Asteroid That Might Hit Earth Next Century to Be Visited by U of A Spacecraft in 2018
The meteor blast over Chelyabinsk, Russia on February 15, 2013, broke windows, temporarily blinded and injured people, and spread tons of rocky debris over a wide area.
It was a heaven-sent marketing coup for asteroid wonks.
Dante Lauretta, Tucson father, University of Arizona professor, and principal investigator (a.k.a. "boss") of OSIRIS-REx, a billion-dollar NASA project to return a sample of an asteroid back to Earth in 2023, remembers the day vividly.
The arrival of the 10,000-ton stony object into Earth's atmosphere that day couldn't have been better timed. In fact, it marked a coincidence of spooky proportions — a reminder of the danger that strikes from above. On that day, there were two space rocks hurtling toward Earth: one that scientists knew about, and the mystery meteoroid.
Spanish astronomers had made a stir with their discovery in February 2012 of the roughly 100-foot-wide asteroid that would be known as DA14 or Duende. The rock quickly was seen as a record-setter. Calculations of its orbit showed that on February 15 of the following year, it would pass nearer to Earth than the orbits of many manmade satellites. Nothing that big ever had been seen coming so close to our planet.
Analysis of Duende's orbit showed that it would not hit Earth in 2013, if ever. But it was a good opportunity for NASA to talk about OSIRIS-REx and the important taxpayer-funded work getting done on asteroids. A year in advance, the agency planned a media event for February 15, with officials from the Goddard Space Flight Center in Maryland. Lauretta, one of the experts to be interviewed by news organizations around the country, received some "talking points" from NASA he'd be expected to cover.
"[The space agency] said, 'This asteroid's not going to hit the Earth. It's not going to hit the space station. It's not going to hit anything we need to worry about,'" Lauretta says now.
He went over the material in a round of live shots, appearing on one local station after another, answering the same basic questions, with the main theme being: "We are safe."
But while he was on the air, another story in the Russian city of Chelyabinsk led news stations. This story also was about an asteroid. But it had audio recordings of loud booms, dash-cam shots of smoke trails in a blue sky, and news footage of broken windows and kids crying.
The Chelyabinsk "impactor" later was estimated to have been about 65 feet wide, nearly as big as Duende. But it was on a whole different trajectory and wasn't related to Duende. It had come in from the direction of the sun, hidden in the glare. An expert review of millions of telescopic images taken in the weeks leading up to the impact showed no sign of the asteroid. It had flown over the Ural Mountains just before dawn and exploded about 20 miles high with the energy equivalent of roughly 500 kilotons of TNT, or 30 times the strength of the Hiroshima bomb.
It caused $33 million in damage, knocking out the windows of thousands of apartment buildings and causing the roof of a factory to cave in. About 1,200 people ended up in hospitals with injuries including cuts from glass and skin and retina burns.
Had the rock been made of a more air-penetrating metallic composition, detonated at a much lower altitude, or come in at a steeper angle, the city of more than a million people would have fared much worse, scientists believe.
A month later, Lauretta found himself giving seminars about the OSIRIS-REx project to the White House Office of Science and Technology Policy and to the House Science, Space, and Technology Committee. A favorite prop of everyone at these events was the passing around of a fragment of the Chelyabinsk meteorite. (The "-ite" gets added to these objects once they're on the ground.) The biggest known impact from space since the 1908 Tunguska event in Siberia had brought the issue of asteroids into sharp, mainstream focus.
"All of a sudden, the politicians know who we are and think we're important," Lauretta says with a grin from his office at the U of A's Michael J. Drake Building in Tucson, where researchers and students are building scientific instruments that in two years will start flying to asteroid Bennu.
Featuring the disaster-movie angle of comets and asteroids is one way to get attention for expensive space missions — but it's not hype.
More than 100 tons of space rocks enter the Earth's atmosphere every day, mostly specks of dust or material the size of a grain of sand that burns up in a flash. Every now and then, something larger cruises in.
It's a well-known scenario and a staple of the disaster genre. You've probably seen one of the many this-could-really-happen popcorn flicks about asteroids or comets threatening Earth, including Armageddon, Deep Impact, Meteor, Asteroid, or the one whose plot has Phoenix destroyed, A Fire in the Sky.
One real-life version already is unfolding, albeit on a comfortably long timescale.
Bennu, which used to have the eye-glazing name of "101955 (1999 RQ36)" before 9-year-old Michael Puzio from North Carolina won a naming contest last year, has a diameter of almost 1,600 feet. That's taller than the vertical gain of Camelback Mountain. Its orbit occasionally crosses the Earth's orbit.
