1,200. The object was the largest to strike Earth in more than a century, and scientists had not seen it coming. Instead, they had been fixated on an even larger asteroid, the 45-meter-wide 2012 DA14, which on the same day hurtled to within 18,000 miles of Earth—1/10 the distance from our planet to the moon.

The events provided a stark reminder that humanity lives amid a blizzard of flying rocks, hunks of mineral and metal shaped like balls, potatoes, and bowling pins that range from a few feet to more than 100 miles wide. As NASA’s preeminent asteroid hunter, Don Yeomans, explains, these rocks are the leftover bits and pieces that didn’t aggregate into planets when the inner solar system formed 4.6 billion years ago.

Asteroids that come within 28 million miles of our planet are known as Near-Earth Objects, or NEOs. There are millions of them, most of which originate in the main belt between the orbits of Jupiter and Mars. Despite their occasional habit of smacking into planet Earth—wiping out the dinosaurs 65 million years ago, and leveling 800 square miles of Siberian forest in 1908—very few NEOs had been identified until recently. Astronomers discovered the first one, Eros, in 1898; by 1960, they had identified just 19 more. It was only in the late 1990s, with the advent of digital imaging and computer-aided searching, that detection really picked up. Today’s search programs discover about 20 NEOs a week. Astronomers cheered when the 10,000th one was spotted last June.

Scientists have found more than 90 percent of the estimated 950 NEOs large enough to end civilization as we know it, those one kilometer wide or more. Unfortunately, they have eyes on only 40 percent of the estimated 15,000 NEOs in the 140-meter size category, any of which could take out a major metropolitan area. Of the half a million or more asteroids in the 30-meter and smaller range, only 1 percent have been charted and many could devastate a city. As Paul Chodas, a scientist at NASA’s Near-Earth Object Program Office, often says, “It feels like a shooting gallery out there and we’re right in the middle of it.”

Even during the period of relatively blissful astronomic ignorance, people recognized the need for a robust planetary-defense plan. MIT students devised one of the first concepts for a class project in 1967. Instructed to stop a 640-meter object barreling (hypothetically) toward Earth, the students formulated a plot to obliterate or deflect it with a sequence of six nuclear bombs. Blowing up a large rock, however, could just as easily splinter it into many small hazardous objects, all still on a course for Earth—a shotgun blast instead of a single bullet.

Backed by more than $600,000 in NASA funding, Bong Wie, the director of Iowa State University’s Asteroid Deflection Research Center, has recently developed a more nuanced approach. His plan involves smashing a spacecraft into an asteroid to form a crater, followed by a second spacecraft carrying a nuclear bomb. Simulations show the strategy would have 10 to 20 times more destructive impact and a better chance of demolishing the rock into harmless pieces.

The shock wave blew out windows and knocked residents off of their feet. The asteroid was the largest to strike earth in more than a century and scientists had not seen it coming.

Other experts have proposed less violent tactics. David Hyland, an aerospace engineer at Texas A&M, suggests “painting” a light or dark stripe around an asteroid. The stripe would change the object’s reflectivity so that radiating thermal photons subtly alter its path. Researchers from the University of Strathclyde and the University of Glasgow in Scotland are modeling a plan to surround a space rock with several small craft they call “laser bees.” Each would fire a laser beam at the asteroid’s surface, creating a plume of gas that, like exhaust from a rocket engine, would nudge the object off course.

But even the cleverest defenses are useless against asteroids that haven’t yet been found. “We citizens of Earth are essentially flying around the solar system with our eyes closed,” former NASA astronaut Ed Lu told Congress last year. Terrestrial telescopes must peer out through the haze of Earth’s atmosphere and can only search at night. Space-based devices, meanwhile, are often designed to scan small slices of the universe well beyond our solar system. The instrument most suited to asteroid hunting, the WISE space telescope, was designed to take in the entire celestial sky, including galaxies and stars. It was recently reactivated for a new three-year mission to search exclusively for NEOs; two of its four infrared sensors no longer work.