During eight close calls of Earth the asteroid will make between 2169 and 2199, it has a 1-in-1,410 chance of hitting this planet, according to NASA's Sentry Risk Table.
Nothing to lose sleep over now. But those odds, combined with the sheer size of the thing, make it the perfect target for observation. Bennu's the largest object known that might hit the Earth the soonest. It's the number-two body on the NASA risk table. Number one is 1950 DA, nearly three times bigger and with a 1-in-4,000 chance of slamming into Earth — but not until the year 2880, when our ability to deal with such things may be much improved.
Bennu's not a dreaded "planet killer," like the six-mile-wide rock believed to have done in the dinosaurs. But it's big enough to cause real damage. If Bennu had hit Chelyabinsk, the city would have been wiped off the map as if from a thermonuclear weapon, minus the poisonous radiation and fallout.
The online simulator Impact Earth!, created by Purdue University scientists in 2010, helps estimate the potential destruction. Plug in Bennu's size, estimated density (currently unknown, but thought to be somewhere between "ice" and "porous rock" on the impact calculator), estimated speed at impact, and how far you'd be standing from the blast site.
Ten kilometers (6.2 miles) would be much too close. Nearly everything at that distance would burst into flame, the site calculates. A shock blast would follow 30 seconds later, flattening buildings and tossing cars like soccer balls.
Learning more about Bennu clearly is prudent, especially if the people of Earth want to prevent such a disaster. Since it's an object that orbits the sun near Earth, Bennu will teach humans how not only to deflect its trajectory but ward off other potential threats.
About 94 percent of the estimated number of near-Earth objects of truly scary size — about a kilometer across — already have been located in space. But that leaves quite a few potential Earth-smackers, and there are endless opportunities for bodies from farther out to move closer, kicked in by the gravity of Jupiter and other planets or nearby stars.
If an Earth-bound asteroid is spotted far enough out, scientists are laboring to give humans plenty of time to nudge it a little, changing its trajectory just enough to make a difference over millions of miles traveled.
NASA is funding plans to use nuclear weapons for just that purpose, similar to the plot of Armageddon, released in 1998.
But before anything like this can happen, scientists must learn more about these super-abundant space objects. Enter OSIRIS-REx, a boxy spacecraft with wing-like solar panels, a movable appendage that blows air like an elephant's trunk, and a saucer-shaped cargo carrier.
For scientists and astronomy lovers, the most interesting part of the mission isn't the chance of an impact by Bennu but the far better odds of advancing scientific knowledge. While asteroids have been known since the first one, Ceres, was discovered in 1801 by Giuseppe Piazzi, the field of study matured in the 1990s, as computer-aided astronomy began taking off. Scientists have learned that asteroids, comets, and other minor bodies are far more interesting and varied, and that near-Earth objects are more common than first thought. Some believe asteroids are responsible for Earth's water — and, indirectly, its life.
What Bennu's made of, how calculations of its orbit can be refined, and whether the recovered physical sample will match up with other astronomical observations are questions that OSIRIS-REx will help answer.
That, in turn, will fill in some blanks of one of the most pressing mysteries in the study of the outer space: How the solar system's planets, moons, and other bodies formed into their present compositions out of spinning gas and dust nearly five billion years ago.
Much has been learned in the past 20 years, with the detection and discovery of numerous planets outside our solar system around nearby stars and by the intense focus on smaller objects in our own system. Previous theories of solar system formation don't match up with what's now seen in these faraway planets and nearby asteroids and comets.
The view of the solar system still is under development, and asteroids figure large in the new theories. They can be as small as boulders or as large as Ceres, which is more like a planet. They're shaped like crude spheres, but also like dumbbells or bowling pins. Some appear reddish, deep black, or brown, and some consist of rubble held together loosely by gravity instead of solid rock or metals. They might be rich in precious metals like platinum. Even small asteroids might have one or more smaller moons orbiting about them.
Near-Earth Objects, or NEOs, have orbits around the sun and are most hazardous to humans. A comet from a distant corner of the solar system could fly in and hit Earth, but that's considered less likely than a strike by an NEO.
Back in the earliest days of the solar system, about half a billion years after the sun began shining and the planets cooled, asteroids pummeled the planet in what's known as the Late Heavy Bombardment.
Renu Malhotra, a U of A professor of planetary sciences, wrote a groundbreaking paper in 1993 suggesting that the bombardment was caused by the "migration" of the outer planets to orbits farther from the sun. A sizable portion of the asteroid belt between Jupiter and Mars fell inward, hitting Earth (among other things) with extra water and organic molecules that are the so-called building blocks of life.