To help fill what it considers an obvious technological gap, the B612 Foundation (so named after the asteroid home of the Little Prince in the classic book by Antoine de Saint-Exupéry) has partnered with Ball Aerospace to build a privately funded observatory that it hopes to launch in 2018. Called the Sentinel Space Telescope Mission, it would fly in a Venus-like orbit, its infrared sensors searching for the faint heat signatures emitted by asteroids radiating solar energy. “Sentinel will be about 100 times more effective than all other observing systems combined,” says Lu, a B612 cofounder.

So far this year, the organization has raised just $20 million of the $450 million necessary to launch and operate it. While half a billion dollars is hardly pocket change, Lu points out that the cost is comparable to a mid-range civic project. For the same amount that Texas A&M is spending to renovate its football stadium, for example, scientists could launch a civilization-saving eye in the sky. “There are a lot of people who say, ‘I don’t know anyone who has been killed by an asteroid in the past 100 years, so I don’t need to worry about it,’ ” Lu says. But he compares those people to gamblers in Las Vegas. “The odds are what they are, and at some point the house always wins.”

As Tantardini worked on Sisyphus Victorious, he could look out of his window and see the 343-foot-tall Torrazzo of Cremona, a brick bell tower that had been raised in the 14th century. Inside the tower sits a large astronomical clock, and to the father-and-son team who created it, the notion of humans voyaging into space must have been imponderable. On many days, Sisyphus Victorious felt similarly unattainable to Tantardini. Friends suggested that he just write up a paper, present it at a conference, and move on. But he wasn’t willing to give up on his idea. “I wanted to make something real happen,” he says.

Tantardini knew he didn’t have the expertise to develop the mission on his own, so in the summer of 2010 he decided to recruit other engineers to help him. He reached out to acquaintances from his former internships, and he Google-stalked NASA’s top administrators, emailing them his pitch. Many of his overtures were met with silence, but some experts were interested enough to listen, among them Martin Lo, a spacecraft trajectory expert at NASA’s Jet Propulsion Laboratory (JPL), and Louis Friedman, the co-founder of The Planetary Society.

“My first reaction was, ‘Aw, move an asteroid, are you crazy?’ ” says Friedman. People have been devising various schemes to do so since at least the 1970s. They proposed using solar sails or rock-spewing mass drivers, or even engineering a collision between two objects so that they richochet off one another like a combination shot in pool. Tantardini was drawn to a more promising strategy: He expanded on calculations done by Lo in 2002 describing low-energy orbits that could be leveraged to transport an asteroid. By combining propulsion from a spacecraft with a gravity assist from bodies such as the moon, Tantardini concluded, an asteroid could actually be moved.

Intrigued, Friedman invited him to describe the concept to a group of engineers from JPL and Caltech. They in turn suggested the Keck Institute for Space Studies (KISS), an organization dedicated to developing new space mission concepts and technology, might fund a feasibility study. KISS agreed and Friedman co-led the effort. Tantardini served as one of 30 members on the study’s panel, which included Yeomans, representatives from multiple NASA mission centers, academics from Harvard and Caltech, and former astronauts.

Building on prior asteroid-relocation research, the team plotted out a mission that would send a robotic spacecraft on a three-to-five-year journey to a target NEO. They then conceived a way to capture it: Inflatable arms would deploy a giant bag, 15 meters in diameter, that would swallow the space rock like a python eating a gerbil. Cables would cinch the bag tight and the spacecraft, now spinning with the asteroid, would fire thrusters to right itself, and then begin the trip back home.