"Asteroids are a double-edge sword," says Malhotra, who's working on how to refine the calculations of their orbits. "They can bring organic material and kick-start life. Then, later on, you can have a big asteroid come and wipe out life."
But not if we can do something about it.
The bright fireball that raced across the Tucson sky on the evening of December 10 won't soon be forgotten by the hundreds of people who saw — and heard — it.
"We felt this absolutely tremendous explosion . . . It shook the windows. It shook everything in the house," Tucson resident Tony Kubrak told a local TV station; his comments were broadcast nationwide by CNN. After hearing the noise, Kubrak said, he went outside: "I see this tremendous white bright light in the western sky."
(It's unclear why Kubrak would hear the noise before seeing the flash, since sound moves much slower than light. He didn't return a call from New Times.)
Some witnesses reported that the meteor looked green; one said it was orange and red.
The size of the object that caused all the fuss, experts say, probably was no bigger than a basketball. No fragments of it were found, though numerous meteorite aficionados combed the desert looking for them.
A fireball, also known as a bolide event if it occurs with a noticeable explosion, is nature's fireworks show. Fireballs stretch far across the night sky and may leave long smoke trails, commanding the attention of those below in their brief life.
The light streaks of meteors and explosions caused by bigger space objects has to do with their great speed. Bennu, for example, is tumbling through space at more than 60,000 miles per hour. In comparison, a bullet from an AK-47 flies at a relative snail's pace, about 1,600 miles per hour. Fortunately, most objects that hit Earth aren't Bennu-size or even as large as the one that hit Chelyabinsk. But a rain of rock always is falling.
The Catalina Sky Survey, a U of A project that began in 1998, finds an average of more than one per night. From one of the project's telescopes in the Catalina Mountains, astronomer Rich Kowalski discovered the first asteroid in 2014 in the first few minutes of New Year's Day, hours before the rock exploded over the Atlantic Ocean.
Not long after reporting its position to the International Astronomical Union Minor Planet Center, other scientists calculated that "2014 AA" would hit the planet. The size of a small car, the object is believed to have gone down between Central America and East Africa. No doubt, it created a huge fireball — but no cruise-ship passenger, airline pilot, or anyone else reported seeing it.
It was only the second discovery ever made of an impacting asteroid. Kowalski, who's also a flight instructor and photographer, made the first one, too. He found a 13-footer in 2008 that exploded over Sudan. It was the first asteroid ever to hit the ground that first had been tracked by telescope.
Funding for asteroid-hunting programs in the United States stood at $4.5 million a year until 2010, says Stephen Larson, the project's co-chief. After 2010, it went up to $10 million annually, and astronomers began looking more intently for asteroids as small as 100 meters across.
"These could be a problem for cities," Larson says.
After Chelyabinsk, NASA upped the funding for asteroid sky surveys to $20 million a year. The average yearly budget for the CSS has been about $1 million a year for the past six years.
"Chelyabinsk was probably the best thing we could have asked for," he says. "There were no deaths, but it was close enough to scare people."
Tracking asteroids such as 2014 AA is crucial to helping people move quickly from identification of an Earth-bound rock to figuring out exactly where it will land, Larson says. The whole concept of sky surveys is to "give us time to deflect . . . large objects," he says.
Although Earthlings haven't figured out how to deflect large asteroids just yet, advance warning that one is headed toward a city would give inhabitants time to flee, Larson says.
OSIRIS-REx, the heavily contrived acronym of the U of A project, has a nice ring to it. Osiris was the name the ancient Egyptians gave to their god of the dead. What the acronym stands for is harder to swallow: "Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer."
The project comes as part of a long line of U of A-assisted space missions and asteroid hunting. The university began a serious search for hazardous asteroids at Kitt Peak beginning in 1980 and had important roles in such deep-space explorers as the Voyager spacecraft and Mars probes.
The Kuiper Belt, a collection past the orbit of Neptune, takes its name from U of A astronomer Gerard Kuiper. Michael Drake, another legend in the field, was the university's Lunar and Planetary Laboratory director from 1994 until his death in 2011 and served as principal investigator to the OSIRIS-REx program before Lauretta.
Drake began pushing for the U of A to win the asteroid-sampling mission after it was proposed by aerospace company Lockheed Martin and NASA in 2004. The university's concept-study report initially was rejected in favor of another school's plan in the competitive process that Lauretta likened to the NCAA basketball tournament. Except it goes on for years.
"2004 to 2011 was all proposal writing, concept development, sales pitching, and marketing to [NASA] to convince it this was the best mission to fly," Lauretta says of the U of A's efforts. The space agency agreed to let the university lead OSIRIS-REx in May 2011, four months before Drake died from a prolonged illness. Two more years of planning ensued. Finally, in May 2013, LPL's proposal was approved and green-lighted for a 2016 launch.