Perhaps the biggest challenge in hauling a million-pound asteroid through the solar system lies in finding capable propulsion. For that, the team looked to John Brophy, a rocket scientist at JPL and another of the study’s co-leaders. Brophy had been working on ways to move an asteroid since 2007 and had designed solar-electric-propulsion (SEP) systems that could actually get the job done. Powered by photovoltaic panels mounted to a spacecraft, SEP systems use electricity to ionize xenon gas, accelerate these ions, and fire them from the rear of the engine at speeds of up to 30 kilometers per second. “You get about 10 times the exhaust velocities as you would with a chemical propellant,” Brophy says. He designed the SEP system used on NASA’s Dawn probe, which is now on its way to the dwarf planet Ceres, and he is currently helping to develop a next-generation SEP system that is at least 20 times more powerful.

For the same amount that Texas A&M is spending to renovate its football stadium, scientists could launch a civilization-saving eye in the sky.

In 2010, Brophy and several NASA colleagues studied how a SEP-powered spacecraft might capture a 10-ton asteroid and move it to the International Space Station (ISS). Tantardini had suggested parking the asteroid at an orbitally stable Lagrange point near the moon, and the KISS team found that such a destination made practical sense. It would require much less power to move an asteroid to a Lagrange point or to high-lunar orbit, an even more stable location, than deep into Earth’s gravity well. That meant the spacecraft could grab a considerably bigger rock—up to 1,000 tons—and larger objects are easier to find and characterize.

The scientists finished the KISS feasibility study in April 2012. Inspired by the report, NASA commissioned its own team to work through the mission in even greater technical detail. In early 2013, that plan made it all the way to the White House: President Obama proposed $105 million in his 2014 budget for NASA to formally work up what the space agency was calling the Asteroid Redirect Mission (ARM). “Nobody doubted that we could eventually move an asteroid in the future,” Brophy says. “What is most startling to people is finding out that you could do it now.”

Few people are more excited by the prospect of relocating asteroids than those who want to mine them, an idea that has tempted visionaries for more than a century. The Russian rocket scientist Konstantin Tsiolkovsky wrote in 1903 that mining asteroids would be essential to the conquest of the cosmos; it would allow astronauts to live off the land, harvesting resources like hydrogen for fuel and water.

Asteroids could also make for a very big payday. According to Planetary Resources, an asteroid-mining company founded by commercial-spaceflight pioneers Peter Diamandis and Eric Anderson in 2010, a single 500-meter-wide space rock could contain 1.5 times the current world reserves of platinum-group metals like iridium and palladium. A water-rich asteroid of a similar size, meanwhile, might contain 80 times more water than a supertanker. If it were converted to hydrogen and oxygen, the company says, it could provide enough fuel to power all the rockets ever launched in human history. Attracted by the same staggering numbers, a second asteroid-mining firm, Deep Space Industries, launched in 2013.

To find such a flying treasure chest, Planetary Resources plans to launch a series of increasingly robust space telescopes. The first model, called the Arkyd-100, will be fairly humble: Its mirrors are only nine inches wide, versus the Hubble Space Telescope’s 94-inch primary mirror. But Chris Lewicki, the company’s president, believes that Arkyd will be the first step toward a new industrial revolution. “The Internet, automobiles, aviation, railroads—asteroid mining is the 21st-century equivalent of all that,” he says.

But even relatively nearby asteroids orbit millions of miles away, making them too distant for practical use. NASA’s ARM spells out a feasible and fairly affordable method for moving such objects much closer to Earth, which makes the mission intensely interesting to miners. Lewicki, who was a member of the KISS study team, praises the mission concept both for its potential to advance asteroid mining and for its sheer boldness. “NASA is talking about sending humans farther out into space than they have ever been before by orders of magnitude,” he says. “It will be true exploration, the most exciting endeavor since the Apollo program.”