More than 100 people are working on the project in the Drake building, more than half of them students.
On December 9, Lauretta hung a digital timer on the wall of the building's front office and began a 999-day countdown.
Assuming all goes well, the spacecraft will launch in about two years, arrive at Bennu in 2018, perform its nail-biting touch-and-grab maneuver sometime in 2019, and deliver its package back to Earth in 2023, after which the university is slated to analyze the sample for two more years.
"This defines my career," says Lauretta, 43. He has a wife and two young boys, ages 5 and 7. "We're talking 22 years from concept to end of mission. I don't know what'll be left in me by then."
He's an energetic type, though — and asteroids will be one of the hottest tickets in space exploration for the foreseeable future. Several other asteroid missions also are in progress.
NASA's half-billion-dollar unmanned Dawn mission, which left orbit from the asteroid Vesta in 2012, is expected to go into orbit in 2015 around Ceres. These are the two biggest objects in the asteroid belt between Mars and Jupiter, with diameters of about 300 and 600 miles, respectively.
The Rosetta spacecraft, a $1 billion project of the European Space Agency, was launched in 2004 and flew by asteroids in 2008 and 2010. It just came out of hibernation on January 20 and is preparing to orbit Comet Churyumov-Gerasimenko in May before it drops a lander on the comet's surface on November 11.
Meanwhile, concept plans are proceeding on a bold project announced by President Obama in 2010 to use a robotic craft to capture a small asteroid and place it in the moon's orbit before astronauts travel there to examine it sometime between 2021 and 2025.
The missions will expand scientific knowledge and usher in an age in which asteroids would be used as stepping stones for missions to Mars and beyond or even be mined commercially.
OSIRIS-REx will help bring about this new era — with the bonus that someday it might actually save lives.
The stubby spacecraft will start taking pictures on its approach while Bennu still is just a dot in the black of space. Then, from a distance of 200 meters from the asteroid, it will take extreme close-ups that can resolve pebbles on the asteroid's surface.
Three rugged one-megapixel cameras under construction in the Drake building are among the instruments the spacecraft will carry. Another is a mineral spotter being designed by a group led by Philip Christensen at Arizona State University.
One of the most anticipated findings has to do with the Yarkovsky effect on the asteroid. Because asteroids rotate like planets and moons, one side always is either heating in the sun or cooling in the shade. The heat thrown back into space from the surface acts as a thruster. An asteroid's gravity is so weak that even this tiny force has a measurable effect on the body's orbit around the sun. Lack of knowledge about the effect adds uncertainty about the precise orbit of a potentially hazardous object and whether it will hit Earth.
Six close flybys of Bennu are planned to map the perfect touchdown spot. When NASA experts sign off on the landing zone, OSIRIS-REx will descend toward the surface for its grand performance.
Bennu's gravity is so weak that walking on it would be impossible even if the surface were compact enough for a stroll. A single step would launch an astronaut out of the asteroid's orbital influence and into deep space.
Using tiny bursts from its rocket thrusters, the spacecraft is to descend to the asteroid's surface.
The plan is for the end of the robot arm to touch the asteroid for about five seconds. A gust of nitrogen gas will stir up gravel and suck it into a small chamber, to be deposited into a return capsule. When the spacecraft approaches Earth's atmosphere a few years after contact with Bennu, the capsule would be ejected, fall to Earth, and get picked up by scientists. After ejecting the capsule, the spacecraft is to permanently orbit the sun.
Researchers can't wait to get their hands on what will be the first sample brought back from an asteroid, composed mostly of carbon-based material rather than metals or rock. A Japanese spacecraft, the Hayabusa, returned dust collected from stony asteroid Itokawa (which has no risk of Earth collision) in 2010.
Analyzing the sample is where the "spectral interpretation" part of the spacecraft's name comes in. There are up to 800,000 known asteroids, but most will be studied only with a telescope, of course. Bennu has been studied more than most.
The up-close imaging and direct sampling of the small rocks, gravel, and dust (the regolith) on the asteroid's surface will be compared with information already gleaned from Bennu by telescopes. This telescope data will be "ground-truthed" by what minerals are found in the sample, meaning "we've improved our ability to interpret the spectra of asteroids across the solar system," Lauretta says.
Thanks to a 1978 made-for-TV movie called A Fire in the Sky, we more easily can imagine what a comet strike on Phoenix would be like.
A promo clip on YouTube includes a scene of the comet hitting what looks to be lower west side of the city, followed by the destruction of the Hyatt Regency building.
"Phoenix lay gutted and dead under the immense desert sky, all its splendors ruined, all its towers of glass and steel crushed and devastated," reads a passage near the end of the movie's novelization, released the same year.
The likelihood of any particular city getting destroyed by an impact from space is slim. Water covers more than two-thirds of Earth's surface, making an ocean strike a better bet. Yet because a large impact would be so destructive, some experts believe the odds of any one of us dying in a comet strike can be compared to other causes of death.
Estimates vary hugely: One estimate on a Tulane University website gives lower odds of 1 in 3,000 for each person on Earth (making death by drowning less likely) to 1 in 250,000, still far less than death by botulism or shark attack. Last year, the economist.com article stated that impact death is a long shot, with 75 million-to-1 odds, though that still beats the chances of winning a Powerball jackpot.
"An impact by an object a kilometer or two in diameter could kill about a billion people and happen once in a million years on average," writes Donald Yeomans in the 2013 book Near-Earth Objects: Finding Them Before They Find Us.
Yeomans, manager of NASA's Near-Earth Object Program Office, believes that a large impact would "have the capacity to reduce large regions of the Earth's surface to ashes and create another extinction event. We cannot afford to play the odds when civilization is at stake."
About 50,000 years ago, the mile-wide Meteor Crater near Winslow was carved out in 10 seconds by a nickel-iron asteroid about 150 feet long, evidence shows. It's impossible for anyone who's seen movies like A Fire in the Sky to stand on its windy rim and not think about how the crater would look in the middle of a city.
Not that long ago, scientists thought strikes like the one that shook Chelyabinsk occur once a century, but new research moves that up to once every 50 years, or less, says Jay Melosh, a former geophysicist and asteroid researcher at the U of A who now works at Purdue (where, among his many tasks, he helped build the aforementioned impact-calculating website).
Though the biggest space rocks present the worst threats, the "most likely" impact scenario may be from these lesser bodies, he believes.
"Expect a very strong airburst, something that breaks windows, maybe kills people on the ground," Melosh says. "The civil-defense thing to do is tell people to get away from the windows."
Melosh doesn't expect a relatively small mass to hit the ocean and cause a tsunami that wreaks havoc on coastal cities, something seen in the 1998 movie Deep Impact. Research by Melosh and others, based on previous underwater-detonation tests by the United States, seems to prove that asteroid-caused tsunami waves would break early and lose their energy.
The scariest impact scenario resembles what caused a 110-mile-wide crater 65 million years ago near what is now Chicxulub, a small Mexican town on the Yucatán Peninsula.
The impact rock was thought to have been about six miles wide. The problem for animals and plants worldwide wasn't merely the gigantic blast site, which had to have knocked over trees for thousands of miles in every direction. It was the mind-boggling mass of fiery "ejecta" that rose from the site in a plume, then descended all over the Earth at speeds exceeding 17,000 miles an hour, pummeling and burning everything it touched.
"The [heat] radiation would have been comparable to a pizza oven," he says. "Every animal with a body mass of 15 kilograms or more became extinct."
And not just the dinosaurs were cooked. Ocean animals fared poorly in the boiling water near the surface. "Nearly every species" died off following the event, Melosh says.
Burrowing animals, like small mammals, were among the survivors — and some of them evolved into humans.
Melosh is against the idea of using nuclear weapons to deflect Earth-bound asteroids, and he's wary of a deal inked in September between the United States and Russia that expands research along those lines: "I think some of this is being used as an excuse" to conduct nuclear tests in space."
Still, he's not willing to say NASA has exaggerated the threat of impacts. He just thinks deflection can be done by other means, such as ramming an asteroid with an unmanned kamikaze spacecraft.
NASA has given at least $700,000 in grants to a program led by Professor Bong Wie at Iowa State University's Asteroid Deflection Research Center. Wie and his study team, including scientists with the Goddard center, are developing a system that would punch a hole in an asteroid and then follow up by battering a second spacecraft loaded with nuclear weapons into the mass.
A study plan for the "Hypervelocity Asteroid Intercept Vehicle" was developed in 2011. "Despite the uncertainties inherent to the nuclear-disruption approach, disruption can become an effective strategy if most fragments disperse . . . so that a very small number of fragments impacts the Earth," says a write-up about the project on nasa.gov.
Though only on the drawing board, the proposed system "offers a potential breakthrough or great leap in mission capabilities," NASA says. "The proposed HAIV system will become essential for reliably mitigating the most probable impact threat: NEOs with warning times shorter than 10 years."
Sounds like a cliffhanger.
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