When NASA announced a possible Asteroid Redirect Mission, it took many people by surprise. Al Harris, a retired NASA asteroid expert, complained that the mission was “basically wishful thinking in a lot of ways—that there’s a suitable target, that you can find it in time, that you can actually catch it if you go there and bring it back.” On Capitol Hill, the mission became a political piñata. Representative Steven Palazzo of Mississippi called it “a costly and complex distraction”; others threatened to block the funding for further study. (It was ultimately approved.) What critics didn’t initially understand was that as science fiction-ish as ARM seemed, it was technologically feasible. Grabbing a space rock, furthermore, was a Trojan horse for something even greater: ARM is arguably the only current plan to send humans back into space and put them on a path to the moon and Mars.

Consider the recent history: In 2009, the presidentially appointed Augustine Committee reported that the U.S. human spaceflight program was on an “unsustainable trajectory . . . pursuing goals that do not match allocated resources.” The following year, President Obama announced he was scrapping NASA’s Constellation program, which was supposed to return astronauts to the moon (and eventually, Mars). He instead chose to accept the committee’s recommendation to take smaller, more affordable steps that would allow NASA to incrementally develop the necessary technologies.

The first goal, Obama said, would be to visit an asteroid by 2025. But even that is beyond current capabilities. The vehicles NASA is developing for human space exploration—the Space Launch System and Orion spacecraft—are designed to take humans slightly beyond the moon, not to the belt between Mars and Jupiter. The Planetary Society’s Friedman says that this is why he became so excited when Tantardini came to him with the asteroid-retrieval idea, and why NASA ultimately became so enamored as well. The mission amounted to a spin on that old saying about Muhammad: If humans can’t go to an asteroid, then the asteroid must come to us. “It was an epiphany, an answer to the fundamental problem of the human-spaceflight program,” Friedman says. “You have a destination; it’s interesting, and it’s meaningful, and it’s scientific, and it can be done within the existing program.”

Last summer, NASA launched the Asteroid Initiative, consisting of ARM and the Asteroid Grand Challenge (AGC), to help identify NEOs for both scientific study and planetary defense. Asteroid Data Hunter, the first AGC contest series, announced in March, will award $35,000 to participants who develop algorithms that improve the asteroid-detection capabilities of ground-based telescopes.

The Near-Earth Object Program, meanwhile, has launched a system to coordinate telescopes around the world in search of an ARM-suitable asteroid—one between 4 and 10 meters across whose orbital path would make it easy to capture and redirect. NASA’s Chodas says the system has alerted them to a dozen possible candidates since it was implemented in March 2013. At the Neutral Buoyancy Laboratory at Johnson Space Center, astronauts are already training in underwater tanks, leaving a spacecraft and clambering onto the simulated surface of an asteroid.

William Gerstenmaier, who directs human exploration at NASA, believes that the mission could revolutionize humanity’s relationship to the cosmos. “This would be the first time in history that we would take an object in space and move it,” he says. “We are beginning to transform space for our own benefit.”

Tantardini, for his part, has mostly moved on to other ideas, like a consumer drone project. But he looks forward to ARM’s launch. “Three years ago, most people would have said that moving even a small asteroid was just a dream, but the team showed that it can be done,” Tantardini says. “The question is not if the mission will happen, but when.”

Asteroid Impact & Deflection Assessment

Courtesy ESA/AOES Medialab

Step One: Find Asteroids

Of the millions of asteroids that routinely fly by Earth, astronomers have so far detected only 10,000. A handful of telescopes now in development could fill in the map around our planet.

Near-Earth Object Camera (NEOCam)

Who: NASA Jet Propulsion Lab
Goal: Detect two-thirds of near-Earth objects larger than 140 meters in diameter
Status: The infrared sensor passed a critical design test; if selected by NASA's 2016 Discovery Program, the mission could launch in 2020.
Plan: NEOCam's infrared telescope will search for asteroids' thermal emissions at two wavelengths while orbiting at a stable Lagrange point. Its 14-degree field of view is many times larger than its NASA predecessor, the WISE telescope.

Asteroid Terrestrial-impact Last Alert System (ATLAS)

Who: University of Hawaii
Goal: Provide advance warning (a day to three weeks, depending on the scale) of asteroid impacts
Status: Currently under construction in Hawaii and expected to begin regular operation in 2016
Plan: Two 20-inch telescopes equipped with 110-megapixel cameras would scan the visible sky twice a night. The system would be sensitive enough to detect the equivalent of a match flame in New York viewed from San Francisco.

Arkyd-100

Who: Planetary Resources
Goal: Prospect asteroids to determine their position, composition, size, and spin rate
Status: A nanosatellite named A3 will launch later this year to test several key technologies.
Plan: The 33-pound satellite, roughly the size of a mini fridge, would orbit Earth every 90 minutes and observe asteroids through an optical telescope. A laser communication system would transmit the images back to Earth.

Step Two: Stop Rogue Rocks

When a meteor exploded above Russia last year, it generated a blast equivalent to 500,000 tons of TNT. Several efforts are underway to prevent similar objects from ever reaching Earth.

Laser Bees

Who: The Planetary Society/University of Strathclyde/University of Glasgow
Goal: Deflect asteroids 2 to 400 meters in diameter
Status: If lab tests and computer models show promise, a test flight could follow in five to 10 years.
Plan: Small spacecraft would swarm an asteroid and use lasers to zap a spot on its surface for months or years. The vaporizing rock would form a plume of superheated gas that would push the asteroid onto a new trajectory.

Hypervelocity Asteroid Intercept Vehicle

Who: Iowa State University/NASA
Goal: Destroy asteroids as large as 1,000 meters in diameter
Status: Phase 2 study will end in September. A test mission could launch within a decade.
Plan: An intercept vehicle would approach an asteroid and separate into two parts. The first part would crash into the surface to produce a crater. The second, carrying a 300 to 1,000kg nuclear bomb, would detonate inside the crater and blast the asteroid into small pieces.

Asteroid Impact & Deflection Assessment

Who: Johns Hopkins University/European Space Agency/NASA
Goal: Impact the 150-meter-diameter moon of binary asteroid system Didymos as it passes Earth
Status: NASA and ESA are conducting pre-Phase A studies. If fully funded, the two spacecraft would launch in 2020 and 2021.
Plan: A spacecraft built by Johns Hopkins would smash into the smaller asteroid and change its orbit. An ESA craft and Earth-based telescopes would survey the collision to assess its efficacy.

How To Bag An Asteroid

NASA has identified human exploration of a near-Earth object as the next step on astronauts’ path to Mars. Here’s how the Asteroid Redirect Mission could work.

Courtesy NASA

1) As early as 2018, an Atlas V rocket will launch a robotic capture spacecraft to low-Earth orbit. The craft’s 40kW solar-electric-propulsion system will boost it to high-Earth orbit. There, a lunar gravity assist will accelerate it toward a target asteroid—a 500-ton, 22-foot-diameter rock.

Courtesy NASA

2) After four years, the craft will make its final approach. When it’s within 165 feet of its target, it will release an inflatable exoskeleton that will unfurl a cylindrical capture bag made of high-strength fabric.

Courtesy NASA

3) Once the capture bag envelops the space rock, a process projected to take 90 days, the exoskeleton will deflate, cinch the fabric tight, and draw it close to the spacecraft. If the asteroid spins too fast, inflatable airbags within the capture bag will lock it in place.

Courtesy NASA

4) Over the next three to five years, the spacecraft will tow the asteroid toward the Moon. It will use another
lunar gravity assist to boost it to an extremely stable high-lunar orbit. The craft and its cargo will remain there in safekeeping.

Courtesy NASA

5) In 2025, the Orion spacecraft will launch from Earth and dock with the capture spacecraft. A two-person crew will climb up booms installed between the two vehicles to the top of the capture bag, where they will study the asteroid and collect samples.

This article originally appeared in the May 2014 issue of Popular Science.